Interpenetrating Polymer Networks Research Articles

Smart Hydrogel Reactor of Poly(N-isopropylacrylamide)/Polyethylene Glycol Interpenetrating Polymer Networks for Oxidative Coupling of 2-Naphthol

AbstractHydrogels with an interpenetrating polymer network (IPN) structure composed of poly(N-isopropylacrylamide) (poly-NIPAM) gel and a gel containing polyethylene glycol (PEG) chains were synthesized. They showed a typical temperature-responsive volume change in water owing to the constructed poly-NIPAM gel component. Oxidative coupling of 2-naphthol with IPN cryogels and a conventional catalyst, the CuCl2 complex of N,N,N′,N′-tetramethylenediamine, was conducted in water under an O2 atmosphere; the IPN gel prepared from PEG with a larger molecular weight of 11000 afforded a product with a good yield of 73% (91% conv.) during the reaction in basic media. The hydrogel effectively promoted the reaction but hardly produced any product without the catalyst, acting as a reactor vessel in the water. Owing to the low durability of the PEG gel component for hydrolysis, a limitation was also suggested during experiments on the recyclability of the hydrogel.

The role of post‐cure cycle on the thermomechanical properties of soy‐based polyurethane thermosets

AbstractA systematic study of the post‐cure cycle of soy‐based polyurethane thermosets was conducted as a function of crosslinker content, post‐cure temperature and time. An improvement of 207% of the flexural strength, up to 175 MPa, was measured by increasing the crosslinking content to 60 wt% and by using a post‐cure cycle temperature of 110°C. Similarly, the flexural modulus also increased by 199%, up to 3.2 GPa, while maintaining a flexural strain to failure of 6.60%. In situ studies of the post‐cure cycle using dynamical mechanical analysis revealed the interplay between the two interpenetrating polymer networks as a function of crosslinker content. At a crosslinker content below 40 wt%, two rubbery to glass transition temperatures (Tg) were found at 60 and 200°C, respectively. At 60 wt%, only one Tg at temperatures close to the degradation temperature was identified (250°C). Scanning electron microscope micrographs of the fracture surface revealed the formation of stress induced cracks which were mitigated through the use of a temperature stepped post‐cure cycle. The formation of soft segments with high degradation temperatures (485°C) were revealed by thermogravimetric analysis, which can be attributed to the presence of additional covalent bonds such as allophanate and carbodiimide that were also identified through Fourier transform infrared analysis. The results revealed in this work are key for the development of biobased polyurethanes applied for the polymer composite industry. In this regard, this study represented the first analysis of the post‐cure cycle of a soy‐based polyurethane thermoset.

Hybrid Fabrication of Prestrain-Locked Acrylic Dielectric Elastomer Thin Films and Multilayer Stacks.

Dielectric elastomers based on commercial acrylic dielectric elastomers (VHB adhesive films) are widely investigated for soft actuators due to their large electrically driven actuation strain and high work density. However, the VHB films require prestretching to overcome electromechanical instability, which adds fabrication complexity. In addition, their high viscoelasticity leads to a low response speed. Interpenetrated polymer networks (IPNs) are developed to lock the prestrain in VHB films, resulting in free-standing films that are capable of large-strain actuation. In this work, a prestrain-locked high-performance dielectric elastomer thin film (VHB-IPN-P) by introducing 1,6-hexanediol diacrylate to create an IPN in the VHB network and a plasticizer to enhance the actuation speed is reported. VHB-IPN-P based actuators exhibit stable actuation at 60% strain up to 10Hz and reach a peak energy density of 102 Jkg⁻1 . In addition, a hybrid process is also developed for the fabrication of multilayer stacks of VHB-IPN-P with strong inter-layer bonding and structural integrity. Four-layer stacks fabricated preserve the strain and energy density of single-layer VHB-IPN-P films but with linearly scaled force and work output.

Fabrication and testing of bioinspired microstructured alumina composites with sacrificial interpenetrating polymer bonds

Bioinspired composites exhibit well-defined microstructures, where anisotropic ceramic particles are assembled and bonded by an organic matrix. However, it is difficult to fabricate these composites where both the ceramic particles and organic matrix work together to unlock toughening mechanisms, such as shear dissipation, particle rotation and interlocking, etc, that lead to stiff, strong, and tough mechanical properties. Here, we produce composites inspired by seashells, made of alumina microplatelets assembled in complex microstructures and that are physically bonded by a small amount of interpenetrated polymer network (IPN) made of polyacrylamide (PAM) and poly-N-isopropylacrylamide (PNIPAM). The fabrication employs magnetically assisted slip-casting to orient the microplatelets as desired, and in situ gelation of the IPN, followed by drying. The process was successful after carefully tuning the slip casting and gelation kinetics. Samples with horizontal, vertical, and alternating vertical and horizontal microplatelets orientations were then tested under compression. It was found that the IPN threads bonding the microplatelets acted as sacrificial bonds dissipating energy during the compression. Paired with the alternating microstructure, the IPN significantly enhanced the compressive toughness of the composites by 205% as compared to the composites with horizontal or vertical orientation only, with less than 35% reduction on the stiffness. This study demonstrates that microstructure control and design combined with a flexible and tough matrix can effectively enhance the properties of bioinspired ceramic polymer composites.

Bilayer Actuator Film for Urea Biosensing with Dual Responsiveness: Bending Actuation and Photonic Color Change.

A noninvasive sweat-based biosensor was developed for urea detection using a photonic bilayer actuator film (BAF) consisting of an interpenetrating polymer network (IPN) as the active layer and a flexible poly(ethylene terephthalate) (PET) substrate as the passive layer (IPN/PET). The active IPN layer comprises intertwined solid-state cholesteric liquid crystal and poly(acrylic acid) (PAA) networks. Urease was immobilized in the PAA network in the IPN layer of the photonic BAF. The interaction with aqueous urea altered the curvature and photonic color of the photonic urease-immobilized IPN/PET (IPNurease/PET) BAF. The curvature (and wavelength of the photonic color) of the IPNurease/PET BAF increased linearly with urea concentration (Curea) in the range of Curea = 20-65 (and 30-65) mM with a limit of detection value of 1.42 (and 1.34) mM. The developed photonic IPNurease/PET BAF exhibited high selectivity toward urea and excellent spike test results with real human sweat. This novel IPNurease/PET BAF is promising because it enables battery-free, cost-effective, and visual detection-based analysis without the use of sophisticated instruments. Furthermore, the application of this photonic IPN/PET BAF can be easily extended to other biosensors by immobilizing other receptors on the IPN.

An interpenetrating polymer networks structure formed by in situ crosslinking of flame retardant for improvement in mechanical properties and flame retardancy of epoxy resins

AbstractEpoxy resins (EPs) possess flammable characteristics inherently, and various methods have been utilized to enhance their flame retardancy. However, the improvement of flame retardancy may reduce its mechanical properties at the same time. Hence, this work synthesized a novel interpenetrating polymer network structure by introducing double bonds into flame retardants based on crosslinking strategy. When the flame retardant was crosslinked inside the EPs, the increased crosslink density improved the mechanical properties and the fire retardancy of the EP thermosets. With the addition of just 3 wt% of a crosslinked flame retardant, its vertical combustion achieved grade V‐0 and had a limited oxygen index of 31.8%. In the cone calorimeter test, the heat release rate was significantly decreased by 56.7% compared with pure EP when the crosslinked flame retardant reached 5 wt%. The study on the pyrolysis behavior of the material and the residual char further revealed that the flame retardant has a biphasic flame‐retardant effect.

A robust and fluorescent nanocomposite hydrogel with an interpenetrating polymer network based on graphene quantum dots

AbstractHerein, a robust and fluorescent nanocomposite hydrogel polyvinyl alcohol/poly(N‐methylol acrylamide)/graphene quantum dots (PVA/PNMA/GQDs) with interpenetrating polymer network was made‐up by in‐situ radical polymerization and freeze–thaw method simultaneously. Because of GQDs trapped within the gel matrix as a result of the potent hydrogen bonds generated among PVA, PNMA, and GQDs, the nanocomposite hydrogel with an interpenetrating polymer network displayed strong fluorescence and enhanced mechanical properties. The obtained nanocomposite hydrogel could emit stable bright blue fluorescence at 365 nm radiation. Moreover, the obtained nanocomposite hydrogels were selective to Fe3+ ions and demonstrated a rapid and consistent response to Fe3+ ions ranging from 20 to 120 μmol/L. Meanwhile, the PVA/PNMA/GQDs hydrogel showed excellent mechanical properties. The compressive strength and strain of the nanocomposite hydrogel were 20.39 MPa and 94.53%, respectively. The tensile fracture strength was 303.06 kPa and the corresponding fracture strain was 198%. Additionally, the gel also possessed extreme fatigue resistance and could tolerate repeated compression without cracking. Therefore, these robust and fluorescent nanocomposite hydrogels have potential applications in flexible sensors for certain metal ions detection and information storage.

High-Speed and High-Resolution 3D Printing of Self-Healing and Ion-Conductive Hydrogels via μCLIP

Conductive and self-healing (SH) hydrogels have been receiving continuous attention, which could broaden the design of ionotronic devices for health monitoring systems and soft robots with the ability to repair damage autonomously. So far, three-dimensional (3D) fabrication of such SH hydrogels is mainly limited to traditional molding/casting or extrusion-based 3D printing methods, which limits the formation of sophisticated structures with high-resolution features. Furthermore, the need of external stimuli (e.g., water, heat, and pH change) to achieve SH behavior could restrict their wide application. Herein, we report an ion-conductive SH hydrogel suitable for a home-built high-resolution and high-speed 3D printing process, micro continuous liquid interface production (μCLIP). This material system relies on interpenetrating polymer networks (IPN) hydrogel formed by physically cross-linked poly(vinyl alcohol) combined with chemically/ionically cross-linked poly(acrylic acid) and ferric chloride. By carefully optimizing the resin’s composition, we can balance high-resolution printability and superb SH capability, at the same time manifesting sufficient ion conductivity. Specifically, complex 3D structures with microscale features (down to 100 μm) can be printed at speeds up to 16.5 μm s–1. Upon damage occurs, hydrogen bonds within hydroxyl and carboxyl groups, as well as ionic bonds generated from ferric ions, contribute together to achieve fast and high efficiency SH, which can restore 90% (100%) of the original mechanical strength at room temperature within 4 h (8 h) without any external stimulus. In addition, both the as-printed and self-healed hydrogels manifest superior ion conductivity and stretchability. Therefore, the SH hydrogels can be rapidly printed and tailored as customized wearable sensors, and the sensing capabilities were quantitatively investigated and compared. In terms of applications, SH hydrogel-based knuckle sensors were prototyped to detect a finger’s folding and unfolding motions.

Role of Nanoscale Heterogeneity in the Mechanical Performance of Hybrid Elastomers

Silicone–organic interpenetrating polymer networks (IPNs) are hybrid materials with enhanced mechanical properties relative to pure silicones. Here, we compare structure–property relationships of graft-IPNs of polydimethylsiloxane (PDMS) made with methyl methacrylate (MMA) and isobornyl methacrylate (IBoMA). We found evidence for increased polymer–polymer mixing in the PDMS/PIBoMA graft-IPNs, which was impacted by the higher relative compatibility of these two polymers compared to PDMS/PMMA. These PDMS/PIBoMA hybrid materials possessed fracture toughness values up to 400× greater than unreinforced PDMS elastomers, contrasted by the lower toughness values and highly phase separated morphologies of the PDMS/PMMA hybrids. Increased temperature reduced the fracture and fatigue resistance of the hybrids as nanoscale mechanical heterogeneity was lost between PDMS and the methacrylate polymers, which is consistent with the behavior of existent silicone resin-filled silicone materials.

Construction of starch-sodium alginate interpenetrating polymer network and its effects on structure, cooking quality and in vitro starch digestibility of extruded whole buckwheat noodles

The effects of different concentrations and crosslinking methods of sodium alginate (SA) on the structure, cooking quality and in vitro starch digestibility of extruded whole buckwheat noodles were investigated. The results showed that SA could interact with starch through hydrogen bonding, resulting in decrease of the relative crystallinity of starch and improvement of thermal stability. Addition of 1% SA significantly decreased the cooking loss from 15.33% to 8.64%, predicted glycemic index (pGI) from 84.76 to 78.92, and increased the noodle hardness from 2260.16 g to 2809.34 g，as well as the content of resistant starch (RS) from 37.25 to 45.47. Two different crosslinking methods, dynamic blending crosslinking (DBC) and in-situ polymerization crosslinking (ISPC) of SA at 1% induced by CaCl2 were attempted to further improve the properties of extruded buckwheat noodle. SEM showed that both starch gel network and SA gel network existed. DBC induced fast gelation of SA molecules, and the aggregated SA gels disrupted the continuity of the starch gel network. As a comparison, SA network was evenly distributed in starch network when ISPC was applied, indicating Starch-SA interpenetrating polymer network (IPN) was successfully constructed. The resultant cooking loss, surface adhesion and pGI value significantly decreased to 6.58%, −19.59 g s, 69.25, while the noodle hardness and content of RS increased to 6220.90 g, 61.03%, respectively. In a word, the formation of Starch-SA IPN enhanced cooking quality and reduced starch digestibility of extruded whole buckwheat noodles.

The effect of GelMA/alginate interpenetrating polymeric network hydrogel on the performance of porous zirconia matrix for bone regeneration applications

Bone tissue is a natural composite, exhibiting complicated structures and unique mechanical/biological properties. With an attempt of mimicking the bone tissue, a novel inorganic-organic composite scaffolds (ZrO2-GM/SA) was designed and prepared via the vacuum infiltration method and the single/double cross-linking strategy by blending GelMA/alginate (GelMA/SA) interpenetrating polymeric network (IPN) into the porous zirconia (ZrO2) scaffold. The structure, morphology, compressive strength, surface/interface properties, and biocompatibility of the ZrO2-GM/SA composite scaffolds were characterized to evaluate the performance of the composite scaffolds. Results showed that compared to ZrO2 bare scaffolds with well-defined open pores, the composite scaffolds prepared by double cross-linking of GelMA hydrogel and sodium alginate (SA) presented a continuous, tunable and honeycomb-like microstructure. Meanwhile, GelMA/SA showed favorable and controllable water-uptake capacity, swelling property and degradability. After the introduction of IPN components, the mechanical strength of composite scaffolds was further improved. The compressive modulus of composite scaffolds was significantly higher than the bare ZrO2 scaffolds. In addition, ZrO2-GM/SA composite scaffolds had highly biocompatibility and displayed a potent proliferation and osteogenesis of MC3T3-E1 pre-osteoblasts compared to bare ZrO2 scaffolds and ZrO2-GelMA composite scaffolds. At the same time, ZrO2-10GM/1SA composite scaffold regenerated significantly greater bone than other groups in vivo. This study demonstrated that the proposed ZrO2-GM/SA composite scaffolds had great research and application potential in bone tissue engineering.

The preparation of double network hydrogel with high mechanical properties by photopolymerization under the green LED irradiation and enhancement of wet adhesion by tannic acid

Double network hydrogel with excellent mechanical properties is a polymer material composed of interpenetrating polymer network structure. In this study, poly(acrylamide-co-acrylic acid)/sodium alginate (P(AAM-co-AAC)/SA) hydrogels were rapidly prepared by photopolymerization under green LED irradiation. Subsequently, poly(acrylamide-co-acrylic acid)/sodium alginate/tannic acid (P(AAM-co-AAC)/SA/TA) hydrogels were prepared by immersion method. The morphology, mechanical properties, the wet adhension ability and swelling behaviour morphology of P(AAM-co-AAC)/SA/TA hydrogels were studied in detail. The double network hydrogel has excellent mechanical properties, with the elongation at break and tensile strength reaching 862% and 0.77 MPa respectively. The hydrogel with tannic acid showed excellent adhesion, wet adhesion and anti-swelling capability. Our research provides a more efficient and environmentally friendly preparation method for hydrogels used in wet environment.

Salt-resistant agarose-polyvinylpyrrolidone composite hydrogel with pitted-surface towards highly efficient water desalination and purification

In recent years, solar energy interfacial evaporation technology has been extensively explored for seawater desalination and wastewater treatment. However, salt accumulation and complex fabrication of evaporator largely constrains the applications of this technology in practice. Here, one type of interpenetrating polymer network hydrogel composing of agarose (AG) and polyvinylpyrrolidone (PVP) using polypyrrole (PPy) as the light absorbent was fabricated via “hot-ice” template method, which was featured with pitted-surface and microchannels structure. The evenly arranged pits on the surface of the hydrogel can absorb the sunlight as much as possible and convert it into heat energy, improving the efficiency of photothermal absorption. The water channels generated by the formation of CaCl2·6H2O crystals can transport water from the bottom to the evaporation interface elevating the transmission rate and accelerating the exchange of gradient salt concentration. As consequences, excellent salt resistance of the hydrogel can be obtained, achieving seawater evaporation rate as high as 3.2 kg m−2 h−1. In addition, the outstanding ion rejection performance, strong acid/alkali purification capability, and good treatment capacity for heavy metal ions and dye wastewater were also demonstrated.

Chitosan interpenetrating polymer network hydrogels for oil–water and emulsion separation

AbstractHydrogels have obtained extensive attention in oil–water separation due to their high hydrophilicity and weak viscosity. However, most hydrogels have limited applications due to their subpar mechanical qualities. The interpenetrating network gives the hydrogel material high mechanical properties due to the presence of physical and chemical crosslinking. Hence, polyvinyl alcohol/chitosan/polyacrylamide interpenetrating polymer network hydrogel (HAPC‐Gel) was created in this study. HAPC‐Gel coating filter cloth showed underwater super‐oleophobic (the oil contact angles about 159°) and could stably separate oil–water mixtures in different oil phases and complex environments (acids, bases, salts), and the removal rate is still above 99% after 20 cycles of separation. Furthermore, the water could be divided from the oil‐in‐water emulsion. These results indicate that HAPC‐Gel composites have promising applications in oil–water separation.

Hierarchically porous hydrogel electrolyte prepared from interpenetrating polymer networks for flexible Zn-Air batteries

Gel polymer electrolyte (GPE) based flexible zinc-air batteries (ZABs) are considered promising power sources for next-generation wearable devices because of their high specific energy density, low cost, high safety, and environmental friendliness. However, the liquid component in GPE is susceptible to evaporation through the air cathode, drastically reducing the cell performance and lifetime. Poly(vinyl alcohol) (PVA) is the most widely adopted ion conductive polymer, but its poor water retention and low ionic conductivity hinder the widespread commercialization of flexible ZABs. A hierarchically porous (HP) PVA and poly(acrylic acid) (PAA) hybrid GPE is developed to address the aforementioned issues. The polymerization of acrylic acid in a PVA matrix forms a semi-interpenetrating polymer network involving a unique HP structure inside the membrane. The PAA-rich lotus-seed-like pores fundamentally improve electrolyte uptake and retention properties, and enhance ionic conductivity. The HP-PVA/PAA hybrid GPE delivers excellent cycling stability, rate characteristics, and power output in ZABs. Furthermore, HP-PVA/PAA based flexible ZABs incorporated into the customized strap demonstrates their feasibility for powering the wearable smart watch.

Simultaneous enhancement in interlaminar– shear strength and fracture toughness through nano Al2O3 dispersion in glass fiber/IPN multiscale composites

Simultaneous implementation of two polymer hybridisation routes, namely, interpenetrating polymer network (IPN) formation and nanofiller (nano Al2O3) addition, resulted in considerable increments in the mechanical performance of GFRP composites. Improvements of ∼18%, ∼8%, ∼14%, ∼19 %, and ∼29% in flexural strength, tensile strength, interlaminar shear strength (ILSS), critical strain energy release rate (GIC) during mode-I interlaminar fracture toughness (ILFT), and GIIC during mode-II ILFT values of nano-Al2O3 modified composites, respectively, were observed over composite without nano Al2O3. Composite with 0.1 wt.% of nano Al2O3 showed the highest mechanical properties in all the modes of testing except for mode-II ILFT testing, where composite with 0.4 wt.% of nano Al2O3 showed the highest toughness value. The synergy between the constituents and the thermal stability of the composites were analyzed via Fourier transform infrared spectroscopy and differential scanning calorimetry, respectively. Fractography was performed to understand the composites' failure criteria and toughening mechanisms.

4D Printing of Triple-Shape Memory Cyanate Composites Based on Interpenetrating Polymer Network Structures.

The triple-shape memory polymer (TSMP) can be programmed into two temporary shapes (S1 and S2) and shows an ordinal recovery from S2 to S1 and eventually to the permanent shape upon heating, which realizes more complex stimulus-response motions. We introduced a novel strategy for forming triple-shape memory cyanate ester (TSMCE) resins with high strength and fracture toughness via three-step curing, including four-dimensional (4D) printing, UV post-curing, and thermal curing. The obtained TSMCE resins presented two separated glass transition temperature (Tg) regions due to the formation of an interpenetrating polymer network (IPN), which successfully endowed the polymers with the triple-shape memory effect. The two Tg increased with the increasing cyanate ester (CE) prepolymer content; their ranges were 82.7-102.1 °C and 164.4-229.0 °C, respectively. The fracture strain of the IPN CE resin was up to 10.9%. Moreover, the cooperation of short carbon fibers (CFs) and glass fibers (GFs) with the polymer-accelerated phase separation resulted in two well-separated Tg peaks exhibiting better excellent triple-shape memory behaviors and fracture toughness. The strategy for combining the IPN structure and 4D printing provides insight into the preparation of shape memory polymers integrating high strength and toughness, multiple-shape memory effect, and multifunctionality.

Carbonic Anhydrase Enhanced UV-Crosslinked PEG-DA/PEO Extruded Hydrogel Flexible Filaments and Durable Grids for CO2 Capture.

In this study, poly (ethylene glycol) diacrylate/poly (ethylene oxide) (PEG-DA/PEO) interpenetrating polymer network hydrogels (IPNH) were extruded into 1D filaments and 2D grids. The suitability of this system for enzyme immobilization and CO2 capture application was validated. IPNH chemical composition was verified spectroscopically using FTIR. The extruded filament had an average tensile strength of 6.5 MPa and elongation at break of 80%. IPNH filament can be twisted and bent and therefore is suitable for further processing using conventional textile fabrication methods. Initial activity recovery of the entrapped carbonic anhydrase (CA) calculated from esterase activity, showed a decrease with an increase in enzyme dose, while activity retention of high enzyme dose samples was over 87% after 150 days of repeated washing and testing. IPNH 2D grids that were assembled into spiral roll structured packings exhibited increased CO2 capture efficiency with increasing enzyme dose. Long-term CO2 capture performance of the CA immobilized IPNH structured packing was tested in a continuous solvent recirculation experiment for 1032 h, where 52% of the initial CO2 capture performance and 34% of the enzyme contribution were retained. These results demonstrate the feasibility of using rapid UV-crosslinking to form enzyme-immobilized hydrogels by a geometrically-controllable extrusion process that uses analogous linear polymers for both viscosity enhancement and chain entanglement purposes, and achieves high activity retention and performance stability of the immobilized CA. Potential uses for this system extend to 3D printing inks and enzyme immobilization matrices for such diverse applications as biocatalytic reactors and biosensor fabrication.

The first results of obtaining a hybrid hydrogel based on fibrin and polyvinyl alcohol: comparison with monocomponent hydrogels

Fibrin displays promising characteristics for tissue engineering. However, it has suboptimal physical and mechanical properties when used as a material for cardiovascular applications. Obtaining an interpenetrating polymer network (IPN) hydrogel based on fibrin and polyvinyl alcohol (PVA) can improve the physical and mechanical characteristics and shrink behavior of fibrin.Aim: To perform sequential polymerization of fibrin and PVA to obtain IPN hydrogel and analyze its properties in comparison with monocomponent hydrogels.Material and Methods. Fibrinogen was isolated from the peripheral blood of patients using ethanol precipitation, then polyvinyl alcohol dissolved in saline was added to it. First, fibrin polymerization was initiated by adding calcium chloride to the solution. Then, it was followed by polyvinyl alcohol undergoing freeze–thaw cycles. Thus, a hydrogel based on fibrin and PVA, samples from pure fibrin and pure polyvinyl alcohol were prepared. We studied the structure of hydrogels, their physical and mechanical properties, shrink behavior and biological activity. Statistical data processing was carried out using the GraphPad Prism 6 software.Results. 3D structure of the hydrogel is presented by polyvinyl alcohol polygonal cavities with a network of thin fibrin fibers. The distribution of components was equal in the inside of the samples, while polyvinyl alcohol prevails on the surface. Elongation (247 (220.0; 293.2)%; p = 0.0005) and Young’s modulus (0.09 (0.11; 0.13) mPa; p = 0.0001) of the hydrogel were statistically significantly higher compared to fibrin values. The hydrogel did not shrink, unlike fibrin that shrunk (11-fold decrease in volume). The number of adherent endothelial cells on the hydrogel matrices was 8 times higher than on polyvinyl alcohol, but 10 times lower than on fibrin. There was no proliferative activity of cells on polyvinyl alcohol, but 13.6% of proliferating cells were noted on the IPN hydrogel, and 59.52% on fibrinConclusion. Using sequential polymerization to obtain the IPN hydrogel based on fibrin and polyvinyl alcohol provides an equal distribution of fibers in the thickness of the material, making it possible to obtain hydrogels with improved mechanical properties and shrink behavior. However, the components on the surface of the IPN hydrogel need to be redistributed - more polyvinyl alcohol should be added still maintaining a relatively low adhesiveness of the material. Therefore further research is necessary to create the most optimal conditions for cell activity.

Fabrication of Hydrogel-Based Composite Fibers and Computer Simulation of the Filler Dynamics in the Composite Flow.

Fibrous structures with anisotropic fillers as composites have found increasing interest in the field of biofabrication since they can mimic the extracellular matrix of anisotropic tissues such as skeletal muscle or nerve tissue. In the present work, the inclusion of anisotropic fillers in hydrogel-based filaments with an interpenetrating polymeric network (IPN) was evaluated and the dynamics of such fillers in the composite flow were analyzed using computational simulations. In the experimental part, microfabricated rods (200 and 400 μm length, 50 μm width) were used as anisotropic fillers in extrusion of composite filaments using two techniques of wet spinning and 3D printing. Hydrogels such as oxidized alginate (ADA) and methacrylated gelatin (GelMA) were used as matrices. In the computational simulation, a combination of computational fluid dynamics and coarse-grained molecular dynamics was used to study the dynamics of rod-like fillers in the flow field of a syringe. It showed that, during the extrusion process, microrods are far from being well aligned. Instead, many of them tumble on their way through the needle leading to a random orientation in the fiber which was confirmed experimentally.