Valorization of residual lignin from corncob residues into thermosensitive lignin-based "molecular glues" for recycling cellulase

The cost of enzymolysis is a major bottleneck for the industrialisation of lignocellulosic enzymatic hydrolysis technology, and recycling cellulase can reduce this cost. Herein, a sulfobetaine prepolymer (CPS) with terminal chlorine was grafted onto enzymatic hydrolysis residual lignin (EHL) from corncob to construct thermosensitive lignin-based "molecular glues" (lignin-based sulfobetaine polymers, L-CPS) that were used to recover and recycle cellulase. L-CPS2 (1.0 g/L) was added to the corncob residue (CCR) enzymolysis system (50 °C, pH 4.5). After hydrolysis, L-CPS2 co-precipitated with cellulase through hydrophobic binding when cooling to 25 °C. This co-precipitation decreased the amount of cellulase by 40 %. In summary, a thermally responsive lignin-based molecular glue was constructed for green recycling of cellulase, providing a new approach to decreasing the cost of lignocellulosic enzymolysis and high value utilisation of industrial lignin.

A preliminary study of the temperature-responsive selective extraction performance of hydrogel derived from sulfobetaine methacrylate

BACKGROUND

The limited extraction selectivity caused by the single extraction selection mechanism of solid phase extraction (SPE) technology is one of the bottlenecks restricting its development. The development of environmentally sensitive materials provides a new opportunity to solve this problem. Based on this, we developed the sulfobetaine methacrylate hydrogel with abundant pore structure, a large number of adsorption sites and especially temperature responsiveness, and used as adsorbent for the extraction of pesticide residues in lychees.

RESULTS

The new hydrogel adsorbent was prepared by free radical copolymerization with sulfobetaine methacrylate as monomer, and used for the extraction of benzoylurea insecticides from lychees. Interestingly, the hydrogel showed an almost opposite temperature-selective extraction trend for different benzoylurea insecticides with similar structure and polarity, and opposite hydrophilicity, which may be caused by the temperature-sensitive and the special action site of the hydrogel, and the change of the diffusion of aqueous solution. In addition, the analysis method of three hydrophilic benzoylurea insecticides by sulfobetaine methacrylate hydrogel-SPE-HPLC was established. Under optimal conditions, the low limits of detection (0.030 μg L-1) and quantification (0.10 μg L-1), and the wide linear ranges (0.10-50.0 μg L-1) were achieved. Its application in lychee samples were also tested, and the satisfactory results were obtained, with the spiked recoveries from 80.79 % to 108.31 %.

SIGNIFICANCE

This was a great breakthrough in the selective extraction of similar targets. These properties, combined with low-cost, biodegradable raw materials and convenient, green synthesis method make the sulfobetaine methacrylate hydrogel a very promising solid phase adsorbent. Temperature-responsive selective mode can greatly enrich the selective extraction mechanism and promote its development and application in complex actual samples.

A Comprehensive Review of Stimuli-Responsive Smart Polymer Materials-Recent Advances and Future Perspectives

Today, smart materials are commonly used in various fields of science and technology, such as medicine, electronics, soft robotics, the chemical industry, the automotive field, and many others. Smart polymeric materials hold good promise for the future due to their endless possibilities. This group of advanced materials can be sensitive to changes or the presence of various chemical, physical, and biological stimuli, e.g., light, temperature, pH, magnetic/electric field, pressure, microorganisms, bacteria, viruses, toxic substances, and many others. This review concerns the newest achievements in the area of smart polymeric materials. The recent advances in the designing of stimuli-responsive polymers are described in this paper.

Strong and Thermo-Switchable Gel Adhesion Based on UCST-Type Phase Transition in Deep Eutectic Solvent

It remains a great challenge to achieve strong and reversible hydrogel adhesion. Hydrogel adhesives also suffer from poor environmental stability due to dehydration. To overcome these problems, here reversible adhesive gels are designed using a new switching mechanism and new solvent. For the first time, the study observes UCST (upper critical solution temperature)-type thermosensitive behaviors of poly(benzyl acrylate) (PBnA) polymer and gel in menthol:thymol deep eutectic solvents (DESs). The temperature-induced phase transition allows adjusting cohesive force, and hence adhesion strength of PBnA gels by temperature. To further improve the mechanical and adhesion properties, a peptide crosslinker is used to allow energy dissipation when deforming. The resulting eutectogel exhibits thermal reversible adhesion with a high switching ratio of 14.0. The adhesion strength at attachment state reaches 0.627 MPa, which is much higher than most reversible adhesive hydrogels reported before. The low vapor pressure of DES endows the gel excellent environmental stability. More importantly, the gel can be repeatedly switched between attachment and detachment states. The strong and reversible gel adhesive is successfully used to design soft gripper for the transport of heavy cargos and climbing robot capable of moving on vertical and inverted surface in a manner similar to gecko.

Unravelling the interactions between small molecules and liposomal bilayers via molecular dynamics and thermodynamic modelling

Lipid-based drug delivery systems hold immense promise in addressing critical medical needs, from cancer and neurodegenerative diseases to infectious diseases. By encapsulating active pharmaceutical ingredients - ranging from small molecule drugs to proteins and nucleic acids - these nanocarriers enhance treatment efficacy and safety. However, their commercial success faces hurdles, such as the lack of a systematic design approach and the issues related to scalability and reproducibility. This work aims to provide insights into the drug-phospholipid interaction by combining molecular dynamic simulations and thermodynamic modelling techniques. In particular, we have made a connection between the structural properties of the drug-phospholipid system and the physicochemical performance of the drug-loaded liposomal nanoformulations. We have considered two prototypical drugs, felodipine (FEL) and naproxen (NPX), and one model hydrogenated soy phosphatidylcholine (HSPC) bilayer membrane. Molecular dynamic simulations revealed which regions within the phospholipid bilayers are most and least favoured by the drug molecules. NPX tends to reside at the water-phospholipid interface and is characterized by a lower free energy barrier for bilayer membrane permeation. Meanwhile, FEL prefers to sit within the hydrophobic tails of the phospholipids and is characterized by a higher free energy barrier for membrane permeation. Flory-Huggins thermodynamic modelling, small angle X-ray scattering, dynamic light scattering, TEM, and drug release studies of these liposomal nanoformulations confirmed this drug-phospholipid structural difference. The naproxen-phospholipid system has a lower free energy barrier for permeation, higher drug miscibility with the bilayer, larger liposomal nanoparticle size, and faster drug release in the aqueous medium than felodipine. We suggest that this combination of molecular dynamics and thermodynamics approach may offer a new tool for designing and developing lipid-based nanocarriers for unmet medical applications.

Dipole Theory of Polyzwitterion Microgels and Gels

The behavior of polyzwitterions, constituted by dipole-like zwitterionic monomers, is significantly different from that of uniformly charged polyelectrolytes. The origin of this difference lies in the intrinsic capacity of polyzwitterions to self-associate intramolecularly and associate with interpenetrating chains driven by dominant dipolar interactions. Earlier attempts to treat polyzwitterions implicitly assume that the dipoles of zwitterion monomers are randomly oriented. At ambient temperatures, the dipolar zwitterion monomers can readily align with each other generating quadrupoles and other multipoles and thus generating heterogeneous structures even in homogeneous solutions. Towards an attempt to understand the role of such dipolar associations, we present a mean field theory of solutions of polyzwitterions. Generally, we delineate a high-temperature regime where the zwitterion dipoles are randomly oriented from a low-temperature regime where quadrupole formation is significantly prevalent. We present closed-form formulas for: (1) Coil-globule transition in the low-temperature regime, the anti-polyelectrolyte effect of chain expansion upon addition of low molar mass salt, and chain relaxation times in dilute solutions. (2) Spontaneous formation of a mesomorphic state at the borderline between the high-temperature and low-temperature regimes and its characteristics. A universal law is presented for the radius of gyration of the microgel, as a proportionality to one-sixth power of the polymer concentration. (3) Swelling equilibrium of chemically cross-linked polyzwitterion gels in both the high temperature and low-temperature regimes. Addressing the hierarchical internal dynamics of polyzwitterion gels, we present a general stretched exponential law for the time-correlation function of gel displacement vector, that can be measured in dynamic light scattering experiments. The present theory is of direct experimental relevance and additional theoretical developments to all polyzwitterion systems, and generally to biological macromolecular systems such as intrinsically disordered proteins.

Modern Trends in Polymerization-Induced Self-Assembly

Polymerization-induced self-assembly (PISA) is a powerful and versatile technique for producing colloidal dispersions of block copolymer particles with desired morphologies. Currently, PISA can be carried out in various media, over a wide range of temperatures, and using different mechanisms. This method enables the production of biodegradable objects and particles with various functionalities and stimuli sensitivity. Consequently, PISA offers a broad spectrum of potential commercial applications. The aim of this review is to provide an overview of the current state of rational synthesis of block copolymer particles with diverse morphologies using various PISA techniques and mechanisms. The discussion begins with an examination of the main thermodynamic, kinetic, and structural aspects of block copolymer micellization, followed by an exploration of the key principles of PISA in the formation of gradient and block copolymers. The review also delves into the main mechanisms of PISA implementation and the principles governing particle morphology. Finally, the potential future developments in PISA are considered.

UCST-Type Thermoresponsive Sol-Gel Transition Triblock Copolymer Containing Zwitterionic Polymer Blocks

Thermoresponsive sol-gel transition polymers are of significant interest because of their fascinating biomedical applications, including as drug reservoirs for drug delivery systems and scaffolds for tissue engineering. Although extensive research has been conducted on lower critical solution temperature (LCST)-type sol-gel transition polymers, there have been few reports on upper critical solution temperature (UCST)-type sol-gel transition polymers. In this study, we designed an ABA-type triblock copolymer composed of a poly(ethylene glycol) (PEG) block and zwitterionic polymer blocks that exhibit UCST-type thermoresponsive phase transitions. A sulfobetaine (SB) monomer with both ammonium and sulfonate (-SO3) groups in its side chain or a sulfabetaine (SaB) monomer with both ammonium and sulfate (-OSO3) groups in its side chain was polymerized from both ends of the PEG block via reversible addition-fragmentation chain-transfer (RAFT) polymerization to obtain PSB-PEG-PSB and PSaB-PEG-PSaB triblock copolymers, respectively. Although an aqueous solution containing the PSB-PEG-PSB triblock copolymer showed an increase in viscosity upon cooling, it did not undergo a sol-to-gel transition. In contrast, a sol-to-gel transition was observed when a phosphate-buffered saline containing PSaB-PEG-PSaB was cooled from 80 °C to 25 °C. The PSaB blocks with -OSO3 groups exhibited a stronger dipole-dipole interaction than conventional SB with -SO3 groups, leading to intermolecular association and the formation of a gel network composed of PSaB assemblies bridged with PEG. The fascinating UCST-type thermoresponsive sol-gel transition properties of the PSaB-PEG-PSaB triblock copolymer suggest that it can provide a useful platform for designing smart biomaterials, such as drug delivery reservoirs and cell culture scaffolds.

One Stone Several Birds: Self-Localizing Submicrocages With Dual Loading Points for Multifunctional Drug Delivery

As the core index, how to improve bioavailability of loaded cargoes is a hot topic of drug carriers. In this study, aminated β-cyclodextrin (β-CD) as a cross-linking points is first integrated into 3D poly(acrylamide-co-acrylonitrile) (P(AAm-co-AN)) network to build up a unique submicrocage (466.2 ± 47.6 nm), featuring upper critical solution temperature (UCST; ≈40 °C), high volume expansion coefficient, and excellent biocompatibility. Hereinto, hydrophobic β-elemene (ELE) is locally loaded in β-CD with high loading efficiency (8.72%) and encapsulation efficiency (78.60%) through hydrophobic desolvation and host-guest interaction. Above UCST, the release of the loaded ELE is accelerated to 72.87% in 24 h, together with the enhanced sensitization effect of synergized radiotherapy. Given spontaneous long-lasting delivery, targeted embolization, and post-treatment removal of such UCST-type submicrocage, it is anticipated to provide a novel, facile, efficient, and versatile strategy of comprehensive anticancer treatments for high drug bioavailability.

Genetically Fused Resilin-like Polypeptide-Coiled Coil Bundlemer Conjugates Exhibit Tunable Multistimuli-Responsiveness and Undergo Nanofibrillar Assembly

Peptide-based materials are diverse candidates for self-assembly into modularly designed and stimuli-responsive nanostructures with precisely tunable compositions. Here, we genetically fused computationally designed coiled coil-forming peptides to the N- and C-termini of compositionally distinct multistimuli-responsive resilin-like polypeptides (RLPs) of various lengths. The successful expression of these hybrid polypeptides in bacterial hosts was confirmed through techniques such as gel electrophoresis, mass spectrometry, and amino acid analysis. Circular dichroism spectroscopy and ultraviolet-visible turbidimetry demonstrated that despite the fusion of disparate structural and responsive units, the coiled coils remained stable in the hybrid polypeptides, and the sequence-encoded differences in thermoresponsive phase separation of the RLPs were preserved. Cryogenic transmission electron microscopy and coarse-grained modeling showed that after thermal annealing in solution, the hybrid polypeptides adopted a closed loop conformation and assembled into nanofibrils capable of further hierarchically organizing into cluster structures and ribbon-like structures mediated by the self-association tendency of the RLPs.

Biomedical applications of stimuli-responsive "smart" interpenetrating polymer network hydrogels

In recent years, owing to the ongoing advancements in polymer materials, hydrogels have found increasing applications in the biomedical domain, notably in the realm of stimuli-responsive "smart" hydrogels. Nonetheless, conventional single-network stimuli-responsive "smart" hydrogels frequently exhibit deficiencies, including low mechanical strength, limited biocompatibility, and extended response times. In response, researchers have addressed these challenges by introducing a second network to create stimuli-responsive "smart" Interpenetrating Polymer Network (IPN) hydrogels. The mechanical strength of the material can be significantly improved due to the topological entanglement and physical interactions within the interpenetrating structure. Simultaneously, combining different network structures enhances the biocompatibility and stimulus responsiveness of the gel, endowing it with unique properties such as cell adhesion, conductivity, hemostasis/antioxidation, and color-changing capabilities. This article primarily aims to elucidate the stimulus-inducing factors in stimuli-responsive "smart" IPN hydrogels, the impact of the gels on cell behaviors and their biomedical application range. Additionally, we also offer an in-depth exposition of their categorization, mechanisms, performance characteristics, and related aspects. This review furnishes a comprehensive assessment and outlook for the advancement of stimuli-responsive "smart" IPN hydrogels within the biomedical arena. We believe that, as the biomedical field increasingly demands novel materials featuring improved mechanical properties, robust biocompatibility, and heightened stimulus responsiveness, stimuli-responsive "smart" IPN hydrogels will hold substantial promise for wide-ranging applications in this domain.

Introducing UCST onto Chitosan for a Simple and Effective Single-Phase Extraction

Upper critical solution temperature (UCST) polymers undergo their own collapsed structures to show thermoresponsive functions favoring controlled release systems, cell adhesion, including separation process, etc. Although the copolymerization of UCST monomers with other vinyl monomers containing a pendant group is a good way to introduce additional functions, uncertain UCST performance as well as extensive bio-related properties are always the points to be considered. To accomplish this, the present work proposes the application of polysaccharides, i.e., chitosan (CS), as the biopolymer backbone to conjugate with functional molecules and UCST polymers. The use of chain transfer agents, e.g., mercaptoacetic acid, in radical polymerization with UCST poly(methacrylamide) (PMAAm) via the CS/NHS (N-hydroxysuccinimide) complex allows the simple water-based modification. The further conjugation of mouse anti-LipL32 IgG monoclonal antibody (anti-LipL32 mAb) onto CS-PMAAm (CS-PMAAm-Ab) enables a selective binding of recombinant LipL32 (rLipL32) antigen (Ag) in the solution. The CS-PMAAm obtained not only shows the cloud point in the range of 10-30 °C but also the extraction of rLipL32 because of CS-PMAAm-Ab-Ag aggregation. The present work demonstrates how CS expresses UCST with additional antibody conjugated is feasible for a simple and effective Ag single-phase extraction.

Regulating Electrostatic Interactions toward Thermoresponsive Hydrogels with Low Critical Solution Temperature

Low critical solution temperature (LCST) of commonly used thermoresponsive polymers in water is basically dominated by hydrophobic interactions. Herein, a novel thermoresponsive system based on electrostatic interactions is reported. By simply loading aluminum chloride (AlCl3 ) into non-responsive poly(2-hydroxyethyl acrylate) (PHEA) hydrogels, PHEA-Al gels turn to have reversible thermoresponsive behavior between transparent and opaque without any volume change. Further investigations by changing metal ion-polymer compositions unravel the necessity of specific electrostatic interactions, namely, cation-dipole bonding interactions between hydroxy groups and trivalent metal ions. The thermoresponsive hydrogel demonstrates high transparency (≈95%), excellent luminous modulation capability (>98%), and cyclic reliability, suggesting great potential as an energy-saving material. Although LCST control by salt addition is widely known, salt-induced expression of thermoresponsiveness has barely been discussed before. This design provides a new approach of easy fabrication, low cost, and scalability to develop stimuli-responsive materials.

Structural Determinants of Stimuli-Responsiveness in Amphiphilic Macromolecular Nano-assemblies

Stimuli-responsive nano-assemblies from amphiphilic macromolecules could undergo controlled structural transformations and generate diverse macroscopic phenomenon under stimuli. Due to the controllable responsiveness, they have been applied for broad material and biomedical applications, such as biologics delivery, sensing, imaging, and catalysis. Understanding the mechanisms of the assembly-disassembly processes and structural determinants behind the responsive properties is fundamentally important for designing the next generation of nano-assemblies with programmable responsiveness. In this review, we focus on structural determinants of assemblies from amphiphilic macromolecules and their macromolecular level alterations under stimuli, such as the disruption of hydrophilic-lipophilic balance (HLB), depolymerization, decrosslinking, and changes of molecular packing in assemblies, which eventually lead to a series of macroscopic phenomenon for practical purposes. Applications of stimuli-responsive nano-assemblies in delivery, sensing and imaging were also summarized based on their structural features. We expect this review could provide readers an overview of the structural considerations in the design and applications of nanoassemblies and incentivize more explorations in stimuli-responsive soft matters.

Review of the Perspectives and Study of Thermo-Responsive Polymer Gels and Applications in Oil-Based Drilling Fluids

Thermoresponsive polymer gels are a type of intelligent material that can react to changes in temperature. These materials possess excellent innovative properties and find use in various fields. This paper systematically analyzes the methods for testing and regulating phase transition temperatures of thermo-responsive polymer gels based on their response mechanism. The report thoroughly introduces the latest research on thermo-responsive polymer gels in oil and gas extraction, discussing their advantages and challenges across various environments. Additionally, it elucidates how the application limitations of high-temperature and high-salt conditions can be resolved through process optimization and material innovation, ultimately broadening the scope of application of thermo-responsive polymer gels in oil and gas extraction. The article discusses the technological development and potential applications of thermo-responsive polymer gels in oil-based drilling fluids. This analysis aims to offer researchers in the oil and gas industry detailed insights into future possibilities for thermo-responsive polymer gels and to provide helpful guidance for their practical use in oil-based drilling fluids.

Smart and programmed thermo-wetting yarns for scalable and customizable moisture/heat conditioning textiles

Programmable smart textiles with adaptive moisture/heat conditioning (MHC) capabilities are globally being sought to meet the requirements of comfort, energy efficiency, and health protection. However, a universal strategy for fabricating truly scalable and customizable MHC textiles is lacking. In this study, we introduce a scalable in situ grafting approach for the continuous fabrication of two series of smart textile yarns with opposite thermoresponsive wetting behaviors. In particular, the wetting transition temperature can be precisely programmed by adjusting the grafting formula, making the yarns highly customizable. The smart yarns demonstrated excellent mechanical strength, whiteness, weavability, biocompatibility, and washability (with more than 60 home washes), comparable to those of regular textile yarns. They can serve as building blocks independently or in combination to create smart textiles with adaptive sweat wicking and intelligent moisture/heat regulation capabilities. A proposed hybrid textile integrating both the two series of smart yarns can offer dry-contact and cooling/keep-warming effects of approximately 1.6/2.8 °C, respectively, in response to changes in ambient temperature. Our method provides a rich array of design options for nonpowered MHC textiles while maintaining a balance between traditional wearing conventions and large-scale production.

Thermo-Responsive Hydrogels Coupled with Photothermal Agents for Biomedical Applications

Intelligent hydrogels are materials with abilities to change their chemical nature or physical structure in response to external stimuli showing promising potential in multitudinous applications. Especially, photo-thermo coupled responsive hydrogels that are prepared by encapsulating photothermal agents into thermo-responsive hydrogel matrix exhibit more attractive advantages in biomedical applications owing to their spatiotemporal control and precise therapy. This work summarizes the latest progress of the photo-thermo coupled responsive hydrogel in biomedical applications. Three major elements of the photo-thermo coupled responsive hydrogel, i.e., thermo-responsive hydrogel matrix, photothermal agents, and construction methods are introduced. Furthermore, the recent developments of these hydrogels for biomedical applications are described with some selected examples. Finally, the challenges and future perspectives for photo-thermo coupled responsive hydrogels are outlined.

Synergistic Approaches in the Design and Applications of UCST Polymers

This review summarizes recent progress in the synergistic design strategy for thermoresponsive polymers possessing an upper critical solution temperature (UCST) in aqueous systems. To achieve precise control of the responsive behavior of the UCST polymers, their molecular design can benefit from a synergistic effect of hydrogen bonding with other interactions or modification of the chemical structures. The combination of UCST behavior with other stimuli-responsive properties of the polymers may yield new functional materials with potential applications such as sensors, actuators, and controlled release devices. The advances in this area provide insight or inspiration into the understanding and design of functional UCST polymers for a wide range of applications.

Stimuli-Responsive and Multifunctional Nanogels in Drug Delivery

Nanogels represent promising drug delivery systems in the biomedical field, designed to overcome challenges associated with standard treatment approaches. Stimuli-responsive nanogels, often referred to as intelligent materials, have garnered significant attention for their potential to enhance control over properties such as drug release and targeting. Furthermore, researchers have recently explored the application of nanogels in diverse sectors beyond biomedicine including sensing materials, catalysts, or adsorbents for environmental applications. However, to fully harness their potential as practical delivery systems, further research is required to better understand their pharmacokinetic behaviour, interactions between nanogels and bio distributions, as well as toxicities. One promising future application of stimuli-responsive multifunctional nanogels is their use as delivery agents in cancer treatment, offering an alternative to overcome the challenges with conventional approaches. This review discusses various synthetic methods employed in developing nanogels as efficient carriers for drug delivery in cancer treatment. The investigations explore, the key aspects of nanogels, including their multifunctionality and stimuli-responsive properties, as well as associated toxicity concerns. The discussions presented herein aim to provide the readers a comprehensive understanding of the potential of nanogels as smart drug delivery systems in the context of cancer therapy.

Polyzwitterion fast and slow mode behavior are coupled to phase separation as observed by dynamic laser light scattering

A model zwitterionic polysulfobetaine, poly(3-(acrylamidopropyl-dimethyl-ammonium) propyl-1-sulfonate) (pAPAPS), phase separates upon cooling and exhibits an upper critical solution temperature (UCST) behavior with no added salt in deuterium oxide solutions. Dynamic light scattering measurements indicate the presence of distinct fast and slow diffusive modes, where the fast mode is interpreted as a collective diffusion coefficient and the slow mode is attributed to the diffusion of multi-chain dynamic clusters. The relative population of fast and slow modes varies systematically with temperature and concentration. A clustering temperature (T*) was assigned when the slow mode first appeared upon cooling. The slow mode then increases in relative scattering amplitude as the phase boundary is approached. The fast mode exhibits a concentration dependence above T* consistent with the virial expansion in the collective diffusion. The sign of the virial coefficient (kd) is negative, even in the good solvent region above the expected Flory temperature (Θ ≈ 39 °C), a behavior distinct from synthetic neutral polymers in organic solvents. The onset of multi-chain clustering at T < T* coincides with the poor solvent regime (T < Θ). Attractive dipolar interactions due to the zwitterionic sulfobetaine groups in pAPAPS are suggested as the origin of the multi-chain clusters with no salt. Upon the addition of 100 mM NaCl, the slow mode is suppressed, and the hydrodynamic radius is consistent with polyzwitterion chain dimensions in a dilute solution. We find that concentration dependent diffusion is highly linked to the theta temperature and the emergence of dynamic clusters as the polymer goes from good to poor solvent on approach to the UCST. The slow mode in the semidilute regime is reported along with preliminary small-angle neutron scattering data that show salt reduces clustering and leads to predominantly chain scattering.

Lignin-grafted quaternary ammonium phosphate with temperature and pH responsive behavior for improved enzymatic hydrolysis and cellulase recovery

The cost of lignocellulosic enzymatic hydrolysis was reduced by enhancing enzymatic hydrolysis and recycling cellulase. Lignin-grafted quaternary ammonium phosphate (LQAP) with sensitive temperature and pH response, was obtained by grafting quaternary ammonium phosphate (QAP) onto enzymatic hydrolysis lignin (EHL). LQAP dissolved under the hydrolysis condition (pH 5.0, 50 °C) and enhanced the hydrolysis. After hydrolysis, LQAP and cellulase co-precipitated by the hydrophobic binding and electrostatic attraction, when lowering pH to 3.2, and cooling to 25 °C. LQAP had significant performances of pH-UCST response, enzymatic hydrolysis enhancement and cellulase recovery at the same time. When 3.0 g/L LQAP-100 was added to the system of corncob residue, SED@48 h increased from 62.6 % to 84.4 %, and 50 % of amount of cellulase was saved. Precipitation of LQAP at low temperature was mainly attributed to the salt formation of positive and negative ions in QAP; LQAP enhanced the hydrolysis for its ability to decrease the ineffective adsorption of cellulase by forming a hydration film on lignin and through the electrostatic repulsion. In this work, a lignin amphoteric surfactant with temperature response, was used to enhance hydrolysis and recover cellulase. This work will provide a new idea for reducing the cost of lignocellulose-based sugar platform technology, and high-value utilization of industrial lignin.

The conformational phase diagram of neutral polymers in the presence of attractive crowders

Extensive coarse-grained molecular dynamics simulations are performed to investigate the conformational phase diagram of a neutral polymer in the presence of attractive crowders. We show that, for low crowder densities, the polymer predominantly shows three phases as a function of both intra-polymer and polymer-crowder interactions: (1) weak intra-polymer and weak polymer-crowder attractive interactions induce extended or coil polymer conformations (phase E), (2) strong intra-polymer and relatively weak polymer-crowder attractive interactions induce collapsed or globular conformations (phase CI), and (3) strong polymer-crowder attractive interactions, regardless of intra-polymer interactions, induce a second collapsed or globular conformation that encloses bridging crowders (phase CB). The detailed phase diagram is obtained by determining the phase boundaries delineating the different phases based on an analysis of the radius of gyration as well as bridging crowders. The dependence of the phase diagram on strength of crowder-crowder attractive interactions and crowder density is clarified. We also show that when the crowder density is increased, a third collapsed phase of the polymer emerges for weak intra-polymer attractive interactions. This crowder density-induced compaction is shown to be enhanced by stronger crowder-crowder attraction and is different from the depletion-induced collapse mechanism, which is primarily driven by repulsive interactions. We also provide a unified explanation of the observed re-entrant swollen/extended conformations of the earlier simulations of weak and strongly self-interacting polymers in terms of crowder-crowder attractive interactions.

Synthesis of NVCL-NIPAM Hydrogels Using PEGDMA as a Chemical Crosslinker for Controlled Swelling Behaviours in Potential Shapeshifting Applications

Stimuli-responsive hydrogels have recently gained interest within shapeshifting applications due to their capabilities to expand in water and their altering swelling properties when triggered by stimuli, such as pH and heat. While conventional hydrogels lose their mechanical strength during swelling, most shapeshifting applications require materials to have mechanical strength within a satisfactory range to perform specified tasks. Thus, stronger hydrogels are needed for shapeshifting applications. Poly (N-isopropylacrylamide) (PNIPAm) and poly (N-vinyl caprolactam) (PNVCL) are the most popular thermosensitive hydrogels studied. Their close-to-physiological lower critical solution temperature (LCST) makes them superior candidates in biomedicine. In this study, copolymers made of NVCL and NIPAm and chemically crosslinked using poly (ethylene glycol) dimethacrylate (PEGDMA) were fabricated. Successful polymerisation was proven via Fourier transform infrared spectroscopy (FTIR). The effects of incorporating comonomer and crosslinker on the LCST were found minimal using cloud-point measurements, ultraviolet (UV) spectroscopy, and differential scanning calorimetry (DSC). Formulations that completed three cycles of thermo-reversing pulsatile swelling are demonstrated. Lastly, rheological analysis validated the mechanical strength of PNVCL, which was improved due to the incorporation of NIPAm and PEGDMA. This study showcases potential smart thermosensitive NVCL-based copolymers that can be applied in the biomedical shapeshifting area.

Zwitterionic Biomaterials

The term "zwitterionic polymers" refers to polymers that bear a pair of oppositely charged groups in their repeating units. When these oppositely charged groups are equally distributed at the molecular level, the molecules exhibit an overall neutral charge with a strong hydration effect via ionic solvation. The strong hydration effect constitutes the foundation of a series of exceptional properties of zwitterionic materials, including resistance to protein adsorption, lubrication at interfaces, promotion of protein stabilities, antifreezing in solutions, etc. As a result, zwitterionic materials have drawn great attention in biomedical and engineering applications in recent years. In this review, we give a comprehensive and panoramic overview of zwitterionic materials, covering the fundamentals of hydration and nonfouling behaviors, different types of zwitterionic surfaces and polymers, and their biomedical applications.

Thermoresponsive Block Copolymer Core-Shell Nanoparticles with Tunable Flow Behavior in Porous Media

With the purpose of investigating new polymeric materials as potential flow modifiers for their future application in enhanced oil recovery (EOR), a series of amphiphilic poly(di(ethylene glycol) methyl ether methacrylate-co-oligo(ethylene glycol) methyl ether methacrylate) [P(DEGMA-co-OEGMA)]-based core-shell nanoparticles were prepared by aqueous reversible addition-fragmentation chain transfer-mediated polymerization-induced self-assembly. The developed nano-objects were shown to be thermoresponsive, demonstrating a reversible lower-critical solution temperature (LCST)-type phase transition with increasing solution temperature. Characterization of their thermoresponsive nature by variable-temperature UV-vis and dynamic light scattering analyses revealed that these particles reversibly aggregate when heated above their LCST and that the critical transition temperature could be accurately tuned by simply altering the molar ratio of core-forming monomers. Sandpack experiments were conducted to evaluate their pore-blocking performance at low flow rates in a porous medium heated at temperatures above their LCST. This analysis revealed that particles aggregated in the sandpack column and caused pore blockage with a significant reduction in the porous medium permeability. The developed aggregates and the increased pressure generated by the blockage were found to remain stable under the injection of brine and were observed to rapidly dissipate upon reducing the temperature below the LCST of each formulation. Further investigation by double-column sandpack analysis showed that the blockage was able to reform when re-heated and tracked the thermal front. Moreover, the rate of blockage formation was observed to be slower when the LCST of the injected particles was higher. Our investigation is expected to pave the way for the design of "smart" and versatile polymer technologies for EOR applications in future studies.

Temperature-Responsive Polymer Brush Coatings for Advanced Biomedical Applications

Modern biomedical technologies predict the application of materials and devices that not only can comply effectively with specific requirements, but also enable remote control of their functions. One of the most prospective materials for these advanced biomedical applications are materials based on temperature-responsive polymer brush coatings (TRPBCs). In this review, methods for the fabrication and characterization of TRPBCs are summarized, and possibilities for their application, as well as the advantages and disadvantages of the TRPBCs, are presented in detail. Special attention is paid to the mechanisms of thermo-responsibility of the TRPBCs. Applications of TRPBCs for temperature-switchable bacteria killing, temperature-controlled protein adsorption, cell culture, and temperature-controlled adhesion/detachment of cells and tissues are considered. The specific criteria required for the desired biomedical applications of TRPBCs are presented and discussed.

Functional Thermoresponsive Hydrogel Molecule to Material Design for Biomedical Applications

Temperature-induced, rapid changes in the viscosity and reproducible 3-D structure formation makes thermos-sensitive hydrogels an ideal delivery system to act as a cell scaffold or a drug reservoir. Moreover, the hydrogels’ minimum invasiveness, high biocompatibility, and facile elimination from the body have gathered a lot of attention from researchers. This review article attempts to present a complete picture of the exhaustive arena, including the synthesis, mechanism, and biomedical applications of thermosensitive hydrogels. A special section on intellectual property and marketed products tries to shed some light on the commercial potential of thermosensitive hydrogels.

Control of Stimuli Sensitivity in pH-Switchable LCST/UCST-Type Thermosensitive Dendrimers by Changing the Dendrimer Structure

Stimuli-sensitive materials, such as pH- and temperature-responsive polymers, are useful as smart materials. Phenylalanine (Phe)-modified polyamidoamine (PAMAM) dendrimers with succinic acid termini, PAMAM-Phe-Suc, have been reported as unique pH-switchable lower critical solution temperature (LCST)-/upper critical solution temperature (UCST)-type thermosensitive polymers. Regulating the phase transition behavior of dendrimers is important for their applications. This study investigated the relationship between the dendrimer structure and stimuli sensitivity. Phe-modified PAMAM dendrimers with cyclohexanedicarboxylate termini (PAMAM-Phe-CHex) and sulfonate termini (PAMAM-Phe-SO₃Na) were synthesized. The temperature-dependent transmittance of these aqueous dendrimer solutions was examined at various pH values. PAMAM-Phe-CHex with Phe at all termini (PAMAM-Phe64-CHex) demonstrated a broad UCST-like phase transition at pH 7.0 but lacked an LCST-type phase transition. PAMAM-Phe-CHex with ≤ 27 Phe residues showed both LCST- and UCST-like phase transitions at different pH values, but the phase transition was broad. PAMAM-Phe-SO₃Na showed both LCST- and UCST-type phase transitions at different pH values, and the transition temperature increased as the bound Phe number decreased. Thus, the phase transition behavior of PAMAM-Phe-SO₃Na dendrimers can be regulated by varying the Phe/PAMAM ratios.

Temperature dependent single-chain structure of poly[3-(acrylamidopropyl-dimethyl-ammonium) propyl-1-sulfonate] via small-angle neutron scattering

Responsive polyzwitterionic materials have become important for a range of applications such as environmental remediation and targeted drug delivery. Much is known about the macroscopic phase-behaviors of such materials, but how the smaller scale single-chain structures of polyzwitterions respond to external stimuli is not well understood, especially at temperatures close to their phase boundaries. Such chain conformation responses are important in directing larger-scale associative properties. Here, we study the temperature dependent single-chain structure of a model polysulfobetaine, poly[3-(acrylamidopropyl-dimethyl-ammonium) propyl-1-sulfonate], using small angle neutron scattering. In the absence of salt, we find that temperature has a large effect on solvent quality with a decreasing trend from good solvent conditions at 50 °C to poor solvent at 10 °C (a temperature just above the cloud point of 7.6 °C) and an estimated theta temperature of 39 °C. When 100 mM NaCl is present, the solvent quality is good with weak temperature dependence. Without salt present, the polymer chain appears to have a nearly Gaussian coil conformation and the backbone becomes slightly more rigid as the temperature is lowered to the cloud point as determined by the Debye-local rod model on a Kratky plot. The addition of salt has a notable effect on the intra-chain correlations where an increase in chain dimensions to a swollen coil conformation and an increase in chain rigidity is observed at 100 mM NaCl in D2O, however, with a negligible temperature dependence.

UCST-Type Polymer Capsules Formed by Interfacial Complexation

Formation of aqueous-core polymer capsules exhibiting an upper critical solution temperature (UCST) was achieved using surfactant-polymer interfacial complexation in water-in-oil inverse emulsions. In fluorinated oil, Coulombic interactions between Krytox, an anionic oil-soluble surfactant, and a cationic poly(lysine) grafted with poly(acrylamide-co-acrylonitrile) enabled the formation of an adsorbed polymer shell at the surface of water droplets. The thermoresponsiveness of the polymer shell was assessed by fluorescence microscopy with and without the presence of nanoparticles, including gold particles. We show that, above the cloud point, polymers with a balanced fraction of UCST grafts form flat adlayers that (i) spontaneously entrap nanoparticles upon cooling and (ii) switch from fluid-like dynamics at high temperature to solid-like dynamics below the cloud point. This system offers a straightforward mean to prepare temperature-sensitive capsules in mild, biocompatible conditions and to concentrate nanoparticles (including nanoheaters) in their shell.

Phase Separation of Aqueous Poly(diisopropylaminoethyl methacrylate) upon Heating

Poly(diisopropylaminoethyl methacrylate) (PDPA) is a pH- and thermally responsive water-soluble polymer. This study deepens the understanding of its phase separation behavior upon heating. Phase separation upon heating was investigated in salt solutions of varying pH and ionic strength. The effect of the counterion on the phase transition upon heating is clearly demonstrated for chloride-, phosphate-, and citrate-anions. Phase separation did not occur in pure water. The buffer solutions exhibited similar cloud points, but phase separation occurred in different pH ranges and with different mechanisms. The solution behavior of a block copolymer comprising poly(dimethylaminoethyl methacrylate) (PDMAEMA) and PDPA was investigated. Since the PDMAEMA and PDPA blocks phase separate within different pH- and temperature ranges, the block copolymer forms micelle-like structures at high temperature or pH.

Polymeric Nanocomposites for Environmental and Industrial Applications

Polymeric nanocomposites (PNC) have an outstanding potential for various applications as the integrated structure of the PNCs exhibits properties that none of its component materials individually possess. Moreover, it is possible to fabricate PNCs into desired shapes and sizes, which would enable controlling their properties, such as their surface area, magnetic behavior, optical properties, and catalytic activity. The low cost and light weight of PNCs have further contributed to their potential in various environmental and industrial applications. Stimuli-responsive nanocomposites are a subgroup of PNCs having a minimum of one promising chemical and physical property that may be controlled by or follow a stimulus response. Such outstanding properties and behaviors have extended the scope of application of these nanocomposites. The present review discusses the various methods of preparation available for PNCs, including in situ synthesis, solution mixing, melt blending, and electrospinning. In addition, various environmental and industrial applications of PNCs, including those in the fields of water treatment, electromagnetic shielding in aerospace applications, sensor devices, and food packaging, are outlined.

Temperature-Transferable Coarse-Grained Model for Poly(propylene oxide) to Study Thermo-Responsive Behavior of Triblock Copolymers

Thermo-responsive behavior of ethylene oxide (EO)-propylene oxide (PO) copolymers makes them suitable for many potential applications. Reproducing the origins of the tunable properties of EO-PO copolymers using coarse-grained (CG) models such as the MARTINI force field is critically important for building a better understanding of their behavior. In the present work, we have investigated the effects of coarse-graining on the water-polymer interaction across a temperature range. We compared the performance of different all-atom force fields to find the most appropriate one for the purpose of PO block parameterization in the MARTINI platform. We parameterized a CG temperature-dependent PO model based on the reproduction of the atomistic free energy of transfer of propylene oxide trimer from octane to water over a range of temperatures (20-60 °C) and compared the atomistic bond and angle distributions. Then, we used the model to study the effects of EO/PO ratio, molecular weight, and concentration on the thermo-responsive behavior of EO-PO copolymers in water. The results show an excellent agreement with experiments in different areas. Our temperature-dependent model reproduces (1) micellar phase above critical micelle temperature (CMT) and unimer phase below CMT for different Pluronics (a class of EO-PO triblock copolymers) spanning many EO/PO ratios and molecular weights; (2) spherical-to-rodlike micellar shape transition for Pluronics with 60 wt % of PO content or more; (3) diffusion coefficients for Pluronics with high PO content (P104 Pluronic with a PO mass of 3500 g mol^-1) across a broad range of temperatures; and (4) micelle core size and micelle diameter similar to experimental results. Overall, our model improves the temperature sensitivity of EO-PO copolymers of existing models significantly, particularly for copolymers that are dominated by PO agents.

Sulfobetaine polymers for effective permeability into multicellular tumor spheroids (MCTSs)

Multicellular tumor spheroids (MCTSs) are attractive for drug screening before animal tests because they emulate an in vivo microenvironment. The permeability of the MCTSs and tumor tissues towards the candidate drugs is not sufficient even though the drugs can penetrate monolayer cultured cells; therefore, nanocarriers are required to enhance permeability and deliver drugs. In this study, we prepared zwitterionic polymers of sulfobetaine methacrylates and (meth)acrylamides with or without hydroxy groups between the zwitterions to serve as highly permeable nanocarriers. In the sulfobetaine polymers, poly(2-hydroxy-3-((3-methacrylamidopropyl)dimethylammonio)propane-1-sulfonate), P(OH-MAAmSB), the hydroxy group containing methacrylamide polymer exhibited little cytotoxicity and membrane translocation ability against monolayer cultured cells. Moreover, the excellent permeability of the hepatocyte MCTS enabled P(OH-MAAmSB) to permeate it and reach the center region (∼325 μm in diameter) at approximately 150 s, although poly(trimethyl-2-methacroyloxyethylammonium), a cationic polymer, penetrated just 1 to 2 layers from the periphery. The superior permeability of P(OH-MAAmSB) might be due to its good solubility and side chain conformation. P(OH-MAAmSB) is a promising nanocarrier with membrane translocation and permeability.

Dendronized Gelatins Showing Both LCST and UCST-type Thermoresponsive Behavior

Modification of natural polymers with stimuli-responsive synthetic moieties witnesses convergences of superior properties from natural polymers and stimuli-responsiveness to generate new intelligent materials. This was usally performed through synthetic polymers...

Nonionic star polymers with upper critical solution temperature in aqueous solutions

Novel UCST star poly(2-ureido methacrylates) synthesized via the ARGET ATRP technique showed enhanced trapping abilities of model drug molecules.

Functional polydiynes prepared by metathesis cyclopolymerization of 1,7-dihalogen-1,6-heptadiyne derivatives

The MCP route used for the polymerization of 1,6-heptadiynes was successfully applied to the polymerization of 1,7-dihalogen-1,6-heptadiynes, and the target polymers were obtained in high yield with high molecular weight and unique UCST behavior.

Water-soluble copolymers and their hydrogels with pH-tunable diverse thermoresponsive behaviors enabled by hydrogen bonding

Water-soluble copolymers display both UCST and LCST thermosensitivity in aqueous solution due to pH-determined hydrogen bonding between comonomer units, and their hydrogels can be used for information recording and encryption/decryption.

Synthesis of Betaine Copolymer for Surface Modification of Cotton Fabric by Enhancing Temperature-Sensitive and Anti-Protein Specific Absorption Performance

The growth and reproduction of microorganisms on fabrics could not only affect the wearability of textiles but also cause harm to human health, and it is an important problem that should be solved to reduce the adsorption and growth of microorganisms on the surface of the fabric. A series of ω-vinyl betaine copolymers were synthesized by catalytic chain transfer polymerization (CCTP) and were modified by mercapto-vinyl click chemistry to synthesize silane-modified betaine copolymers, which were used to treat the cotton fabric. The hydrophilic–hydrophobic transition performance and anti-protein specific adhesion performance of cotton fabric with the betaine copolymer were systematically investigated. The copolymer was confirmed to be successfully finished on the cotton fabric via ¹H–NMR and FTIR. The cotton fabric, which was treated by the betaine copolymer, presented temperature response performance in the range of 30–55 °C and had excellent anti-protein adsorption performance. The treated fabric had the best temperature-sensitive and anti-protein specific absorption performance among all the specimens when the mass fraction of G06B in DMAPS was 6 wt.%.