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Visualizing the network of a solvent-swollen polymer gel remains problematic. To address this challenge, open transmission electron microscopy (TEM) was applied to thin gel films permeated by a nonvolatile ionic liquid. The targeted physical gels were prepared by cooling concentrated solutions of poly(ethylene glycol) in 1-ethyl-3-methyl imidazolium ethyl sulfate [EMIM][EtSO4]. During the cooling, gelation occurred by a frustrated crystallization of the dissolved polymer, leading to a percolated, solvent-permeated semicrystalline network in which nanoscale polymer crystals acted as crosslinks. Crystalline features ranging from ~5 to ~200 nm were observed, with the visible network strands dominantly consisting of long curvilinear crystallites of ~15–20 nm diameter. Nascent spherulites irregularly decorated the network, creating a complex structural hierarchy that complicated analyses. Lacking diffraction contrast, TEM did not visualize the many disordered, fully solvated PEG chains present in the voids between crystals. Recognizing that a network's three dimensionality is ambiguous when assessed through two-dimensional microscopy projections, a small gel region was studied by TEM tomography, revealing a nearly isotropic three-dimensional arrangement of the curvilinear crystallites, which displayed remarkably uniform cylindrical cross sections.

The progress in polymer science and nanotechnology yields new colloidal and macromolecular objects and their combinations, which can be defined as complex polymer materials. The complexity may include a complicated composition and architecture of macromolecular chains, specific intermolecular interactions, an unusual phase behavior, and a structure of a multi-component polymer-containing material. Determination of a relation between the structure of a complex material, the structure and properties of its constituent elements, and the rheological properties of the material as a whole is the subject of structural rheology—a valuable tool for the development and study of novel materials. This work summarizes the author's structural–rheological studies of complex polymer materials for determining the conditions and rheo-manifestations of their micro- and nanostructuring. The complicated chemical composition of macromolecular chains and its role in polymer structuring via block segregation and cooperative hydrogen bonds in melt and solutions is considered using tri- and multiblock styrene/isoprene and vinyl acetate/vinyl alcohol copolymers. Specific molecular interactions are analyzed in solutions of cellulose; its acetate butyrate; a gelatin/carrageenan combination; and different acrylonitrile, oxadiazole, and benzimidazole copolymers. A homogeneous structuring may result from a conformational transition, a mesophase formation, or a macromolecular association caused by a complex chain composition or specific inter- and supramolecular interactions, which, however, may be masked by macromolecular entanglements when determining a rheological behavior. A heterogeneous structure formation implies a microscopic phase separation upon non-solvent addition, temperature change, or intense shear up to a macroscopic decomposition. Specific polymer/particle interactions have been examined using polyethylene oxide solutions, polyisobutylene melts, and cellulose gels containing solid particles of different nature, demonstrating the competition of macromolecular entanglements, interparticle interactions, and adsorption polymer/particle bonds in governing the rheological properties. Complex chain architecture has been considered using long-chain branched polybutylene-adipate-terephthalate and polyethylene melts, cross-linked sodium hyaluronate hydrogels, asphaltene solutions, and linear/highly-branched polydimethylsiloxane blends, showing that branching raises the viscosity and elasticity and can result in limited miscibility with linear isomonomer chains. Finally, some examples of composite adhesives, membranes, and greases as structured polymeric functional materials have been presented with the demonstration of the relation between their rheological and performance properties. [ABSTRACT FROM AUTHOR]

Biological materials always exhibit heterogeneous physical properties, both mechanical and chemical, which give them a rich phenomenology that poses significant challenges in the developing of effective models. The Flory–Rehner theory revolutionized our understanding of the dynamics of the liquid-polymers coupling in soft swollen gels, recognizing polymers as elastic networks stretched by the presence of liquid. Despite its foundational role, applying this theory to bodies with non uniform physical properties requires further improvements. This article proposes a unified approach to address mechano-diffusion challenges in multi-domain bodies, that is in material bodies made of regions having different chemo-mechanical properties, and focuses on the dehydration and remodeling of biological-like materials. Drawing inspiration from natural systems, we integrate principles from nonlinear mechanics and swelling theories; in particular, what is specifically new is the idea of applying the notion of the multiplicative decomposition of the strain–developed for plasticity–to model the swelling properties of a body made of two or more materials. The article gives a systematic presentation of the subject, and guides readers through key concepts and practical insights, aiming to provide a robust framework for modeling chemo-mechanical interactions. Moreover, it paves the way for the modeling of heterogenous bodies having spatially-varying properties. [ABSTRACT FROM AUTHOR]

A systematic study has been performed for the effect of nonionic surfactants (NSs), i.e., ethoxylated higher fatty alcohols with different ethoxylation degrees, on the ultrasonic dispersion of carbon nanotubes in aqueous solutions and on the colloid-chemical properties of the resulting dispersions, namely, their optical density and the sizes and electrokinetic potentials of the particles in the colloidal systems. A non-linear dependence of the characteristics of dispersions on the ethoxylation degree has been revealed. This dependence is associated with structural transformations in NS molecules. The most efficient ethoxylation degree and concentration of nonionic surfactants in a solution, which have the highest disaggregating and stabilizing effects upon the preparation of carbon nanotube (CNT) dispersions, have been determined. The influence of the ethoxylation degree of the ethoxylated higher fatty alcohols on the electrokinetic properties of CNT dispersions has been revealed. It has been shown that carbon nanotube dispersions can be used to modify the rheological and electrical properties of gel systems based on rarely crosslinked poly(acrylic acid). The effects of NSs and CNTs on the viscosity, shear yield stress, consistency index, mechanical stability, relaxation time, and viscous flow activation energy of the polymer gels have been studied. It has been shown that the incorporation of nanotubes increases the electrical conductivity of the gels. The ultrastructure of the gel samples has been studied by transmission electron microscopy. [ABSTRACT FROM AUTHOR]

Large scale computer simulations are employed to analyze the conformations of network strands in polymer networks at preparation conditions (characterized by a polymer volume fraction of ϕ0) and when swollen to equilibrium (characterized by a polymer volume fraction ϕ < ϕ0). Network strands in end‐linked model networks are weakly stretched and partially swollen at preparation conditions as compared to linear polymers in the same solvent at ϕ0. Equilibrium swelling causes non‐ideal chain conformations characterized by an effective scaling exponent approaching 7/10 on intermediate length scales for increasing overlap of the chains. The chain size in a network consists of a fluctuating and a time average "elastic" contribution. The elastic contribution swells essentially affinely ∝(ϕ0/ϕ)2/3, whereas the swelling of the fluctuating part lies between the expected swelling of the entanglement constraints and the swelling of non‐cross‐linked chains in a comparable semi‐dilute solution. The total swelling of chain size results from the changes of both fluctuating and non‐fluctuating contributions. [ABSTRACT FROM AUTHOR]

Ionic conductive hydrogel has recently garnered significant research attention due to its potential applications in the field of wearable and flexible electronics. Nonetheless, the integration of multifunctional and synergistic advantages, including reliable electronic properties, high swelling capacity, exceptional mechanical characteristics, and self-adhesive properties, presents an ongoing challenge. In this study, we have developed an ionic conductive hydrogel through the co-polymerization of 4-Acryloylmorpholine (ACMO) and sodium acrylate using UV curing technology. The hydrogel exhibits excellent mechanical properties, high conductivity, superior swelling capacity, and remarkable self-adhesive attributes. The hydrogel serves as a highly sensitive strain sensor, enabling precise monitoring of both substantial and subtle human motions. Furthermore, the hydrogel demonstrates the capability to adhere to human skin, functioning as a human-machine interface for the detection of physiological signals, including electromyogram (EMG) signals, with low interfacial impedance. This work is anticipated to yield a new class of stretchable and conductive materials with diverse potential applications, ranging from flexible sensors and wearable bio-electronics to contributions in the field of artificial intelligence.

Polymer-based hydrogels are hydrophilic polymer networks with a remarkable capacity to absorb substantial amounts of water and biological fluids, rendering them highly attractive for drug delivery applications. The COVID-19 pandemic has acted as a catalyst for research and innovation in the realm of polymer-based hydrogels for drug delivery, with a particular emphasis on antiviral therapeutics, vaccines, diagnostics, and precision delivery to the respiratory system. The distinctive attributes of hydrogels, such as their biocompatibility, customizable drug release profiles, and ease of functionalization, establish them as versatile platforms for the development of advanced drug delivery systems to combat not only COVID-19 but also a spectrum of other infectious diseases. This study is dedicated to scruti-nizing and evaluating the characteristics of polymer-based hydrogels employed in drug delivery for the treatment of diseases associated with the SARS-CoV-2 virus. Furthermore, the investigation introduces a novel classification system for polymer-based hydrogels deployed in drug delivery for SARS-CoV-2-related diseases. Additionally, the paper provides an up-to-date evaluation of the latest developed hydrogels utilized in drug delivery for the treatment of dis-eases linked to the SARS-CoV-2 virus, based on research conducted through the recent months of 2023.

Adhesives have been widely applied in various fields. However, most industrial adhesives contain organic solvents, which are toxic and difficult to clean after use. Importantly, most adhesives are used in a relatively small temperature range (0–50 °C), which is due to the fragmentation of the morphology and properties of supramolecular polymer gels at low temperatures. Most of the supramolecular adhesives need to be heated during the bonding process, which cannot meet the requirements of low-temperature adhesion in daily life and industry. In this study, based on the concept of using deep eutectic solvents (DESs) as a platform, cyclodextrin (β-CD) and carboxyl terminated hyperbranched polyester (DCHP) were used to prepare solvent-free supramolecular polymer gel (CD-DCHP), which was non-toxic and easy to clean. Due to the joint action of deep eutectic solvent and supramolecular polymer structure, CD-DCHP showed excellent mechanical properties, super strong adhesion (up to 4.55 MPa on glass surface), and excellent low-temperature performance (up to 1.64 MPa at –60 °C). This supramolecular polymer gel also showed excellent tolerance to acids, alkalis, and various organic solvents. It greatly expanded the application of DES and provided a new approach to the development of supramolecular adhesives.

Today, a significant part of production wells' stock has a high water cut percentage of 90% and above. Obviously, for this reason, the need to develop new and improved existing technologies for water shut-off in wells increases every year. Physico-chemical methods of water shut-off are based on the application of special reagents and compositions that plug the pathways of water inflow to the well. Depending on the mechanism and specific features of water barrier formation, isolation methods are divided into selective and non-selective. This article investigates the possibility of using hydrolyzed polyacrylonitrile as a gel-forming and precipitation-forming reagent for water shut-off technologies in production wells. A surfactant–polymer composition for the isolation of water inflow in production wells in objects with high salinity in formation water, possessing physical and chemical selectivity and providing permeability reduction only in water-saturated intervals, is proposed. The developed composition is the invert emulsion, which makes it possible to carry out treatment at a distance from the well and solve the problem of possible premature gel formation directly in the wellbore. The lowest effective concentration of HPAN in an aqueous solution for use as a gel-forming and sedimentation reagent was determined experimentally (5.0 wt% and more). The interaction of the polymer solution with a chromium crosslinker allows obtaining structured gels in the whole volume of the system. The structure of the gels was evaluated using the Sydansk classifier with the assignment of a letter code from A to J. It was experimentally proved that the structure of the obtained gels depends on the temperature and content of the crosslinking agent in the system; the more crosslinking agent in the composition of the system, the stronger the structure of the resulting gel. The optimal ratio of polymer and crosslinking agent to obtain a strong gel was obtained, which amounted to 5:1 by weight of dry polymer powder. For the HPAN concentration of 5 wt% according to the Sydansk classifier, the gel structure had the code "H"—slightly deformable non-flowing gel. The dependence of the volume of gel sediment obtained because of the interaction with mineralized water on the polymer concentration was studied. It was proved that an increase in the concentration of hydrolyzed polyacrylonitrile in the solution, as well as an increase in the concentration of calcium ions in mineralized water, leads to a larger volume of the resulting gel or precipitate and to the strengthening of the gel structure. The results of rheological studies of the developed composition, as well as experiments on thermal stability, are presented. The results of filtration tests on bulk reservoir models demonstrated the selectivity of the developed composition. The obtained value of the residual resistance factor for the oil-saturated low-permeability model was 1.49 units; the value of the residual resistance factor for the water-saturated high-permeability model was 18.04 units. The ratio of the obtained values of the residual resistance factor, equal to 0.08 (much less than 1), can characterize the developed composition as a selective material for water shut-off in producing wells. Existing technologies for water shut-off based on HPAN do not allow for making a treatment at a distance from the well and require the use of technological solutions to prevent premature gel sedimentation in the well. The developed composition makes it possible to solve the problem of premature gelation. In addition, the composition can form a blocking screen in highly permeable water-saturated zones. The development can be useful for deposits with difficult conditions (high mineralization in reservoir waters, boreholes with a horizontal end, elevated temperatures up to 80 °C). [ABSTRACT FROM AUTHOR]

As an important category of smart materials, stimuli-responsive hydrogels are highly concerned due to their extensive application possibilities and their outstanding biocompatibilities. The ability of responsive hydrogels about significant volume change by external stimuli inspires the design of electronic devices, for example, as sensors and actuators. The modeling of the hydrogel behavior enables the optimization of corresponding applications. In the present research, on the basis of the experimentally determined material parameters, a chemo-poromechanical model was implemented in COMSOL Multiphysics® to investigate the constricted swelling of hydrogels. The swelling kinetics affected by the diffusion coefficient is discussed in detail with numerical simulations. [ABSTRACT FROM AUTHOR]

Polymer gels are an important class of soft materials with growing interest for biomedical applications due to their distinctive properties. These three‐dimensional polymer networks are capable of imbibing large amounts of solvent while maintaining solid‐like behavior. Polymer gels can be classified into hydrogels, aerogels, and cryogels based on their structural features. Their highly porous structure, swelling capacity, and biocompatibility make them well‐suited for diverse uses in biomedicine. Recent advances have enabled the engineering of polymer gels with tunable architectures and smart functionality responsive to stimuli. These developments have expanded the potential of gels in areas like tissue engineering, drug delivery, wound healing, and biosensing. However, the toxicity of polymer gels remains an important consideration for biomedical use. Careful design and toxicological evaluation is essential to ensure safe clinical application. Overall, polymer gels offer new possibilities in biomedicine through continued research on synthesizing biocompatible gels and elucidating structure–function relationships. This review provides an updated perspective on the progress and promise of tailoring polymer gels to advance biomedicine, while also considering the critical aspect of biocompatibility. [ABSTRACT FROM AUTHOR]

The progress in polymer science and nanotechnology yields new colloidal and macromolecular objects and their combinations, which can be defined as complex polymer materials. The complexity may include a complicated composition and architecture of macromolecular chains, specific intermolecular interactions, an unusual phase behavior, and a structure of a multi-component polymer-containing material. Determination of a relation between the structure of a complex material, the structure and properties of its constituent elements, and the rheological properties of the material as a whole is the subject of structural rheology—a valuable tool for the development and study of novel materials. This work summarizes the author’s structural–rheological studies of complex polymer materials for determining the conditions and rheo-manifestations of their micro- and nanostructuring. The complicated chemical composition of macromolecular chains and its role in polymer structuring via block segregation and cooperative hydrogen bonds in melt and solutions is considered using tri- and multiblock styrene/isoprene and vinyl acetate/vinyl alcohol copolymers. Specific molecular interactions are analyzed in solutions of cellulose; its acetate butyrate; a gelatin/carrageenan combination; and different acrylonitrile, oxadiazole, and benzimidazole copolymers. A homogeneous structuring may result from a conformational transition, a mesophase formation, or a macromolecular association caused by a complex chain composition or specific inter- and supramolecular interactions, which, however, may be masked by macromolecular entanglements when determining a rheological behavior. A heterogeneous structure formation implies a microscopic phase separation upon non-solvent addition, temperature change, or intense shear up to a macroscopic decomposition. Specific polymer/particle interactions have been examined using polyethylene oxide solutions, polyisobutylene melts, and cellulose gels containing solid particles of different nature, demonstrating the competition of macromolecular entanglements, interparticle interactions, and adsorption polymer/particle bonds in governing the rheological properties. Complex chain architecture has been considered using long-chain branched polybutylene-adipate-terephthalate and polyethylene melts, cross-linked sodium hyaluronate hydrogels, asphaltene solutions, and linear/highly-branched polydimethylsiloxane blends, showing that branching raises the viscosity and elasticity and can result in limited miscibility with linear isomonomer chains. Finally, some examples of composite adhesives, membranes, and greases as structured polymeric functional materials have been presented with the demonstration of the relation between their rheological and performance properties.

Poly(3-hydroxybutyrate) (PHB), a bio-produced and biodegradable polymer, has great potential as a replacement for petroleum-based polymers in many applications. However, strategies for the extraction and processing of PHB still require improvement. Switchable solvents, which can be toggled between hydrophobic and hydrophilic forms by the addition or removal of carbon dioxide in the presence of water, are easily recyclable and may improve PHB processing methods. Here, we have shown the ability to dissolve PHB in two switchable solvents (N,N-dimethylbenzylamine and N,N-dimethylcyclohexylamine), precipitate PHB by the addition of water and carbon dioxide, and recycle the solvent for subsequent dissolution and precipitation cycles. We have also demonstrated the ability for N,N-dimethylbenzylamine to form gels with PHB which maintain their water/solvent content as the solvent is switched to a hydrophilic form. These results demonstrate the usefulness of switchable solvents as a recyclable platform for PHB processing and their ability to create unique materials.

Hydrogel adhesion that can be easily modulated in magnitude, space, and time is desirable in many emerging applications ranging from tissue engineering and soft robotics to wearable devices. In synthetic materials, these complex adhesion behaviors are often achieved individually with mechanisms and apparatus that are difficult to integrate. Here, we report a universal strategy to embody multifaceted adhesion programmability in synthetic hydrogels. By designing the surface network topology of a hydrogel, supramolecular linkages that result in contrasting adhesion behaviors are formed on the hydrogel interface. The incorporation of different topological linkages leads to dynamically tunable adhesion with high-resolution spatial programmability without alteration of bulk mechanics and chemistry. Further, the association of linkages enables stable and tunable adhesion kinetics that can be tailored to suit different applications. We rationalize the physics of polymer chain slippage, rupture, and diffusion at play in the emergence of the programmable behaviors. With the understanding, we design and fabricate various soft devices such as smart wound patches, fluidic channels, drug-eluting devices, and reconfigurable soft robotics. Our study presents a simple and robust platform in which adhesion controllability in multiple aspects can be easily integrated into a single design of a hydrogel network. [ABSTRACT FROM AUTHOR]

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There is a considerable body of work that describes the scaling of diblock copolymer micelle dimensions in dilute and semi‐dilute solution based upon block degrees of polymerization and copolymer concentration. However, there is a lack of analogous information for semi‐dilute ABA triblock copolymer gels, which consist of ABA triblock copolymer dissolved in midblock‐selective (B‐selective) solvent. The present study uses small angle X‐ray scattering to extract micelle dimensions for numerous triblock copolymer gels that vary in copolymer identity (and hence block lengths) and copolymer concentration, as well as gels that contain various ratios of two unique triblock copolymers. Analysis of micelle structural data subsequently translates to universal scaling expressions for the micelle core radius – rA ≈ NA0.53NB−0.14ϕABA0.16 where NA and NB are the endblock and midblock degrees of polymerization, respectively, and ϕABA is the volume fraction of triblock copolymer in the gel – and for the intermicelle spacing – lAA ≈ NA0.09NB0.29ϕABA−0.35. Each scaling expression describes the full collection of experimental data very well. Additionally, these scaling expressions are partially in line with expectations from semi‐dilute diblock copolymer solution theory. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the influence of the surface/volume granule ratio of amaranth, corn, and potato starches on the rheological properties of pastes and gels obtained at 5 and 10% solids concentration through granulometry, scanning electron microscopy, rotational, and dynamic rheological measurements. The granule size distribution and the surface/volume ratio drove the rheological behaviour as a function of temperature and concentration. At a concentration of 10%, the consistency index of corn starch (CS) paste was 147.25 Pa.sn (n - flow behavior index), a higher value compared to pastes from potato starch (PS), 86.54 Pa.sn, and amaranth starch (AS), 44.48 Pa.sn. The lowest values of the loss angle tangent (Tan δ) in CS (0.052 and 0.035) at both solids concentrations suggested a better gel conformation. Noticeable changes in consistency index and storage modulus were observed in CS. A theoretical analysis of the surface/volume ratio change showed that CS reached a 2.2 value, much lower than the 4.5 and 5.8 values for PS and AS, respectively. These findings provide additional criteria for the food industry when choosing starches with suitable rheological behaviour as a function of surface/volume granule ratio and solids concentration.

Today, a significant part of production wells’ stock has a high water cut percentage of 90% and above. Obviously, for this reason, the need to develop new and improved existing technologies for water shut-off in wells increases every year. Physico-chemical methods of water shut-off are based on the application of special reagents and compositions that plug the pathways of water inflow to the well. Depending on the mechanism and specific features of water barrier formation, isolation methods are divided into selective and non-selective. This article investigates the possibility of using hydrolyzed polyacrylonitrile as a gel-forming and precipitation-forming reagent for water shut-off technologies in production wells. A surfactant–polymer composition for the isolation of water inflow in production wells in objects with high salinity in formation water, possessing physical and chemical selectivity and providing permeability reduction only in water-saturated intervals, is proposed. The developed composition is the invert emulsion, which makes it possible to carry out treatment at a distance from the well and solve the problem of possible premature gel formation directly in the wellbore. The lowest effective concentration of HPAN in an aqueous solution for use as a gel-forming and sedimentation reagent was determined experimentally (5.0 wt% and more). The interaction of the polymer solution with a chromium crosslinker allows obtaining structured gels in the whole volume of the system. The structure of the gels was evaluated using the Sydansk classifier with the assignment of a letter code from A to J. It was experimentally proved that the structure of the obtained gels depends on the temperature and content of the crosslinking agent in the system; the more crosslinking agent in the composition of the system, the stronger the structure of the resulting gel. The optimal ratio of polymer and crosslinking agent to obtain a strong gel was obtained, which amounted to 5:1 by weight of dry polymer powder. For the HPAN concentration of 5 wt% according to the Sydansk classifier, the gel structure had the code “H”—slightly deformable non-flowing gel. The dependence of the volume of gel sediment obtained because of the interaction with mineralized water on the polymer concentration was studied. It was proved that an increase in the concentration of hydrolyzed polyacrylonitrile in the solution, as well as an increase in the concentration of calcium ions in mineralized water, leads to a larger volume of the resulting gel or precipitate and to the strengthening of the gel structure. The results of rheological studies of the developed composition, as well as experiments on thermal stability, are presented. The results of filtration tests on bulk reservoir models demonstrated the selectivity of the developed composition. The obtained value of the residual resistance factor for the oil-saturated low-permeability model was 1.49 units; the value of the residual resistance factor for the water-saturated high-permeability model was 18.04 units. The ratio of the obtained values of the residual resistance factor, equal to 0.08 (much less than 1), can characterize the developed composition as a selective material for water shut-off in producing wells. Existing technologies for water shut-off based on HPAN do not allow for making a treatment at a distance from the well and require the use of technological solutions to prevent premature gel sedimentation in the well. The developed composition makes it possible to solve the problem of premature gelation. In addition, the composition can form a blocking screen in highly permeable water-saturated zones. The development can be useful for deposits with difficult conditions (high mineralization in reservoir waters, boreholes with a horizontal end, elevated temperatures up to 80 °C).

Polymer gels are a valuable class of polymeric materials that have recently attracted significant interest due to the exceptional properties such as versatility, soft-structure, flexibility and stimuli-responsive, biodegradability, and biocompatibility. Based on their properties, polymer gels can be used in a wide range of applications: food industry, agriculture, biomedical, and biosensors. The utilization of polymer gels in different medical and industrial applications requires a better understanding of the formation process, the factors which affect the gel's stability, and the structure-rheological properties relationship. The present review aims to give an overview of the polymer gels, the classification of polymer gels' materials to highlight their important features, and the recent development in biomedical applications. Several perspectives on future advancement of polymer hydrogel are offered. [ABSTRACT FROM AUTHOR]

This article studies the structural and mechanical properties of polymer hydrogels based on polyelectrolyte complexes of N-succinyl-chitosan (NSC) with poly-N,N-diallyl-N,N-dimethylammonium chloride, depending on the composition of the reaction mixture and the conditions for obtaining complexes. The types of intermolecular interaction between the components of the complexes are studied by IR spectroscopy. The causes of swelling of coacervates based on polyelectrolyte complexes of N-succinylchitosan-chitosan with poly-N,N-diallyl-N,N-dimethylammonium chloride are analyzed. The relationship between the composition of coacervates and the structural-mechanical and transport properties of the gels formed from them is established. The developed approach to create elastic-viscous systems can be implemented when creating gel-like polymeric materials capable of self-organization into systems with controlled characteristics of the structure. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the influence of the surface/volume granule ratio of amaranth, corn, and potato starches on the rheological properties of pastes and gels obtained at 5 and 10% solids concentration through granulometry, scanning electron microscopy, rotational, and dynamic rheological measurements. The granule size distribution and the surface/volume ratio drove the rheological behaviour as a function of temperature and concentration. At a concentration of 10%, the consistency index of corn starch (CS) paste was 147.25 Pa·sn (n - flow behavior index), a higher value compared to pastes from potato starch (PS), 86.54 Pa·sn, and amaranth starch (AS), 44.48 Pa·sn. The lowest values of the loss angle tangent (Tan d) in CS (0.052 and 0.035) at both solids concentrations suggested a better gel conformation. Noticeable changes in consistency index and storage modulus were observed in CS. A theoretical analysis of the surface/volume ratio change showed that CS reached a 2.2 value, much lower than the 4.5 and 5.8 values for PS and AS, respectively. These findings provide additional criteria for the food industry when choosing starches with suitable rheological behaviour as a function of surface/volume granule ratio and solids concentration. [ABSTRACT FROM AUTHOR]

The wide range of hydrogel applications is a result of the optimization of gelation. Herein, the various aminooxylinkers were synthesized to study the kinetics of gelation and mechanical properties of hydrogels prepared by crosslinking of aldehyde-modified N-acetylglucosamine (GlcNAc) of hyaluronan (ΔHA-CHO: 4,5-anhydro-6-(GlcNAc)-oxo hyaluronan or HA-CHO: 6-(GlcNAc)-oxo hyaluronan). Structural characteristics of the linkers (length, number of functional groups and rigidity) and the polymer (effect of the –C=C- double bond) were investigated in detail and showed decreasing mechanical stiffness with increasing hydrophobic character of linker and effect of its rigidity/flexibility on imine conversion. Besides known linear bis(aminooxy)alkanes with different lengths of the chain, new multifunctional aminooxy-linkers: 1,3,5-tris(aminooxymethyl)benzene and multikis(6-aminooxy-6-deoxy)-β-cyclodextrin were prepared and shortened the gelation time. The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) analysis showed that despite the aminooxylinkers ´ cytotoxicity at higher concentrations, the final oxime hydrogels are non-cytotoxic and therefore are suitable for medicinal applications.

Dynamic light scattering (DLS) is a rich source of information in investigations of the frequency response of soft materials. Most commonly, however, it is underemployed, mainly for determining the size of suspended particles or macromolecules in solution. This article emphasizes some of the other aspects of the technique, how it acts as a frequency discriminator between mechanisms of differing relaxation rates, and how it can be used to determine directly the thermodynamic properties not only of simple solutions, but also of polymer gels and inhomogeneous solutions, as well as their large-scale structure. The method is illustrated with several detailed examples. [ABSTRACT FROM AUTHOR]

As advanced radiotherapy techniques progress to deliver a high absorbed dose to the target volume while minimizing the dose to normal tissues using intensity-modulated beams, arcs or stereotactic radiosurgery, new challenges occur to assure that the high treatment dose is delivered homogeneously to the tumor. Small irradiation field sizes (≤1 cm2) that tightly conform to precise target regions and allow for the deliverance of doses with a high therapeutic ratio, are of particular interest. However, the small field dosimetry using conventional dosimeters is limited by the relative large size of the detector. Radiation-sensitive polymer gels have the potential to meet this dosimetry challenge due to their almost unlimited ability in resolving three-dimensional dose distributions of any shape and makes them unique and suitable for the evaluation of dose profiles and the verification of complex doses. In this work, dose distributions in nMAG gels that have been irradiated to different doses by applying a 6 MV FFF photon beam collimated to 1 cm2, were analyzed and the dose profiles were evaluated by applying a gamma passing rate criteria of 3%/3 mm and considering different post-irradiation time intervals between the irradiation and the gels read out process. X-ray CT and NMR imaging procedures were used for the dose evaluation. It was found that the shape and uniformity of the dose profiles were changing due to post-irradiation polymerization and gelation processes, indicating time dependent growing uniformity which was better expressed for the higher delivered doses. It was estimated that in order to obtain acceptably symmetric small field dose profiles, a longer post-irradiation time is needed for getting the full scope of the polymerization as compared with the recently recommended 24 h period between irradiation and the read out processes of the dose gels. An estimated overall uncertainty (double standard deviation, 95% confidence level) of 3.66% was achieved by applying R2 measurements (NMR read out), and a 3.81–applying X-ray CT read out for 12 Gy irradiated gels 56 h post-irradiation. An increasing tendency for the uncertainty was observed with a decreasing post-irradiation time. A gamma passing rate of 90.3% was estimated for the 12 Gy irradiated gels and, 56 h post-irradiation, the X-ray CT evaluated gels as well as a gamma passing rate of 92.7% was obtained for the NMR evaluated gels applying a 3%/3 mm passing criteria. [ABSTRACT FROM AUTHOR]

Out-of-plane curvature is an important, but poorly explored geometric parameter that influences cell behavior. We address the impact of curvature on epithelial proliferation through monitoring how MDCK cells proliferate on planar and curved toroidal hydrogel substrates with a broad range of Gaussian curvatures. We illustrate in detail the imaging processing methodology to characterize curved surfaces and quantify proliferation of cells. We find that MDCK cells grow readily on both curved and flat surfaces and can cover the entire surface of the toroidal structure as long as the initial seeding is uniform. Our analysis shows that proliferation does not depend on Gaussian curvature within the range probed in our experiment, but rather on cell density. Despite epithelial proliferation is insensitive to the curvature range presented in this study, the toroidal-construct fabrication technique and image processing methodology may find utility for probing cell processes like collective migration, as it involves long-range force transmission.

Polymer gels have been widely used in the field for tissue engineering, sensing, and drug delivery due to their excellent biocompatibility, hydrophilicity, and degradability. However, common polymer gels are easily deformed on account of their relatively weak mechanical properties, thereby hindering their application fields, as well as shortening their service life. The incorporation of reversible non-covalent bonds is capable of improving the mechanical properties of polymer gels. Thus, here, a poly(methyl methacrylate) polymer network was prepared by introducing host–guest interactions between pillar[5]arene and pyridine cation. Owing to the incorporated host–guest interactions, the modified polymer gels exhibited extraordinary mechanical properties according to the results of the tensile tests. In addition, the influence of the host–guest interaction on the mechanical properties of the gels was also proved by rheological experiments and swelling experiments. [ABSTRACT FROM AUTHOR]

Based on the variational approach, boundary value problems are formulated that describe the state of thermodynamic equilibrium of polymer gels in the field of body forces. A polymer gel is considered as a mixture, which is an elastic material and a liquid (solvent) dissolved in it. The general theory is applied to study the deformation behavior of polymer gels and plasticized polymer materials in a gravity field. Within the framework of a model problem that describes the equilibrium state of a gel in the form of a flat layer, the conditions are established under which a solvent or plasticizer is capable of separating from a polymer under the action of gravity. In particular, relations were obtained that make it possible to estimate the critical values of the parameters at which the solvent is released, as well as to calculate the amount of liquid released from the material. [ABSTRACT FROM AUTHOR]

The recovery of crude oil and volatile organic compounds (VOCs) spilt in the environment is an intractable problem for environmental scientists. In this paper, a new lipophilic polyelectrolyte gel as an absorbent for various volatile chemical compounds is demonstrated. It is prepared by radical copolymerization of an acrylate monomer with an ionic group, tetraalkylammonium tetraarylborate, octadecyl acrylate, and a crosslinker, dipropylene glycol diacrylate, in the presence of a radial initiator. Investigation of the swelling behavior for the mixtures of water or aqueous salts reveals that the gel shows similar swelling behavior to those for pure organic solvents. On the other hand, the swelling degree in THF‐water mixture is lower than that of pure THF, because THF and water are miscible to each other, and the presence of a small amount of water in THF reduces the compatibility of the gel and THF. The salting‐out effect can separate the THF‐water mixture to form a biphasic system and recover the high swelling ability of the gel. The swelling behavior in the mixture of water‐organic solvents systems provides a new insight for designing VOC and oil absorbents in various environmental conditions, especially in hydrosphere such as seas and lakes. [ABSTRACT FROM AUTHOR]

Polymer hydrogels are a promising category of materials for conformance control of oil reservoirs. One of the main difficulties of this application is the severe temperature and salinity of many reservoirs. Nanotechnology is an alternative to improve the performance of gels, by enabling the insertion of reinforcement fillers in their composition, enhancing rheological properties, e.g., tan(delta) measurements. This study evaluated the properties of hydrogels based on partially hydrolyzed polyacrylamide (HPAM), with different molar masses, crosslinked with polyethyleneimine (PEI), with or without aluminum or zinc oxide. For simulation of one real reservoir characteristic, gelling systems were prepared with synthetic brine containing 29.940 mg/L of total dissolved solids (TDS) and aged at a temperature of 70 °C. The concentrations of 5000 mg/L of HPAM and 2200 mg/L of PEI were chosen to obtain nanocomposite hydrogels containing 50, 100, or 200 mg/L of oxides. The hydrogels were evaluated by means of the gel strength code, rheological tests, Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The results indicated that the best rheological properties were obtained by the nanocomposite hydrogels when compared to conventional hydrogels when aged at 70 °C. The viscous modulus/elastic modulus ratio (G″/G′) and tan(delta) factor indicated that the decrease of the elastic component began after 7 days for the conventional hydrogels and after 15 days for the nanocomposite hydrogels. The best filler concentration was 200 mg/L according to the tan(delta) values. The micrographs confirmed the presence of metal oxide particles in the polymer matrix, which possibly contributed to strengthening the structure of these materials. [ABSTRACT FROM AUTHOR]

Over the past decades, there has been a flourishing of phase-separated polymer gels. Unlike traditional design methods that rely on chemical structure and polymer network construction, phase separation enables polymers to tune morphologies across the microscopic, mesoscopic, and macroscopic levels, thereby creating a new path for regulating and innovating the performance of polymer gels. This comprehensive review offers a deep dive into the mechanisms underlying phase separation formation in polymer gels and makes a particular focus on the methods used to induce phase separation in polymer gels. Additionally, the review highlights the potential performance improvements and innovations of polymer gels based on phase separation and explores the promising applications of phase separation polymers in various fields. Finally, this review emphasizes the potential benefits yet significant challenges associated with phase-separated polymer gels. The versatility and multi-scale applicability of this approach make it a promising pathway for developing cutting-edge materials with tailored properties and functionalities. [Display omitted] [ABSTRACT FROM AUTHOR]

Within the framework of the variational approach, boundary value problems are formulated that describe the thermodynamically equilibrium states of statically loaded polymer gels and take into account the conditions of mass transfer of the material with the external environment. A polymer gel is considered as a system that is an elastic (highly elastic) material and a liquid dissolved in it. The liquid (solvent) is assumed to be non-volatile. It is shown that the behavior of the gel depends significantly on the medium in which it is deformed. In particular, when the gel is deformed in the atmosphere, the absorption of liquid by the material from the external environment is excluded; however, it is possible to squeeze out the liquid from the material (in the case of compressive loads). It is shown that such conditions of mass transfer, within the framework of the variational approach, are naturally formulated in the form of one-sided constraints in the form of inequalities. The general theory is illustrated by the example of describing the deformation behavior of polymer gels under conditions of uniaxial tension and compression in a solvent medium and in the atmosphere. [ABSTRACT FROM AUTHOR]

Responsive polymer materials possessing variable mechanical properties have shown promising practical applications, whereas water has clear advantages among the triggers owing to its wide abundance, green characteristics, as well as mild conditions involved. However, ubiquitous water‐induced softening would prevent polymer materials from applications with high humidity or aqueous environment. Herein, an unprecedented polymer gel material is reported that exhibits a dramatic and reversible water‐induced stiffening base on phase separation, differing from traditional ones that are usually weakened upon hydration due to the plasticizing effect. The material shows a large stiffness change in Young's modulus (as much as 104 times), which is much larger than that induced by glass transition and comparable to that caused by crystallization‐melting process. The polymer materials are fabricated in a facile way by introducing an ionic liquid and a lithium salt into a poly(benzyl methacrylate) network. Moreover, the volume remains almost unchanged during the reversible soft–stiff transition. A universal approach of water‐induced stiffening is proposed and verified on various systems. As for demonstration, this material is used for humidity‐induced shape memory. This work offers an effective method for developing water‐induced stiffened material and will pave the way toward potential applications for water‐responsive polymer materials. [ABSTRACT FROM AUTHOR]

The wide range of hydrogel applications is a result of the optimization of gelation. Herein, the various aminooxylinkers were synthesized to study the kinetics of gelation and mechanical properties of hydrogels prepared by crosslinking of aldehyde-modified N-acetylglucosamine (GlcNAc) of hyaluronan (?HA-CHO: 4,5-anhydro-6-(GlcNAc)-oxo hyaluronan or HA-CHO: 6-(GlcNAc)-oxo hyaluronan). Structural characteristics of the linkers (length, number of functional groups and rigidity) and the polymer (effect of the -C=C- double bond) were investigated in detail and showed decreasing mechanical stiffness with increasing hydrophobic character of linker and effect of its rigidity/flexibility on imine conversion. Besides known linear bis(aminooxy)alkanes with different lengths of the chain, new multifunctional aminooxy-linkers: 1,3,5-tris(aminooxymethyl)benzene and multikis(6-aminooxy-6-deoxy)-ß-cyclodextrin were prepared and shortened the gelation time. The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) analysis showed that despite the aminooxylinkers' cytotoxicity at higher concentrations, the final oxime hydrogels are non-cytotoxic and therefore are suitable for medicinal applications. [ABSTRACT FROM AUTHOR]

Photoresponsive self‐healing polymer gels have great potential in the fields of optical information storage, artificial intelligence, and wearable flexible devices. Herein, a series of photoresponsive self‐healing gels based on dynamic imine bonds are synthesized in which the photoresponsive functions are achieved by the incorporation of the chromophore 1,2‐bis(5′‐formyl‐2′‐methylthien‐3′‐yl)perfluorocyclopentene (DEA) and the fluorophore 2,5‐dimethoxybenzene‐1,4‐diformaldehyde derivatives (DBD) through the Schiff base reactions between DEA/DBD and aminopropylmethylsiloxane‐dimethylsiloxane copolymers. The gels show ultrafast photoresponsive ability with the transition from yellow to blue within 10 s under 254 nm UV–Vis and subsequent color restoration within 20 s under visible light, derived from the fast ring‐closure and ‐opening transition of DEA. Interestingly, the molecular states of DEA have influence on the on–off intensity of the fluorescence. The gels with ring‐opened DEA show stronger blue fluorescence than the ones with ring‐closed DEA. In addition, the cross‐linked dynamic imine bond enables the gels to self‐heal quickly, and the wound disappears within 10 min without any external stimuli. [ABSTRACT FROM AUTHOR]

Stimuli-responsive hydrogels consist of a porous 3D framework that is saturated with solvent. Immersed in a solution bath, these gels can exhibit an enormous volume change due to absorption or release of solution. Depending on the type of gel, this effect can be generated for example by variation of the ion concentration in the surrounding solution bath or by an applied electrical field. The mechanical behavior of these polymers is influenced not only by the solid-state skeleton, but also by the interacting fluid. Thus, a visco-elastic behavior can be observed on the macroscopic scale. Based on the specific properties of the polymer gel and the interaction of the different phases, the determination of the mechanical properties of this material turns out to be non-trivial. In the present work, the mechanical behavior of a poly(acrylamide-co-sodium acrylate) hydrogel in the fully swollen state is investigated by a newly developed tensile test and for longtime investigations by a creep test. For this purpose, two newly developed different experimental setups based on digital image correlation are used. [ABSTRACT FROM AUTHOR]

A new type of hydrogels based on poly(styrene-alt-maleic anhydride) (PSMA) was prepared via Diels-Alder click chemistry. The formulations consisting of tetrazine-functionalized PSMA as a multi-clickable polymer and norbornene-terminated poly(ethylene glycol) (PEG) as a polymeric cross-linker were used as precursors to give ultrafast hydrogels with controlled structures. The hydrogels formed within several minutes under a physiological condition without any catalyst, and their storage modulus (G′) values were in the range 0.3–1.7 kPa suitable for bio-applications. The pore structure and the release profile of doxorubicin hydrochloride (DOX・HCl) of the hydrogels could be manipulated by the molecular weight of PEG. The precursors exhibited practically no depressing effect of the normal HEK293 growth, while the DOX・HCl-loaded hydrogel presented significant anticancer activity towards HeLa cells. The results suggested this biocompatible hydrogel as a potential injectable drug depot for tumor sites.

Polymer gels are a valuable class of polymeric materials that have recently attracted significant interest due to the exceptional properties such as versatility, soft-structure, flexibility and stimuli-responsive, biodegradability, and biocompatibility. Based on their properties, polymer gels can be used in a wide range of applications: food industry, agriculture, biomedical, and biosensors. The utilization of polymer gels in different medical and industrial applications requires a better understanding of the formation process, the factors which affect the gel’s stability, and the structure-rheological properties relationship. The present review aims to give an overview of the polymer gels, the classification of polymer gels’ materials to highlight their important features, and the recent development in biomedical applications. Several perspectives on future advancement of polymer hydrogel are offered.

Ionic conductive hydrogel has recently garnered significant research attention due to its potential applications in the field of wearable and flexible electronics. Nonetheless, the integration of multifunctional and synergistic advantages, including reliable electronic properties, high swelling capacity, exceptional mechanical characteristics, and self-adhesive properties, presents an ongoing challenge. In this study, we have developed an ionic conductive hydrogel through the co-polymerization of 4-Acryloylmorpholine (ACMO) and sodium acrylate using UV curing technology. The hydrogel exhibits excellent mechanical properties, high conductivity, superior swelling capacity, and remarkable self-adhesive attributes. The hydrogel serves as a highly sensitive strain sensor, enabling precise monitoring of both substantial and subtle human motions. Furthermore, the hydrogel demonstrates the capability to adhere to human skin, functioning as a human-machine interface for the detection of physiological signals, including electromyogram (EMG) signals, with low interfacial impedance. This work is anticipated to yield a new class of stretchable and conductive materials with diverse potential applications, ranging from flexible sensors and wearable bio-electronics to contributions in the field of artificial intelligence., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 Published by Elsevier Ltd.)

As advanced radiotherapy techniques progress to deliver a high absorbed dose to the target volume while minimizing the dose to normal tissues using intensity-modulated beams, arcs or stereotactic radiosurgery, new challenges occur to assure that the high treatment dose is delivered homogeneously to the tumor. Small irradiation field sizes (≤1 cm2) that tightly conform to precise target regions and allow for the deliverance of doses with a high therapeutic ratio, are of particular interest. However, the small field dosimetry using conventional dosimeters is limited by the relative large size of the detector. Radiation-sensitive polymer gels have the potential to meet this dosimetry challenge due to their almost unlimited ability in resolving three-dimensional dose distributions of any shape and makes them unique and suitable for the evaluation of dose profiles and the verification of complex doses. In this work, dose distributions in nMAG gels that have been irradiated to different doses by applying a 6 MV FFF photon beam collimated to 1 cm2, were analyzed and the dose profiles were evaluated by applying a gamma passing rate criteria of 3%/3 mm and considering different post-irradiation time intervals between the irradiation and the gels read out process. X-ray CT and NMR imaging procedures were used for the dose evaluation. It was found that the shape and uniformity of the dose profiles were changing due to post-irradiation polymerization and gelation processes, indicating time dependent growing uniformity which was better expressed for the higher delivered doses. It was estimated that in order to obtain acceptably symmetric small field dose profiles, a longer post-irradiation time is needed for getting the full scope of the polymerization as compared with the recently recommended 24 h period between irradiation and the read out processes of the dose gels. An estimated overall uncertainty (double standard deviation, 95% confidence level) of 3.66% was achieved by applying R2 measurements (NMR read out), and a 3.81–applying X-ray CT read out for 12 Gy irradiated gels 56 h post-irradiation. An increasing tendency for the uncertainty was observed with a decreasing post-irradiation time. A gamma passing rate of 90.3% was estimated for the 12 Gy irradiated gels and, 56 h post-irradiation, the X-ray CT evaluated gels as well as a gamma passing rate of 92.7% was obtained for the NMR evaluated gels applying a 3%/3 mm passing criteria.

Stimuli-responsive polymer gels have recently attracted great attention due to their heat/solvent resistance, dimensional stability, and unique sensitivity to external stimuli. In this work, we synthesized thiol-functionalized tetraphenylethylene (TPE) and constructed polymer gels through thiol-ene click reaction. The synthetic process of the polymer gels could be monitored by fluorescence emission of TPE moieties based on aggregation-induced emission mechanism. In addition, due to the dual redoxand acid responsiveness of the polymer gels, in the presence of dithiothreitol and trifluoroacetic acid, fluorescence quenching of the polymer gels can be observed. This stimuli-responsive characteristics endows the polymer gels with potential applications in fluorescent sensing and imaging, cancer diagnosis and selfhealing materials. [ABSTRACT FROM AUTHOR]

Physically crosslinked chitosan hydrogels have better biocompatibility and possess unique functional characteristics but suffer from poor mechanical properties. In the current study, we prepared Cu+-containing physically crosslinked chitosan hydrogels by exploiting ammonia fumigation and reduction of Cu2+ by NaHSO3. The content of Cu+ in the prepared hydrogels was in a low range of 4.88–29.27 μmol/g. The mechanical strength of the CTS-Cu+/NH3 hydrogels was remarkably improved up to 0.25 MPa and the elongation at break increased with rising content of Cu+ due to the dynamic crosslinks between chitosan and Cu+. Moreover, the CTS-Cu+/NH3 hydrogels demonstrated evident shape memory after exposure to air by exploiting the different coordination number of Cu2+ and Cu+. Thus, the prepared hydrogels may have good potential applications as biomedical materials.