Effect of molecular interactions on the miscibility and structure of polymer blends

Spectroscopic and Thermal Characterisation of Interpenetrating Hydrogel Networks (IHNs) Based on Polymethacrylates and Pluronics, and Their Physicochemical Stability under Aqueous Conditions

This study describes the physicochemical characterisation of interpenetrating hydrogel networks (IHNs) composed of either poly(hydroxyethylmethacrylate, p(HEMA)) or poly(methacrylic acid, p(MAA)), and Pluronic block copolymers (grades F127, P123 and L121). IHNs were prepared by mixing the acrylate monomer with Pluronic block copolymers followed by free radical polymerisation. p(HEMA)-Pluronic blends were immiscible, evident from a lack of interaction between the two components (Raman spectroscopy) and the presence of the glass transitions (differential scanning calorimetry, DSC) of the two components. Conversely, IHNs of p(MAA) and each Pluronic were miscible, displaying a single glass transition and secondary bonding between the carbonyl group of p(MAA) and the ether groups in the Pluronic block copolymers (Raman and ATR-FTIR spectroscopy). The effect of storage of the IHNs in Tris buffer on the physical state of each Pluronic and on the loss of Pluronic from the IHNs were studied using DSC and gravimetric analysis, respectively. Pluronic loss from the IHNs was dependent on the grade of Pluronic, time of immersion in Tris buffer, and the nature of the IHN (p(HEMA) or p(MAA)). At equilibrium, the loss was greater from p(HEMA) than from p(MAA) IHNs, whereas increasing ratio of poly(propylene oxide) to poly(ethylene oxide) decreased Pluronic loss. The retention of each Pluronic grade was shown to be primarily due to its micellization; however, hydrogen bonding between Pluronic and p(MAA) (but not p(HEMA)) IHNs contributed to their retention.

Design and Optimization of Molecularly Imprinted Polymer Targeting Epinephrine Molecule: A Theoretical Approach

Molecularly imprinted polymers (MIPs) are a growing highlight in polymer chemistry. They are chemically and thermally stable, may be used in a variety of environments, and fulfill a wide range of applications. Computer-aided studies of MIPs often involve the use of computational techniques to design, analyze, and optimize the production of MIPs. Limited information is available on the computational study of interactions between the epinephrine (EPI) MIP and its target molecule. A rational design for EPI-MIP preparation was performed in this study. First, density functional theory (DFT) and molecular dynamic (MD) simulation were used for the screening of functional monomers suitable for the design of MIPs of EPI in the presence of a crosslinker and a solvent environment. Among the tested functional monomers, acrylic acid (AA) was the most appropriate monomer for EPI-MIP formulation. The trends observed for five out of six DFT functionals assessed confirmed AA as the suitable monomer. The theoretical optimal molar ratio was 1:4 EPI:AA in the presence of ethylene glycol dimethacrylate (EGDMA) and acetonitrile. The effect of temperature was analyzed at this ratio of EPI:AA on mean square displacement, X-ray diffraction, density distribution, specific volume, radius of gyration, and equilibrium energies. The stability observed for all these parameters is much better, ranging from 338 to 353 K. This temperature may determine the processing and operating temperature range of EPI-MIP development using AA as a functional monomer. For cost-effectiveness and to reduce time used to prepare MIPs in the laboratory, these results could serve as a useful template for designing and developing EPI-MIPs.

Melt Processible Biodegradable Blends of Polyethylene Glycol Plasticized Cellulose Diacetate with Polylactic Acid and Polybutylene Adipate-Co-Terephthalate

Enhancing the melt processability of cellulose is key to broadening its applications. This is done via derivatization of cellulose, and subsequent plasticization and/or blending with other biopolymers, such as polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT). However, derivatization of cellulose tends to reduce its biodegradability. Moreover, traditional plasticizers are non-biodegradable. In this study, we report the influence of polyethylene glycol (PEG) plasticizer on the melt processibility and biodegradability of cellulose diacetate (CD) and its blends with PLA and PBAT. CD was first plasticized with PEG (PEG-200) at 35 wt%, and then blended with PLA and PBAT using a twin-screw extruder. Blends of the PEG plasticized CD with PLA at 40 wt% and with PBAT at 60 wt% were studied in detail. Dynamic mechanical analysis (DMA) showed that PEG reduced the glass transition of the CD from ca. 220 °C to less than 100 °C, indicating effective plasticization. Scanning electron microscopy revealed that the CD/PEG-PBAT blend had a smoother morphology implying some miscibility. The CD/PEG-PBAT blend at 60 wt% PBAT had an elongation-to-break of 734%, whereas the CD/PEG-PLA blend had a tensile strength of 20.6 MPa, comparable to that of the PEG plasticized CD. After a 108-day incubation period under simulated aerobic composting, the CD/PEG-PBAT blend at 60 wt% PBAT exhibited a biodegradation of 41%, whereas that of the CD/PEG-PLA at 40 wt% PLA was 107%. This study showed that melt processible, biodegradable CD blends can be synthesized through plasticization with PEG and blending with PBAT or PLA.

Rheo-optical Near-infrared (NIR) Analysis of Binary Amorphous Polymer Blend Consisting of Polyvinyl Chloride (PVC) and Polymethyl Methacrylate (PMMA)

A binary amorphous polymer blend consisting of polyvinyl chloride (PVC) and polymethyl methacrylate (PMMA) was studied with a rheo-optical characterization technique based on the combination of a near-infrared (NIR) spectrometer and a tensile testing machine. In rheo-optical NIR spectroscopy, tensile deformations were applied to polymers to induce the displacement of molecular chains while being probed by NIR light. The application of this technique was extended to a partially miscible amorphous polymer blend consisting of PVC and PMMA to demonstrate how it can be utilized to detect subtle but important deformation behavior. A change in the NIR spectral feature revealed that the initial deformation of the blend induces the reorientation of the PVC chains. A part of the PMMA connected to the PVC was tagged during the PVC deformation. Further deformation of the sample eventually resulted in necking propagation to the surrounding area.

Prediction of the Miscibility of PBAT/PLA Blends

Designing polymer structures and polymer blends opens opportunities to improve the performance of plastics. Blending poly(butylene adipate-co-terephthalate) (PBAT) and polylactide (PLA) is a cost-effective approach to achieve a new sustainable material with complementary properties. This study aimed to predict the theoretical miscibility of PBAT/PLA blends at the molecular level. First, the basic properties and the structure of PBAT and PLA are introduced, respectively. Second, using the group contribution methods of van Krevelen and Hoy, the Hansen and Hildebrand solubility parameters of PBAT and PLA were calculated, and the effect of the molar ratio of the monomers in PBAT on the miscibility with PLA was predicted. Third, the dependence of the molecular weight on the blend miscibility was simulated using the solubility parameters and Flory–Huggins theory. Next, the glass transition temperature of miscible PBAT/PLA blends, estimated using the Fox equation, is shown graphically. According to the prediction and simulation, the blends with a number-average molecular weight of 30 kg/mol for each component were thermodynamically miscible at 296 K and 463 K with the possibility of spinodal decomposition at 296 K and 30% volume fraction of PBAT. This study contributes to the strategic synthesis of PBAT and the development of miscible PBAT/PLA blends.

Polyethylene and Polyvinyl Chloride-Blended Polystyrene Nanofibrous Sorbents and Their Application in the Removal of Various Oil Spills

Polymers provide a wide range of properties, and these properties can be greatly enhanced and modified through polymer blending. Polymer blending combines the properties and advantages of their original polymers. This paper showcases hydrophobic polymers prepared through polymer blending; these blends are characterized and evaluated for their efficiency in the removal of crude oil spills from aqueous media. The application of these blends holds a great deal of importance in preserving the environment and the recovery of lost oil in spills. The blends are produced using polystyrene (PS) as the matrix polymer and individually blending poly(vinyl chloride) (PVC) and polyethylene (PE) with the PS consisting of proportions of 5–20 wt.% each. The blends are then electrospun into bead-free microfibers with interconnected porosities as shown by their respective scanned electron micrographs. All fibrous sorbents showed a high affinity towards the removal of crude oil, motor oil, and diesel spills. The highly viscous motor spill showed a different pattern of sorption onto fibers than that of crude oil and diesel spills. Upon comparing all the studied electrospun fibers to commercially available polypropylene fibrous sorbents, results show that the sorption efficiency of the electrospun fibers is superior. Most notably, both PS-PE5 and PS-PVC5 fibers showed to be highly more effective than commercially available polypropylene (PP) sorbents towards all types of oil spills.

Interference of Biodegradable Plastics in the Polypropylene Recycling Process

Recycling polymers is common due to the need to reduce the environmental impact of these materials. Polypropylene (PP) is one of the polymers called ‘commodities polymers’ and it is commonly used in a wide variety of short-term applications such as food packaging and agricultural products. That is why a large amount of PP residues that can be recycled are generated every year. However, the current increasing introduction of biodegradable polymers in the food packaging industry can negatively affect the properties of recycled PP if those kinds of plastics are disposed with traditional plastics. For this reason, the influence that generates small amounts of biodegradable polymers such as polylactic acid (PLA), polyhydroxybutyrate (PHB) and thermoplastic starch (TPS) in the recycled PP were analyzed in this work. Thus, recycled PP was blended with biodegradables polymers by melt extrusion followed by injection moulding process to simulate the industrial conditions. Then, the obtained materials were evaluated by studding the changes on the thermal and mechanical performance. The results revealed that the vicat softening temperature is negatively affected by the presence of biodegradable polymers in recycled PP. Meanwhile, the melt flow index was negatively affected for PLA and PHB added blends. The mechanical properties were affected when more than 5 wt.% of biodegradable polymers were present. Moreover, structural changes were detected when biodegradable polymers were added to the recycled PP by means of FTIR, because of the characteristic bands of the carbonyl group (between the band 1700–1800 cm⁻¹) appeared due to the presence of PLA, PHB or TPS. Thus, low amounts (lower than 5 wt.%) of biodegradable polymers can be introduced in the recycled PP process without affecting the overall performance of the final material intended for several applications, such as food packaging, agricultural films for farming and crop protection.

Influence of acrylonitrile butadiene rubber on recyclability of blends prepared from poly(vinyl chloride) and poly(methyl methacrylate)

The current investigation deals with the recycling possibilities of poly(vinyl chloride) and poly(methyl methacrylate) in the presence of acrylonitrile butadiene rubber. Recycled blends of poly(vinyl chloride)/poly(methyl methacrylate) are successfully formed from the plastic constituents, those are recovered from waste computer products. However, lower impact performance of the blend and lower stability of the poly(vinyl chloride) phase in the recycled blend restricts its further usage in industrial purposes. Therefore, effective utilisation acrylonitrile butadiene rubber in a recycled blend was considered for improving mechanical and thermal performance. Incorporation of acrylonitrile butadiene rubber resulted in the improvement in impact performance as well as elongation-at-break of the recycled blend. The optimum impact performance was found in the blend with 9 wt% acrylonitrile butadiene rubber, which shows 363% of enhancement as compared with its parent blend. Moreover, incorporated acrylonitrile butadiene rubber also stabilises the poly(vinyl chloride) phase present in the recycled blend, similarly Fourier transform infrared spectroscopy studies indicate the interactions of various functionalities present in the recycled blend and acrylonitrile butadiene rubber. In addition to this, thermogravimetric analysis indicates the improvement in the thermal stability of the recycled blend after the addition of acrylonitrile butadiene rubber into it. The existence of partial miscibility in the recycled blend was identified using differential scanning calorimetry and scanning electron microscopy.

Transparent Blend of Poly(Methylmethacrylate)/Cellulose Acetate Butyrate for the Protection from Ultraviolet

The use of transparent polymers as an alternative to glass has become widespread. However, the direct exposure of these materials to climatic conditions of sunlight and heat decrease the lifetime cost of these products. The aim of this study was to minimize the harm caused by ultraviolet (UV) radiation exposure to transparent poly(methylmethacrylate) (PMMA), which usually leads to changes in the physical and chemical properties of these materials and reduced performance. This was achieved using environmentally friendly cellulose acetate butyrate (CAB). The optical, morphological, and thermal properties of CAB blended with transparent PMMA was studied using UV-VIS spectrophotometry, scanning electron microscopy, X-ray diffraction, dynamic mechanical analysis, and thermal gravimetric analysis. The results show that CAB was able to reduce the effects of UV radiation by making PMMA more transparent to UV light, thereby preventing the negative effects of trapped radiation within the compositional structure, while maintaining the amorphous structure of the blend. The results also show that CAB blended with PMMA led to some properties commensurate with the requirements of research in terms of a slight increase in the value of the modulus and the glass transition temperature for the PMMA/CAB blend.

Molecular interaction studies of amorphous solid dispersions of the antimelanoma agent betulinic acid

Betulinic acid (BA), a novel natural product with antimelanoma activity, has poor aqueous solubility (<0.1 μg/mL) and therefore exhibits poor bioavailability. The purpose of this study was to explore the feasibility of preparing BA solid dispersions (BA-SDs) with hydrophilic polymers to enhance the aqueous solubility of BA. Melt-quenched solid dispersions (MQ-SDs) of BA were prepared at various ratios with the hydrophilic polymers including Soluplus, HPMCAS-HF, Kollidon VA64, Kollidon K90, and Eudragit RLPO. BA was found to be miscible in all polymers at a 1:4 (w/w) ratio by modulated differential scanning calorimetry (MDSC). BA/Soluplus MQ-SD exhibited the highest solubility in simulated body fluids followed by BA/Kollidon VA64 MQ-SD. The MQ-SDs of BA/Soluplus, BA/HPMCAS-HF, and BA/Kollidon VA64 were found to be amorphous as indicated by X-ray powder diffraction (XRPD) studies. Fourier transform infra-red (FT-IR) studies indicated molecular interactions between BA and Soluplus. Our preliminary screening of polymers indicates that Soluplus and Kollidon VA64 exhibit the greatest potential to form BA-SDs.

Monte Carlo simulations of the phase separation of a copolymer blend in a thin film

Monte Carlo simulations were carried out to study the phase separation of a copolymer blend comprising an alternating copolymer and/or block copolymer in a thin film, and a phase diagram was constructed with a series of composed recipes. The effects of composition and segregation strength on phase separation were discussed in detail. The chain conformation of the block copolymer and alternating copolymer were investigated with changes of the segregation strength. Our simulations revealed that the segment distribution along the copolymer chain and the segregation strength between coarse-grained beads are two important parameters controlling phase separation and chain conformation in thin films of a copolymer blend. A well-controlled phase separation in the copolymer blend can be used to fabricate novel nanostructures.

Simultaneous enhancement in mechanical strength, electrical conductivity, and electromagnetic shielding properties in PVDF–ABS blends containing PMMA wrapped multiwall carbon nanotubes

A unique approach was adopted to drive the multiwall carbon nanotubes (MWNTs) to the interface of immiscible PVDF–ABS blends by wrapping the nanotubes with a mutually miscible homopolymer (PMMA).

Cellulose acetate butyrate/poly(caprolactonetriol) blends: Miscibility, mechanical properties, and in vivo inflammatory response

This study reports the results of the characterization of cellulose acetate butyrate and polycaprolactone-triol blends in terms of miscibility, swelling capacity, mechanical properties, and inflammatory response in vivo. The cellulose acetate butyrate film was opaque and rigid, with glass transition (T g ) at 134℃ and melting temperature of 156℃. The cellulose acetate butyrate/polycaprolactone-triol films were transparent up to a polycaprolactone-triol content of 60%. T g of the cellulose acetate butyrate films decreased monotonically as polycaprolactone-triol was added to the blend, thus indicating miscibility. FTIR spectroscopy revealed a decrease in intramolecular hydrogen bonding in polycaprolactone-triol, whereas no hydrogen bonding was observed between cellulose acetate butyrate and -OH from polycaprolactone-triol. The increase in polycaprolactone-triol content in the blend decreased the water uptake. An increase in polycaprolactone-triol content decreased the modulus of elasticity and increased the elongation at break. A cellulose acetate butyrate/polycaprolactone-triol 70/30 blend implanted in rats showed only an acute inflammatory response 7 days after surgery. No change in inflammation mediators was observed.

Characterization and recovery of polymers from mobile phone scrap

Electronic scrap is part of a universally wide range of obsolete, defective, or used materials that need to be disposed of or recycled in an ecologically friendly manner. The present study focused on the polymers present in mobile phone scrap. In mobile phones, polymers are found in frames and in printed circuit boards (PCBs). The frames are mainly made of polymers whereas PCBs use a variety of material (polymers, ceramics, and metals) which makes recycling more difficult. As a first step, mobile phones were collected, separated by manufacturer/model, and weighed, and the principal polymer types identified. The frames and PCBs were processed separately. The metals in PCBs were separated out by an electrostatic separation process. The resulting polymeric material was identified and mixed with the polymers of frames to fabricate the samples. Two types of samples were made: one with polymeric frames, and the other with a mixture of frames and polymeric fraction from the PCBs. Both kinds of sample were fabricated by injection moulding. The samples were evaluated by mechanical tests (tensile, impact, and hardness) to verify the feasibility of recycling the polymers present in mobile phone scrap. The results demonstrated the technical viability of recovering polymers using mechanical processing followed by an injection process.