A review of polymer dissolution

Impact of Porosity and Stiffness of 3D Printed Polycaprolactone Scaffolds on Osteogenic Differentiation of Human Mesenchymal Stromal Cells and Activation of Dendritic Cells

Despite the potential of extrusion-based printing of thermoplastic polymers in bone tissue engineering, the inherent nonporous stiff nature of the printed filaments may elicit immune responses that influence bone regeneration. In this study, bone scaffolds made of polycaprolactone (PCL) filaments with different internal microporosity and stiffness was 3D-printed. It was achieved by combining three fabrication techniques, salt leaching and 3D printing at either low or high temperatures (LT/HT) with or without nonsolvent induced phase separation (NIPS). Printing PCL at HT resulted in stiff scaffolds (modulus of elasticity (E): 403 ± 19 MPa and strain: 6.6 ± 0.1%), while NIPS-based printing at LT produced less stiff and highly flexible scaffolds (E: 53 ± 10 MPa and strain: 435 ± 105%). Moreover, the introduction of porosity by salt leaching in the printed filaments significantly changed the mechanical properties and degradation rate of the scaffolds. Furthermore, this study aimed to show how these variations influence proliferation and osteogenic differentiation of human bone marrow-derived mesenchymal stromal cells (hBMSC) and the maturation and activation of human monocyte-derived dendritic cells (Mo-DC). The cytocompatibility of the printed scaffolds was confirmed by live-dead imaging, metabolic activity measurement, and the continuous proliferation of hBMSC over 14 days. While all scaffolds facilitated the expression of osteogenic markers (RUNX2 and Collagen I) from hBMSC as detected through immunofluorescence staining, the variation in porosity and stiffness notably influenced the early and late mineralization. Furthermore, the flexible LT scaffolds, with porosity induced by NIPS and salt leaching, stimulated Mo-DC to adopt a pro-inflammatory phenotype marked by a significant increase in the expression of IL1B and TNF genes, alongside decreased expression of anti-inflammatory markers, IL10 and TGF1B. Altogether, the results of the current study demonstrate the importance of tailoring porosity and stiffness of PCL scaffolds to direct their biological performance toward a more immune-mediated bone healing process.

Dissolution Mechanisms of Amorphous Solid Dispersions: Role of Polymer Molecular Weight and Identification of a New Failure Mode

The mechanisms of drug release from amorphous solid dispersions (ASDs) are complex and not fully explored, making it difficult to optimize for in vivo performance. A recurring behavior has been the limit of congruency (LoC), a drug loading above which the ASD surface forms an amorphous drug-rich barrier in the presence of water, which hinders release, especially in non-sink conditions. Drug-polymer interactions and drug glass transition temperature were reported to affect the LoC. However, the effect of polymer molecular weight has not been explored. ASDs of clotrimazole and different molecular weight grades of PVP were studied for their release to obtain their LoC drug loadings. Failure modes underpinning the LoC were investigated using fluorescence confocal microscopy to analyze the ASD/solution interface and phase behavior of ASD films at high relative humidity. ASDs with good release formed stable drug-rich nanodroplets at the ASD/solution interface, while ASDs with poor release were limited by one of two failure modes, depending on PVP molecular weight. In Failure Mode I the nanodroplets quickly agglomerated, while in Failure Mode II the system underwent phase inversion. This work highlights the importance of identifying the mechanisms underlying the LoC to improve the release of higher drug loading ASDs.

Microscope-enabled disc dissolution system: Concordance between drug and polymer dissolution from an amorphous solid dispersion disc and visual disc degradation

A microscopic erosion time test was recently described to anticipate amorphous solid dispersion (ASD) drug load dispersibility limit, using 0.5 ml media volume. Studies here build upon this microscope-enabled method but focus on drug and polymer dissolution from an ASD disc, along with imaging. The objective was 1) to design and build a microscope-enabled disc dissolution system (MeDDiS) with a 900 mL dissolution volume and 2) assess the ability of MeDDiS imaging of dissolving discs to provide concordance with measured drug and polymer dissolution profiles. MeDDiS employed a digital microscope to image ASD discs and a one-liter vessel for dissolution. ASD discs containing ritonavir (5-50 % drug load) and PVPVA were fabricated and subjected to in vitro dissolution using MeDDiS, where disc diameter was quantified with time. Ritonavir and PVPVA release were also measured. Results indicate concordance between imaging and dissolution. Both found 25 % drug load to provide high drug and polymer release, but 30 % yielded low release. Quantitatively, MeDDiS images predicted drug and polymer release profiles, both above and below the drug load cliff. Overall, studies here describe a MeDDiS which has promised to anticipate drug and polymer dissolution, via imaging of dissolving discs, above and below the ASD drug load cliff.

Dissolution of copovidone-based amorphous solid dispersions: Influence of atomic layer coating, hydration kinetics, and formulation

Atomic layer coating (ALC) is an emerging, solvent-free technique to coat amorphous solid dispersion (ASD) particles with a nanolayer ceramic coating that has been shown to improve powder characteristics and limit drug crystallization. Herein, we evaluate the impact of aluminum oxide coatings with varying thickness and conformality on the release behavior of ritonavir/copovidone ASDs. Release performance of powders, neat tablets, and formulated tablets was studied. Confocal fluorescence microscopy (CFM) was used to visualize particle hydration and phase separation during immersion of the ASD in aqueous media. CFM revealed particle hydration requires defects for solvent penetration, but coatings, regardless of thickness, had minor impacts on powder dissolution provided defects were present. In tablets where less surface area is exposed to the dissolution media due to gel formation, slowed hydration kinetics resulted in phase separation of the drug from the polymer in coated samples, limiting release. Formulation with two superdisintegrants, crospovidone and croscarmellose sodium, as well as lactose achieved ∼90% release in less than 10 minutes, matching the uncoated ASD particles of the same formulation. This study highlights the importance of hydration rate, as well as the utility of confocal fluorescence microscopy to provide insight into release and phase behavior of ASDs.

More Efficient Chemical Recycling of Poly(Ethylene Terephthalate) by Intercepting Intermediates

The research presented in this paper offers insight into the availability of intermediates in the depolymerization of polyethylene terephthalate (PET) to be used as feedstock to create value-added products. Monitoring the dispersity, molecular weight, end groups, and crystallinity of reaction intermediates during the heterogeneous depolymerization of PET offers insight into the mechanism by which the polymer chains evolve during the reaction. Our results show dispersity decreases and crystallinity increases while the yield of insoluble PET remains high early in the reaction. Our interpretation of this data depicts a mechanism where chain scission targets amorphous tie chains between crystalline phases. Targeting the tie-chains lowers the Mn of the polymer without changing the amount of recovered polymer flake. Chain scission of tie-chains and isolating highly crystalline PET lowers the dispersity (Đ) of the polymer chains, as the size of the crystalline lamellae guides the molecular weight of the depolymerized oligomers. When sufficient end groups of PET chains are converted to alcohol groups, the PET flakes break apart into highly crystalline and less disperse polymer. Our results also demonstrate that the oligomeric depolymerization intermediates are readily repolymerized, offering new opportunities to chemically recycle PET more effectively and efficiently, from both an energy and purification standpoint.

Converting Waste Polyethylene Terephthalate to High Value Monomers by Synergistic Catalysts

Waste plastics accumulation, such as commonly used polyethylene terephthalate (PET), has caused serious environmental pollution and resource squander. Glycolysis is a reliable closed-loop PET recycling method, which limited by the high cost and complex catalysts preparation processes. Here we report a simple synergistic catalytic strategy by premixing zinc acetate and cheap alkalis in ethylene glycol, which could achieve complete glycolysis at 180 °C within 2 hours, and a bis(hydroxyethyl) terephthalate (BHET) yield of 86.4 %. This may be attributed to the free hydroxide ions not only enhancing the nucleophilicity of oxygen in ethylene glycol and making it easy to attack carbonyl groups, but also accelerating the swelling and dissolution of PET. Meanwhile, the in-situ generated Zn-glycolate and zinc oxide nanoparticles (ZnO NPs) activated the oxygen in the carbonyl group, making the carbon cations more electropositive. Further recycling experiments and techno-economic analysis indicated that our synergistic strategy significantly reduced industrial costs and expected to achieve large-scale industrial applications.

Solvent-Activated Transformation of Polymer Configurations for Advancing the Interfacial Reliability of Perovskite Photovoltaics

Organic materials have been widely used as the charge transport layers in perovskite solar cells due to their structural versatility and solution processability. However, their low surface energy usually causes unsatisfactory thin-film wettability in contact with the perovskite solution, which limits the interfacial performance of the photovoltaic devices. Although solvent post-treatment could occasionally regulate the wetting behavior of organic films, the mechanism of the solid-liquid interaction is still unclear. Here, we present evidence of a possible correlation between the solvent and the wettability of a conventional polymer, poly[bis(4-phenyl) (2,4,6-trimethylphenyl) amine] (PTAA), and reveal the critical roles of Hansen solubility parameters (HSPs) of solvents in wetting mechanisms. Our results suggest that the conventional solvent N,N-dimethylformamide (DMF) improves the wettability of PTAA by the morphological disruption mechanism but negatively impacts interfacial charge collection and stability. In contrast, 2-methoxyethanol (2-Me) with an appropriate HSP value induces the transformation of the PTAA configuration in an orderly manner, which simultaneously improves the wetting property and maintains the film topography. After careful optimization of the surface conformation of the PTAA film, both perovskite crystallization and interfacial compatibility have been enhanced. Benefiting from superior interfacial properties, the perovskite solar cells based on 2-Me deliver a champion efficiency of 24.15% compared to 21.4% for DMF-based ones. More encouragingly, the use of 2-Me minimizes the perovskite buried interfacial defects, enabling the unencapsulated devices to maintain about 95% of their initial efficiencies after light illumination for 1100 h. The present study demonstrates the high effectiveness of solvent-polymer interaction for adjusting interfacial properties and strengthening the robustness of perovskite solar cells.

Improving the Monophenolic Yield of Lignin Depolymerization in Dualistic Aprotic Solvent System by Organic Solvent Fractionation

Converting lignin into aromatic chemicals is a promising strategy for the high-value utilization of lignocellulosic feedstock. However, the inherent heterogeneity of lignin poses a significant obstacle to achieving efficient conversion and optimal product yields within bio-refinery systems. Herein, we employed a one-step fractionation method to enhance lignin homogeneity and utilized the THF/DMSO-EtONa (tetrahydrofuran/dimethyl sulfoxide-sodium ethoxide) system to depolymerize the fractionated lignin. Three protic and three aprotic solvents were used for fractionation. The impact of the solvent properties on the structure and the depolymerization efficiency of the fractionated lignin was investigated. Methanol-fractionated lignin generated the benzoic acid compounds with a yield of 30 wt%, 50 % higher than that of the unfractionated lignin. The polarities (δP), hydrogen bonding abilities (δH), and viscosities (η) of selected protic solvents showed strong linear correlation with molecular weight (Mw), polymer dispersity index (PDI), and syringyl/guaiacyl ratio (S/G ratio) of the fractionated lignin, as well as the total yield of benzoic acid compounds derived from the β-O-4 bond cleavage. This study elucidates the relationship between solvent properties and lignin structure and proposes a promising approach for refining lignin to enhance utilization efficiency, thereby presenting a potential strategy for value-added application of complex lignin polymers.

Impact of immediate release film coating on the disintegration process of tablets

Pharmaceutical tablets are often coated with a layer of polymeric material to protect the drug from environmental degradation, facilitate the packaging process, and enhance patient compliance. However, the detailed effects of such coating layers on drug release are not well understood. To investigate this, flat-faced pure microcrystalline cellulose tablets with a diameter of 13 mm and a thickness between 1.5 mm to 1.6 mm were directly compressed, and a film coating layer with a thickness of 80 μm to 120 μm was applied to one face of these tablets. This tablet geometry and immediate release film coating were chosen as a model system to understand how the film coating interacts with the tablet core. The coating hydration and dissolution process was studied using terahertz pulsed imaging, while optical coherence tomography was used to capture further details on the swelling process of the polymer in the coated tablet. The study investigated the film coating polymer dissolution process and found the gelling of dissolving polymer restricted the capillary liquid transport in the core. These findings can help predict the dissolution of film coating within the typical range of thickness (30 μm to 40 μm) and potentially be extended to understand modified release coating formulations.

Colloidal Templating in Catalyst Design for Thermocatalysis

Conventional catalyst preparative methods commonly entail the impregnation, precipitation, and/or immobilization of nanoparticles on their supports. While convenient, such methods do not readily afford the ability to control collective ensemble-like nanoparticle properties, such as nanoparticle proximity, placement, and compartmentalization. In this Perspective, we illustrate how incorporating colloidal templating into catalyst design for thermocatalysis confers synthetic advantages to facilitate new catalytic investigations and augment catalytic performance, focusing on three colloid-templated catalyst structures: 3D macroporous structures, hierarchical macro-mesoporous structures, and discrete hollow nanoreactors. We outline how colloidal templating decouples the nanoparticle and support formation steps to devise modular catalyst platforms that can be flexibly tuned at different length scales. Of particular interest is the raspberry colloid templating (RCT) method which confers high thermomechanical stability by partially embedding nanoparticles within its support, while retaining high levels of reactant accessibility. We illustrate how the high modularity of the RCT approach allows one to independently control collective nanoparticle properties, such as nanoparticle proximity and localization, without concomitant changes to other catalytic descriptors that would otherwise confound analyses of their catalytic performance. We next discuss how colloidal templating can be employed to achieve spatially disparate active site functionalization while directing reactant transport within the catalyst structure to enhance selectivity in multistep catalytic cascades. Throughout this Perspective, we highlight developments in advanced characterization that interrogate transport phenomena and/or derive new insights into these catalyst structures. Finally, we offer our outlook on the future roles, applications, and challenges of colloidal templating in catalyst design for thermocatalysis.

From Plastic Waste to Green Hydrogen and Valuable Chemicals Using Sunlight and Water

Over 79 % of 6.3 billion tonnes of plastics produced from 1950 to 2015 have been disposed in landfills or found their way to the oceans, where they will reside for up to hundreds of years before being decomposed bringing upon significant dangers to our health and ecosystems. Plastic photoreforming offers an appealing alternative by using solar energy and water to transform plastic waste into value-added chemical commodities, while simultaneously producing green hydrogen via the hydrogen evolution reaction. This review aims to provide an overview of the underlying principles of emerging plastic photoreforming technologies, highlight the challenges associated with experimental protocols and performance assessments, discuss recent global breakthroughs on the photoreforming of plastics, and propose perspectives for future research. A critical assessment of current plastic photoreforming studies shows a lack of standardised conditions, hindering comparison amongst photocatalyst performance. Guidelines to establish a more accurate evaluation of materials and systems are proposed, with the aim to facilitate the translation of promising fundamental discovery in photocatalysts design.

Effect of Physicochemical Properties on the Basic Drug-Acid-Polymer Interactions and Miscibility in PVA Based Orodispersible Films

Salts of weakly basic drugs can partially dissociate in formulations, to give basic drugs and counter acids. The aim of the present study was to clarify the effect of physicochemical properties on the basic drug-acid-polymer interactions and salt-polymer miscibility, and to explain the influence mechanism at the molecular level. Six maleate salts with different physicochemical properties were selected and PVA was used as the film forming material. The relationship between the physicochemical properties and the miscibility was presented with multiple linear regression analysis. The existence state of salts in formulations were determined by XRD and Raman imaging. The stability of salts was characterized by NMR and XPS. The intermolecular interactions were investigated by FTIR and NMR. The results showed that the salt-PVA miscibility was related to polar surface area of salts and Tg of free bases, which represented hydrogen bond interaction and solubility potential. The basic drug-acid-PVA intermolecular interactions determined the existence state and bonding pattern of the three molecules. Meanwhile, the decrease of the stability after formulation increased the number of free bases in orodispersible films, which in turn affected the miscibility with PVA. The study provided references for the rational design of PVA based orodispersible films.

Synthesis of Nanosized γ-Cyclodextrin Metal-Organic Frameworks as Carriers of Limonene for Fresh-Cut Fruit Preservation Based on Polycaprolactone Nanofibers

To address the issue of bacterial growth on fresh-cut fruits, this paper reports the synthesis of nanosized γ-cyclodextrin metal-organic frameworks (CD-MOFs) using an ultrasound-assisted method and their application as carriers of limonene for antibacterial active packaging. The effects of the processing parameters on the morphology and crystallinity of the CD-MOFs are investigated, and the results prove that the addition of methanol is the key to producing nanosized CD-MOFs. The limonene loading content of the nanosized CD-MOFs can reach approximately 170 mg g-1. The sustained-release behaviors of limonene in the CD-MOFs are evaluated. Molecular docking simulations reveal the distribution and binding sites of limonene in the CD-MOFs. CD-MOFs are deposited on the surfaces of polycaprolactone (PCL) nanofibers via an immersion method, and limonene-loaded CD-MOF@PCL nanofibers are prepared. The morphology, crystallinity, thermal stability, mechanical properties, and antibacterial activity of the nanofibers are also studied. The nanofiber film effectively inhibits bacterial growth and prolongs the shelf life of fresh-cut apples. This study provides a novel strategy for developing antibacterial active packaging materials based on CD-MOFs and PCL nanofibers.

Ethanol Solvation of Polymer Residues in Graphene Solution-Gated Field Effect Transistors

The persistence of photoresist residues from microfabrication procedures causes significant obstacles in the technological advancement of graphene-based electronic devices. These residues induce undesired chemical doping effects, diminish carrier mobility, and deteriorate the signal-to-noise ratio, making them critical in certain contexts, including sensing and electrical recording applications. In graphene solution-gated field-effect transistors (gSGFETs), the presence of polymer contaminants makes it difficult to perform precise electrical measurements, introducing response variability and calibration challenges. Given the absence of viable short to midterm alternatives to polymer-intensive microfabrication techniques, a postpatterning treatment involving THF and ethanol solvents was evaluated, with ethanol being the most effective, environmentally sustainable, and safe method for residue removal. Employing a comprehensive analysis with XPS, AFM, and Raman spectroscopy, together with electrical characterization, we investigated the influence of residual polymers on graphene surface properties and transistor functionality. Ethanol treatment exhibited a pronounced enhancement in gSGFET performance, as evidenced by a shift in the charge neutrality point and reduced dispersion. This systematic cleaning methodology holds the potential to improve the reproducibility and precision in the manufacturing of graphene devices. Particularly, by using ethanol for residue removal, we align our methodology with the principles of green chemistry, minimizing environmental impact while advancing diverse graphene technology applications.

Nile red staining for rapid screening of plastic-suspect particles in edible seafood tissues

Concerns regarding microplastic (MP) contamination in aquatic ecosystems and its impact on seafood require a better understanding of human dietary MP exposure including extensive monitoring. While conventional techniques for MP analysis like infrared or Raman microspectroscopy provide detailed particle information, they are limited by low sample throughput, particularly when dealing with high particle numbers in seafood due to matrix-related residues. Consequently, more rapid techniques need to be developed to meet the requirements of large-scale monitoring. This study focused on semi-automated fluorescence imaging analysis after Nile red staining for rapid MP screening in seafood. By implementing RGB-based fluorescence threshold values, the need for high operator expertise to prevent misclassification was addressed. Food-relevant MP was identified with over 95% probability and differentiated from natural polymers with a 1% error rate. Comparison with laser direct infrared imaging (LDIR), a state-of-the-art method for rapid MP analysis, showed similar particle counts, indicating plausible results. However, highly variable recovery rates attributed to inhomogeneous particle spiking experiments highlight the need for future development of certified reference material including sample preparation. The proposed method demonstrated suitability of high throughput analysis for seafood samples, requiring 0.02-0.06 h/cm2 filter surface compared to 4.5-14.7 h/cm with LDIR analysis. Overall, the method holds promise as a screening tool for more accurate yet resource-intensive MP analysis methods such as spectroscopic or thermoanalytical techniques.

Efficient Alcoholysis of Poly(ethylene terephthalate) by Using Supercritical Carbon Dioxide as a Green Solvent

In order to reduce the environmental impact of poly(ethylene terephthalate) (PET) plastic waste, supercritical fluids were used to facilitate effective recovery via improved solvent effects. This work focuses on the mechanisms of supercritical CO2 (ScCO2) during the alcoholysis processing of PET using systematic experiments and molecular dynamics (MD) simulations. The results of the alcoholysis experiment indicated that PET chips can be completely depolymerized within only an hour at 473 K assisted with ScCO2 at an optimal molar ratio of CO2/ethanol of 0.2. Random scission of PET dominates the early stage of the depolymerization reaction process, while specific scission dominates the following stage. Correspondingly, molecular dynamics (MD) simulations revealed that the solubilization and self-diffusion properties of ScCO2 facilitate the transportation of alcohol molecules into the bulk phase of PET, which leads to an accelerated diffusion of both oligomers and small molecules in the system. However, the presence of excessive CO2 has a negative impact on depolymerization by weakening the hydrogen bonding between polyester chain segments and ethanol, as well as decreasing the swelling degree of PET. These data provide a deep understanding of PET degradation by alcohols and the enhancement of ScCO2. It should be expected to achieve an efficient and high-yield depolymerization process of wasted polyesters assisted with ScCO2 at a relatively low temperature.

Fabrication of Polypyrrole Hollow Nanospheres by Hard-Template Method for Supercapacitor Electrode Material

Conducting polymers like polypyrrole, polyaniline, and polythiophene with nanostructures offers several advantages, such as high conductivity, a conjugated structure, and a large surface area, making them highly desirable for energy storage applications. However, the direct synthesis of conducting polymers with nanostructures poses a challenge. In this study, we employed a hard template method to fabricate polystyrene@polypyrrole (PS@PPy) core-shell nanoparticles. It is important to note that PS itself is a nonconductive material that hinders electron and ion transport, compromising the desired electrochemical properties. To overcome this limitation, the PS cores were removed using organic solvents to create hollow PPy nanospheres. We investigated six different organic solvents (cyclohexane, toluene, tetrahydrofuran, chloroform, acetone, and N,N-dimethylformamide (DMF)) for etching the PS cores. The resulting hollow PPy nanospheres showed various nanostructures, including intact, hollow, buckling, and collapsed structures, depending on the thickness of the PPy shell and the organic solvent used. PPy nanospheres synthesized with DMF demonstrated superior electrochemical properties compared to those prepared with other solvents, attributed to their highly effective PS removal efficiency, increased specific surface area, and improved charge transport efficiency. The specific capacitances of PPy nanospheres treated with DMF were as high as 350 F/g at 1 A/g. And the corresponding symmetric supercapacitor demonstrated a maximum energy density of 40 Wh/kg at a power density of 490 W/kg. These findings provide new insights into the synthesis method and energy storage mechanisms of PPy nanoparticles.

Tailoring the Properties of Gel Polymer Electrolytes for Sodium-Ion Batteries Using Ionic Liquids: A Review

Ionic liquids are an extraordinary group of compounds, fully ionic in structure like inorganic salts but with low melting points, that resemble organic molecular solvents. Their chemical, electrochemical, and thermal stability is what draws the attention and enables their use in many applications, including electrochemical power sources. Even though they are no longer considered eco-friendly because of nonnegligible toxicity and long bioaccumulation, they can still be efficiently recovered, purified, and reused. These attributes can be harvested to enhance the properties of gel polymer electrolytes for the emerging sodium-ion batteries. The variety of anions and cations for ILs and their influence on the final properties of the compound opens the road to tuning the properties of gel polymer electrolytes. Ionic liquids as plasticizers constitute a major part of gel polymer electrolytes (average of 70 wt%) and hence, they affect the fundamental properties of gel electrolytes like ionic conductivity and electrochemical window. They also improve the safety features of sodium-ion batteries, which is relevant for their anticipated applications in stationary energy storage and electric vehicles. The presented review paper aims to explain the relationship between the cation and anion in ionic liquid and the properties of gel electrolytes for sodium-ion batteries.

Clean Transfer of Two-Dimensional Materials: A Comprehensive Review

The growth of two-dimensional (2D) materials through chemical vapor deposition (CVD) has sparked a growing interest among both the industrial and academic communities. The interest stems from several key advantages associated with CVD, including high yield, high quality, and high tunability. In order to harness the application potentials of 2D materials, it is often necessary to transfer them from their growth substrates to their desired target substrates. However, conventional transfer methods introduce contamination that can adversely affect the quality and properties of the transferred 2D materials, thus limiting their overall application performance. This review presents a comprehensive summary of the current clean transfer methods for 2D materials with a specific focus on the understanding of interaction between supporting layers and 2D materials. The review encompasses various aspects, including clean transfer methods, post-transfer cleaning techniques, and cleanliness assessment. Furthermore, it analyzes and compares the advances and limitations of these clean transfer techniques. Finally, the review highlights the primary challenges associated with current clean transfer methods and provides an outlook on future prospects.

Lignin derived hydrophobic deep eutectic solvents for the extraction of nanoplastics from water

As a growing concern in aqueous systems, micro- and nano-plastics, especially nanoplastics (NPs), have been widely detected in the environment and organisms, posing a potential threat to ecosystems and human health. Hydrophobic deep eutectic solvents (HDESs) have emerged as environmentally friendly solvents that have shown promise for extracting pollutants from water, either for detection or removal purposes. Herein, we investigated the extraction of polystyrene (PS) and polyethylene terephthalate (PET) NPs from aqueous solution using lignin based HDESs as sustainable solvents. Rapid extraction of both PET and PS NPs was observed with the high extraction efficiency achieved (> 95%). The extraction capacities for PET and PS could reach up to 525.877 mg/mL and 183.520 mg/mL, respectively, by the Thymol-2,6-dimethoxyphenol 1:2 HDES. Moreover, the extraction mechanism was studied using various techniques including Fourier-transform infrared analysis, contact angle measurements, molecular dynamics simulation, kinetics, and isotherm studies. This work lays a foundational basis for the future development of innovative HDES-based technologies in the detection and remediation of NPs as part of the grand challenge of plastic pollution.

Innovative hydrothermal technique in efficient disengagement of waste solar panels

The delamination of layers of waste solar panels remains a major challenge due to the lack of effective solutions for removing the adhesive between layers. In this study, a novel efficient method for disengagement of glass from the rest of the module is introduced, in which only water is used under high pressure (<3 MPa) and relatively low temperatures (230-250 °C) in a hydrothermal reactor, allowing for facile separation of the glass from the interlayer. The other layers of the module can also easily be peeled apart in subsequent processes. The separated glass is free of metals and polymers that can be utilized directly for further applications. The benefits of this method include no use of chemicals, preservation of the recovered materials' quality (i.e., interlayers, Si sheet, and glass), relatively low-temperature operation, no hazardous gas generation, and reduced energy consumption. A pilot scale design of the method has been proposed for processing a full panel, demonstrating its industrial viability.

Hard Candy Production and Quality Parameters: A review

Hard candies are sugar confections comprising mainly water and sucrose. Corn syrup, colorants and flavors are also usually added to hard candy formulations. The production of hard candy requires heating of the ingredients to very high temperatures to reduce moisture content and subsequent cooling to obtain a solid matrix. Cooling of the mixtures achieves the final, well known glassy state of the products. In this glassy state, the system is kinetically stable and molecular mobility is restricted, providing longer shelf life to hard candies. There are, however, several factors affecting the final quality and consumer acceptance of hard candies. Production methods and parameters, initial formulations as well as storage conditions all play a crucial role in the physicochemical, textural and sensory properties of hard candies. Addition of colorants and flavors also plays a vital role in the final quality. Although hard candy production is a simple process with few production stages, even small changes in the method of production and process parameters may induce substantial changes in the final product characteristics. Additionally, storage conditions such as temperature and humidity can change the product properties leading to graining and stickiness which are the two major problems for hard candies during storage. Both production and storage conditions should therefore be carefully chosen and controlled for desirable hard candy properties. This review addresses the general production methods and considers process parameters and quality parameters of hard candy products. Moreover, a comprehensive review of the related hard candy literature is also presented. The majority of hard candy reviews focus on specific methods and processes, but this review will present a more general frame on the subject.

Selective Vapor Condensation for the Synthesis and Assembly of Spherical Colloids with a Precise Rough Patch

Patchy particles occupy an increasingly important space in soft matter research due to their ability to assemble into intricate phases and states. Being able to fine-tune the interactions among these particles is essential to understanding the principles governing the self-assembly processes. However, current fabrication techniques often yield patches that deviate chemically and physically from the native particles, impeding the identification of the driving forces behind self-assembly. To overcome this challenge, we propose a new approach to synthesizing spherical colloids with a well-defined rough patch on their surface. By treating polystyrene microspheres with vapors of a good solvent, here an acetone-water mixture, we achieve selective polymer corrugation on the particle surface resulting in a chemically similar yet rough surface patch. The key step is the selective condensation of the acetone-water vapors on the apex of the polystyrene microparticles immobilized on a substrate, which leads to rough patch formation. We leverage the ability to tune the vapor-liquid equilibrium of the volatile acetone-water mixture to precisely control the polymer corrugation on the particle surface. We demonstrate the dependence of patch formation on particle and substrate wettability, with the condensation occurring on the particle apex only when it is more wettable than the substrate, which is consistent with Volmer's classical nucleation theory. By combining experiments and molecular dynamics simulations, we identify the role of the rough patch in the depletion interaction-driven self-assembly of the microspheres, which is crucial for designing programmable supracolloidal structures.

Increasing the Dissolution Rate of Polystyrene Waste in Solvent-Based Recycling

Solvent-based recycling of plastic waste is a promising approach for cleaning polymer chains without breaking them. However, the time required to actually dissolve the polymer in a lab environment can take hours. Different factors play a role in polymer dissolution, including temperature, turbulence, and solvent properties. This work provides insights into bottlenecks and opportunities to increase the dissolution rate of polystyrene in solvents. The paper starts with a broad solvent screening in which the dissolution times are compared. Based on the experimental results, a multiple regression model is constructed, which shows that within several solvent properties, the viscosity of the solvent is the major contributor to the dissolution time, followed by the hydrogen, polar, and dispersion bonding (solubility) parameters. These results also indicate that cyclohexene, 2-pentanone, ethylbenzene, and methyl ethyl ketone are solvents that allow fast dissolution. Next, the dissolution kinetics of polystyrene in cyclohexene in a lab-scale reactor and a baffled reactor are investigated. The effects of temperature, particle size, impeller speed, and impeller type were studied. The results show that increased turbulence in a baffled reactor can decrease the dissolution time from 40 to 7 min compared to a lab-scale reactor, indicating the importance of a proper reactor design. The application of a first-order kinetic model confirms that dissolution in a baffled reactor is at least 5-fold faster than that in a lab-scale reactor. Finally, the dissolution kinetics of a real waste sample reveal that, in optimized conditions, full dissolution occurs after 5 min.

Manipulation of Cationic Group Density in Covalent Organic Framework Membranes for Efficient Anion Transport

Anion exchange membranes with high anion conductivity are highly desired for electrochemical applications. Increasing ion exchange capacity is a straightforward approach to enhancing anion conductivity but faces a challenge in dimensional stability. Herein, we report the design and preparation of three kinds of isoreticular covalent organic framework (COF) membranes bearing tunable quaternary ammonium group densities as anion conductors. Therein, the cationic groups are integrated into the backbones by flexible ether-bonded alkyl side chains. The highly quaternary ammonium-group-functionalized building units endow COF membranes with abundant cationic groups homogeneously distributed in the ordered channels. The flexible side chains alleviate electrostatic repulsion and steric hindrance caused by large cationic groups, ensuring a tight interlayer stacking and multiple interactions. As a result, our COF membranes achieve a high ion exchange capacity and exceptional dimensional stability simultaneously. Furthermore, the effect of the ionic group density on the ion conductivity in rigid COF channels is systematically explored. Experiments and simulations reveal that the ionic group concentration and side chain mobility jointly determine the ion transport behavior, resulting in the abnormal phenomenon that the anion conductivity is not positively correlated to the ionic group density. The optimal COF membrane achieves the ever-reported highest hydroxide ion conductivity over 300 mS cm-1 at 80 °C and 100% RH. This study offers insightful guidelines on the rational design and preparation of high-performance anion conductors.

CO2-Responsive Low Molecular Weight Polymer with High Osmotic Pressure as a Draw Solute for Forward Osmosis

A key challenge in the development of forward osmosis (FO) technology is to identify a suitable draw solute that can generate a large osmotic pressure with favorable water flux while being easy to recover after the FO process with a minimum of energy expenditure. While the CO2- and thermo-responsive linear poly(N,N-dimethylallylamine) polymer (l-PDMAAm) has been reported as a promising draw agent for forward osmosis desalination, the draw solutions sufficiently concentrated to have high osmotic pressure were too viscous to be usable in industrial operations. We now compare the viscosities and osmotic pressures of solutions of these polymers at low and high molecular weights and with/without branching. The best combination of high osmotic pressures with low viscosity can be obtained by using low molecular weights rather than branching. Aqueous solutions of the synthesized polymer showed a high osmotic pressure of 170 bar under CO2 (πCO2) at 50 wt% loading, generating a high water flux against NaCl feed solutions in the FO process. Under air, however, the same polymer showed a low osmotic pressure and a cloud point between 26 and 33 °C (depending on concentration), which facilitates the recovery of the polymer after it has been used as a draw agent in the FO process upon removal of CO2 from the system.

Solvent-activated 3D-printed electrodes and their electroanalytical potential

This work is a comprehensive study describing the optimization of the solvent-activated carbon-based 3D printed electrodes. Three different conductive filaments were used for the preparation of 3D-printed electrodes. Electrodes treatment with organic solvents, electrochemical characterization, and finally electroanalytical application was performed in a dedicated polyamide-based cell also created using 3D printing. We have investigated the effect of the used solvent (acetone, dichloromethane, dichloroethane, acetonitrile, and tetrahydrofuran), time of activation (from immersion up to 3600 s), and the type of commercially available filament (three different options were studied, each being a formulation of a polylactic acid and conductive carbon material). We have obtained and analysed a significant amount of collected data which cover the solvent-activated carbon-based electrodes surface wettability, microscopic insights into the surface topography analysed with scanning electron microscopy and atomic force microscopy, and finally voltammetric evaluation of the obtained carbon electrodes electrochemical response. All data are tabulated, discussed, and compared to finally provide the superior activation procedure. The electroanalytical performance of the chosen electrode is discussed based on the voltammetric detection of ferrocenemethanol.

Characterizing lignins from various sources and treatment processes after optimized sample preparation techniques and analysis via ESI-HRMS and custom mass defect software tools

Sample preparation of complex, natural mixtures such as lignin prior to mass spectrometry analysis, however minimal, is a critical step in ensuring accurate and interference-free results. Modern shotgun-MS techniques, where samples are directly injected into a high-resolution mass spectrometer (HRMS) with no prior separation, usually still require basic sample pretreatment such as filtration and appropriate solvents for full dissolution and compatibility with atmospheric pressure ionization interfaces. In this study, sample preparation protocols have been established for a unique sample set consisting of a wide variety of degraded lignin samples from numerous sources and treatment processes. The samples were analyzed via electrospray (ESI)-HRMS in negative and positive ionization modes. The resulting information-rich HRMS datasets were then transformed into the mass defect space with custom R scripts as well as the open-source Constellation software as an effective way to visualize changes between the samples due to the sample preparation and ionization conditions as well as a starting point for comprehensive characterization of these varied sample sets. Optimized conditions for the four investigated lignins are proposed for ESI-HRMS analysis for the first time, giving an excellent starting point for future studies seeking to better characterize and understand these complex mixtures.

Effect of Aprotic Solvents on the Microtensile Bond Strength of Composite Core and Fiber-Reinforced Composite Posts

This investigation evaluated the effects of aprotic solvents, i.e., tetrahydrofuran, pyridine, and morpholine, compared with hydrogen peroxide, on the surfaces of fiber-reinforced composite posts with a composite core based on the microtensile bond strength. In total, 150 FRC Postec Plus posts and 150 D.T. Light-Posts were randomly divided into three groups (non-thermocycling, 5000-cycle, and 10,000-cycle thermocycling groups). Each group was divided into five subgroups according to the post-surface treatment: C, non-treatment group; H2O2, immersed in 35% hydrogen peroxide; THF, immersed in tetrahydrofuran; PY, immersed in pyridine; and MP, immersed in morpholine. The treated specimens were placed in the bottom of a plastic cap and filled with a composite core material in preparation for the microtensile bond test. The data were evaluated using one-way ANOVA and Tukey's test (p < 0.05) as well as an independent t-test (p < 0.05). For the surface roughness, white light interferometry was used for measurement, and the mean surface roughness was analyzed via one-way ANOVA and Tukey's test (p < 0.05). The results showed that, under non-thermocycling conditions, the PY subgroup with D.T. Light-Post had the highest microtensile bond strength, followed by THF, MP, H2O2, and the control groups. For FRC Postec Plus, the PY group had the highest microtensile bond strength, followed by MP, THF, H2O2, and the control groups. Although the thermocycling conditions decreased the microtensile bond strength in all groups, the PY subgroup still had the highest value. An independent t-test revealed that even under all non-thermocycling and 5000- and 10,000-cycle thermocycling conditions, D.T. Light-Post in the PY subgroup displayed significantly higher microtensile bond strengths than FRC Postec Plus in the PY subgroup. While the surface roughness of the fiber-reinforced composite posts showed that the posts treated with pyridine possessed the highest surface roughness for each material type, In conclusion, as an aprotic solvent, pyridine generates the highest microtensile bond strength between the interfaces of composite cores and fiber-reinforced composite posts.

Understanding the complexity of deinking plastic waste: An assessment of the efficiency of different treatments to remove ink resins from printed plastic film

Plastic packaging is usually heavily printed with inks to provide functional benefits. However, the presence of inks strongly impedes the closed-loop recycling of plastic films. Various media have already been studied for the deinking of plastic films, but there is little scientific insight into the effectiveness of different deinking techniques. Therefore, this study aims to obtain a systematic understanding by measuring the liquefaction and maximum solubility of 14 chemically different polymer resins in seven different media typically used in plastic deinking, such as acetone, ethyl acetate, sodium hydroxide solution, cetyltrimethylammonium bromide solution, formic acid, sulfuric acid, and N,N-dimethylcyclohexylamine. Our findings show that acid-based media are able to remove a broader range of polymer resins. Organic solvents are particularly effective against acrylics and related polymer resins. The deinking efficiency tests on pure resins are also confirmed by deinking four printed plastic films containing different classes of polymer resins. A basic cost and environmental impact analysis is given to evaluate scale-up potential of the deinking medium.

Mesoscale Simulations of Structure Formation in Polyacrylonitrile Nascent Fibers Induced by Binary Solvent Mixture

Polyacrylonitrile (PAN) is widely used as a raw material for the production of high-modulus carbon fibers, the internal structure of which is directly affected by the spinning of the precursor. Although PAN fibers have been studied for a long time, the formation of their internal structure has not been sufficiently investigated theoretically. This is due to the large number of stages in the process and the parameters controlling them. In this study, we present a mesoscale model describing the evolution of nascent PAN fibers during the coagulation. It is constructed within the framework of a mesoscale dynamic density functional theory. We use the model to study the influence of a combined solvent of dimethyl sulfoxide (DMSO, a good solvent) and water (a non-solvent) on the microstructure of the fibers. A porous structure of PAN is formed as a result of the microphase separation of the polymer and the residual combined solvent at a high water content in the system. The model shows that one of the possible ways to obtain the homogeneous fiber structure is to slow down the coagulation by increasing the amount of good solvent in the system. This result is in agreement with the existing experimental data and confirms the efficiency of the presented model.

Removal of polyvinylidene fluoride binder and other organics for enhancing the leaching efficiency of lithium and cobalt from black mass

The agglomeration and encapsulation of recoverable materials of interest (e.g. metals and graphite) as a result of the presence of polyvinylidene fluoride (PVDF) in spent lithium-ion batteries (LIBs) with mixed chemistries (black mass) lower the extraction efficiency of metals. In this study, organic solvents and alkaline solutions were used as non-toxic reagents to investigate the removal of a PVDF binder from a black mass. The results demonstrated that 33.1%, 31.4%, and 31.4% of the PVDF were removed using dimethylformamide (DMF), dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO) at 150, 160, and 180 °C, respectively. Under these conditions, the peel-off efficiencies for DMF, DMAc, and DMSO were 92.9%, 85.3%, and approximately 92.9%, respectively. Using tetrabutylammonium bromide (TBAB) as a catalyst and 5 M sodium hydroxide (NaOH) at room temperature (RT- 21 °C-23 °C), 50.3% of PVDF and other organic compounds were eliminated. The removal efficiency was enhanced to approximately 60.5% when the temperature was raised to 80 °C using NaOH. Using 5 M potassium hydroxide at RT in a TBAB-containing solution, ca. 32.8% removal efficiency was obtained; raising the temperature to 80 °C further enhanced the removal efficiency to almost 52.7%. The peel-off efficiency was 100% for both alkaline solutions. Lithium extraction increased from 47.2% to 78.7% following treatment with DMSO and to 90.1% following treatment with NaOH via leaching black mass (2 M sulfuric acid, solid-to-liquid ratio (S/L): 100 g L-1 at 50 °C, for 1 h without a reducing agent) before and after removal of the PVDF binder. Cobalt's recovery went from 28.5% to 61.3% with DMSO treatment to 74.4% with NaOH treatment.

Fast Fabrication of Porous Amphiphilic Polyamides via Nonconventional Evaporation Induced Phase Separation

In the present work, we report a facile approach for the fast fabrication of porous films and coatings of long-chain polyamides through a nonconventional evaporation induced phase separation. Because of its amphiphilic nature, polyamide 12 can be dissolved in the mixture of a high-polarity solvent and a low-polarity solvent, while it could not be dissolved in either solvent solely. The sequential and fast evaporation of the solvents leads to the formation of porous structures within 1 min. Moreover, we have investigated the dependence of the pore structures on composition of the solutions, and have demonstrated that our approach can be applied to other long-chain polycondensates, too. Our findings can provide insight on the fabrication of porous materials by using amphiphilic polymers.

Recent Advances in the Incorporation of Polysaccharides with Antioxidant and Antibacterial Functions to Preserve the Quality and Shelf Life of Meat Products

Meat and meat products are susceptible to various types of natural processes such as oxidative degradation due to their high content of protein and essential amino acids. However, finding solutions to maintain the nutritional and sensory quality of meat and meat products is unavoidable. Hence, there is a pressing need to investigate alternatives to synthetic preservatives, focusing on active biomolecules of natural provenance. Polysaccharides are natural polymers of various sources that exhibit antibacterial and antioxidant properties via a variety of mechanisms, owing to their diversity and structural variation. For this reason, these biomolecules are widely studied in order to improve texture, inhibit the growth of pathogens, and improve the oxidative stability and sensory characteristics of meat products. However, the literature has not addressed their biological activity in meat and meat products. This review summarizes the various sources of polysaccharides, their antioxidant and antibacterial activities (mainly against pathogenic food strains), and their use as natural preservatives to replace synthetic additives in meat and meat products. Special attention is given to the use of polysaccharides to improve the nutritional value of meat, resulting in more nutrient-rich meat products with higher polysaccharide content and less salt, nitrites/nitrates, and cholesterol.

Dissolution Mechanisms of Amorphous Solid Dispersions: A Close Look at the Dissolution Interface

Despite the recent success of amorphous solid dispersions (ASDs) at enabling the delivery of poorly soluble small molecule drugs, ASD-based dosage forms are limited by low drug loading. This is partially due to a sharp decline in drug release from the ASD at drug loadings surpassing the 'limit of congruency' (LoC). In some cases, the LoC is as low as 5% drug loading, significantly increasing the risk of pill burden. Despite efforts to understand the mechanism responsible for the LoC, a clear picture of the molecular processes occurring at the ASD/solution interface remains elusive. In this study, the ASD/solution interface was studied for two model compounds formulated as ASDs with copovidone. The evolution of a gel layer and its phase behavior was captured in situ with fluorescence confocal microscopy, where fluorescent probes were added to label the hydrophobic and hydrophilic phases. Phase separation was detected in the gel layer for most of the ASDs. The morphology of the hydrophobic phase was found to correlate with the release behavior, where a discrete phase resulted in good release and a continuous phase formed a barrier leading to poor release. The continuous phase formed at a lower drug loading for the system with stronger drug-polymer interactions. This was due to incorporation of the polymer into the hydrophobic phase. The study highlights the complex molecular and phase behavior at the ASD/solution interface of copovidone-based ASDs and provides a thermodynamic argument for qualitatively predicting the release behavior based on drug-polymer interactions.

Laser microdissection pressure catapulting (LMPC): a new technique to handle single microplastic particles for number-based validation strategies

This study examines laser microdissection pressure catapulting (LMPC) as an innovative method for microplastic research. Laser pressure catapulting as part of commercially available LMPC microscopes enables the precise handling of microplastic particles without any mechanical contact. In fact, individual particles with sizes between several micrometers and several hundred micrometers can be transported over centimeter-wide distances into a collection vial. Therefore, the technology enables the exact handling of defined numbers of small microplastics (or even individual ones) with the greatest precision. Herewith, it allows the production of particle number-based spike suspensions for method validation. Proof-of-principle LMPC experiments with polyethylene and polyethylene terephthalate model particles in the size range from 20 to 63 µm and polystyrene microspheres (10 µm diameter) demonstrated precise particle handling without fragmentation. Furthermore, the ablated particles showed no evidence of chemical alteration as seen in the particles' IR spectra acquired via laser direct infrared analysis. We propose LMPC as a promising new tool to produce future microplastic reference materials such as particle-number spiked suspensions, since LMPC circumvents the uncertainties resulting from the potentially heterogeneous behavior or inappropriate sampling from microplastic suspensions. Furthermore, LMPC could be advantageous for the generation of very accurate calibration series of spherical particles for microplastic analysis via pyrolysis-gas chromatography-mass spectrometry (down to 0.54 ng), as it omits the dissolution of bulk polymers.

Deformation constraints of graphene oxide nanochannels under reverse osmosis

Nanochannels in laminated graphene oxide nanosheets featuring confined mass transport have attracted interest in multiple research fields. The use of nanochannels for reverse osmosis is a prospect for developing next-generation synthetic water-treatment membranes. The robustness of nanochannels under high-pressure conditions is vital for effectively separating water and ions with sub-nanometer precision. Although several strategies have been developed to address this issue, the inconsistent response of nanochannels to external conditions used in membrane processes has rarely been investigated. In this study, we develop a robust interlayer channel by balancing the associated chemistry and confinement stability to exclude salt solutes. We build a series of membrane nanochannels with similar physical dimensions but different channel functionalities and reveal their divergent deformation behaviors under different conditions. The deformation constraint effectively endows the nanochannel with rapid deformation recovery and excellent ion exclusion performance under variable pressure conditions. This study can help understand the deformation behavior of two-dimensional nanochannels in pressure-driven membrane processes and develop strategies for the corresponding deformation constraints regarding the pore wall and interior.

Highly Efficient Production of Nanoporous Block Copolymers with Arbitrary Structural Characteristics for Advanced Membranes

The great significance of boosting the design of percolating nanopore structures in block copolymers (BCPs) for various cases has been widely demonstrated in the past several decades. However, it still remains challenging to prepare the desired porous structures in a rapid, facile, and universal manner. Here we have developed an unconventional and benchtop strategy to rapidly generate the nanoporous polystyrene-based BCPs with arbitrary structural characteristics regardless of the BCP bulk morphology. This universal pore-forming strategy enables the sustainable CO2 -based BCPs to form advanced membranes after 1 s soaking for efficiently rejecting 94.2 % brilliant blue R (826 g mol-1 ). Meanwhile, the water permeance retains around 1020 L (m2  h bar)-1 , which is 1-3 orders of magnitude higher than that of other membranes. This strategy may offer an excellent opportunity to introduce percolating pore structures in those newly developed BCPs with which the previously reported pore-forming methods may not deal.

Eudraguard® Natural and Protect: New "Food Grade" Matrices for the Delivery of an Extract from Sorbus domestica L. Leaves Active on the α-Glucosidase Enzyme

(1) Background: Eudraguard^® Natural (EN) and Protect (EP) are polymers regulated for use in dietary supplements in the European Union and the United States to carry natural products, mask unpleasant smells and tastes, ameliorate product handling, and protect products from moisture, light, and oxidation. Moreover, EN and EP can control the release of encapsulated compounds. The aim of this work was the development, preparation, and control of Eudraguard^® spray-drying microparticles to obtain powders with easy handling and a stable dietary supplement containing a polar functional extract (SOE) from Sorbus domestica L. leaves. (2) Methods: SOE was characterized using HPLC, NMR, FTIR, DSC, and SEM methods. Furthermore, the SOE's antioxidant/free radical scavenging activity, α-glucosidase inhibition, MTT assay effect on viability in normal cells, and shelf life were evaluated in both the extract and final formulations. (3) Results: The data suggested that SOE, rich in flavonoids, is a bioactive and safe extract; however, from a technological point of view, it was sticky, difficult to handle, and had low aqueous solubility. Despite the fact that EN and EP may undergo changes with spray-drying, they effectively produced easy-to-handle micro-powders with a controlled release profile. Although EN had a weaker capability to coat SOE than EP, EN acted as a substrate that was able to swell, drawing in water and improving the extract solubility and dissolution/release; however, EP was also able to carry the extract and provide SOE with controlled release. (4) Conclusion: Both Eudraguard^® products were capable of carrying SOE and improving its antioxidant and α-glucosidase inhibition activities, as well as the extract stability and handling.

Improving the Separation Properties of Polybenzimidazole Membranes by Adding Acetonitrile for Organic Solvent Nanofiltration

In research on membranes, the addition of co-solvents to the polymer dope solution is a common method for tuning the morphology and separation performance. For organic solvent nanofiltration (OSN) applications, we synthesized polybenzimidazole (PBI) membranes with high separation properties and stability by adding acetonitrile (MeCN) to the dope solution, followed by crosslinking with dibromo-p-xylene. Accordingly, changes in the membrane structure and separation properties were investigated when MeCN was added. PBI/MeCN membranes with a dense and thick active layer and narrow finger-like macrovoids exhibited superior rejection properties in the ethanol solution compared with the pristine PBI membrane. After crosslinking, they displayed superior rejection properties (96.56% rejection of 366-g/mol polypropylene glycol). In addition, the membranes demonstrated stable permeances for various organic solvents, including acetone, methanol, ethanol, toluene, and isopropyl alcohol. Furthermore, to evaluate the feasibility of the modified PBI OSN membranes, ecamsule, a chemical product in the fine chemical industry, was recovered. Correspondingly, the efficient recovery of ecamsule from a toluene/methanol solution using the OSN process with PBI/MeCN membranes demonstrated their applicability in many fine chemical industries.

Dissolution Mechanisms of Amorphous Solid Dispersions: Role of Drug Load and Molecular Interactions

High drug load amorphous solid dispersions (ASDs) have been a challenge to formulate partially because drug release is inhibited at high drug loads. The maximum drug load prior to inhibition of release has been termed the limit of congruency (LoC) and has been most widely studied for copovidone (PVPVA)-based ASDs. The terminology was derived from the observation that below LoC, the polymer controlled the kinetics and the drug and the polymer released congruently, while above LoC, the release rates diverged and were impaired. Recent studies show a correlation between the LoC value and drug-polymer interaction strength, where a lower LoC was observed for systems with stronger interactions. The aim of this study was to investigate the causality between drug-PVPVA interaction strength and LoC. Four chemical analogues with diverse abilities to interact with PVPVA were used as model drugs. The distribution of the polymer between the dilute aqueous phase and the insoluble nanoparticles containing drug was studied with solution nuclear magnetic resonance spectroscopy and traditional separation techniques to understand the thermodynamics of the systems in a dilute environment. Polymer diffusion to and from ASD particles suspended in aqueous solution was monitored for drug loads above the LoC to investigate the thermodynamic driving force for polymer release. The surface composition of ASD compacts before and after exposure to buffer was studied with Fourier transform infrared spectroscopy to capture potential kinetic barriers to release. It was found that ASD compacts with drug loads above the LoC formed an insoluble barrier on the surface that was in pseudo-equilibrium with the aqueous phase and prevented further release of drugs and polymers during dissolution. The insoluble barrier contained a substantial amount of the polymer for the strongly interacting drug-polymer systems. In contrast, a negligible amount was found for the weakly interacting systems. This observation provides an explanation for the ability of strongly interacting systems to form an insoluble barrier at lower drug loads. The study highlights the importance of thermodynamic and kinetic factors on the dissolution behavior of ASDs and provides a potential framework for maximizing the drug load in ASDs.

Release Mechanisms of Amorphous Solid Dispersions: Role of Drug-Polymer Phase Separation and Morphology

Formulating poorly soluble molecules as amorphous solid dispersions (ASDs) is an effective strategy to improve drug release. However, drug release rate and extent tend to rapidly diminish with increasing drug loading (DL). The poor release at high DLs has been postulated to be linked to the process of amorphous-amorphous phase separation (AAPS), although the exact connection between phase separation and release properties remains somewhat unclear. Herein, release profiles of ASDs formulated with ritonavir (RTV) and polyvinylpyrrolidone/vinyl acetate (PVPVA) at different DLs were determined using surface normalized dissolution. Surface morphologies of partially dissolved ASD compacts were evaluated with confocal fluorescence microscopy, using Nile red and Alexa Fluor 488 as fluorescence markers to track the hydrophobic and hydrophilic phases respectively. ASD phase behavior during hydration and release of components were also visualized in real time using a newly developed in situ confocal fluorescence microscopy method. RTV-PVPVA ASDs showed complete and rapid drug release below 30% DL, partial drug release at 30% DL and no drug release above 30% DL. It was observed that formation of discrete drug-rich droplets at lower DLs led to rapid and congruent release of both drug and polymer, whereas formation of continuous drug-rich phase at the ASD matrix-solution interface was the cause of poor release above certain DLs. Thus, the domain size and interconnectivity of phase separated drug-rich domains appear to be critical factors impacting drug release from RTV-PVPVPA ASDs.

A colorimetric detection of polystyrene nanoplastics with gold nanoparticles in the aqueous phase

Nanoplastics has become a growing environmental concern because these tiny particles can easily penetrate biological tissues and have possible toxic effects. FT-IR and Raman spectroscopy methods are currently used to analyze microplastics (5 mm or less), but they encounter difficulty when the particles are below 1 μm. On the other hand, thermoanalysis of nanoplastics does not provide the size information. Therefore, herein, we proposed the colorimetric detection method with gold nanoparticles (AuNPs) to measure the concentration of polystyrene nanoplastics (PSNPs, size = 350 and 880 nm) through a color change that is obvious to the naked eye. A mixed dispersion of PSNPs and AuNPs was added with acetone, a good solvent for polystyrene. In this colorimetric detection, acetone acted as a key component to enhance or hinder the aggregation of AuNPs around PSNPs. Namely, acetone itself promoted AuNPs aggregation, but it was dissolved partially PS chains from PSNSs to act as inhibitor of aggregation of AuNPs. These two contradictory feature of acetone to AuNPs and PSNPs affect the aggregation and color of AuNPs (dispersed = red, aggregated = blue). Finally, the heat-map between PSNSs and acetone was prepared to use for estimation of concentration of PSNPs in the aqueous solution with naked eye. To the best of our knowledge, this is the first attempt to measure nanoplastics by colorimetry.

Selection of Conditions in PVB Polymer Dissolution Process for Laminated Glass Recycling Applications

Polyvinyl(butyral) (PVB) post-production waste collected from the windshields of end-of-life vehicles and post-consumer building laminated glass are valuable polymeric materials that can be reused. Every year, large amounts of PVB waste are still being buried in landfills owing to a lack of appropriate recycling techniques. Before reuse, PVB should be thoroughly cleaned of solid contaminants such as glass dust, fused heating wires, and other waste polymers, metals, and ceramics. This can be done by polymer dissolution and filtration. In this study, we propose the purification of PVB from contamination by dissolving the post-consumer polymeric materials into single and binary organic solvents. As part of the experimental work, measurements and optimization of the dissolution time of PVB were performed. PVB dissolves faster when a binary solvent (2-propanol + ethyl acetate) than pure 2-propanol is used. From the point of view of the practical application of PVB solutions, measurements of density and dynamic viscosity as a function of PVB concentration and temperature were performed. The PVB solutions obtained in this work can be widely used as glues for glass, ceramics, metal, impregnating, and insulating materials or as paint additives that are entirely transparent for visible light and to block UV rays.