Polymer Gel Network Research Articles

Environmental-Friendly, Long-Lastingly Moist Phase Change Gel with Tunable Cross-Linking Time for Effective Borehole Sealing.

Flexible environmental phase change gel (EPCG) is a promising and attractive material for borehole sealing due to its relatively lower usage, tunable cross-linking time, and potential degradable properties. However, conventional borehole sealing materials lack a lower manufacturing cost, lower reaction temperature, remarkable antimold function, and admirable hole sealing performance for long-term high-performance borehole sealing. Hence, it remains a critical challenge to realize a flexible phase-change gel featuring tunable cross-linking time, antimold ability and degradability, and long-lasting moist performance for high-performance borehole sealing. Herein, we illustrate a facile approach to fabricate the borehole sealing materials based on environmentally friendly, antimold, long-lasting moist composite phase-change gel fabricated from a modified cellulose gel polymer network. The prepared phase change gel presents adjustable cross-linking time with the initial setting time of 30-60 min, which could be used to seal holes with different drilling parameters. Furthermore, the fabricated gel illustrates reliable water retentiveness performance and antimold ability, assuring the long-period borehole sealing effect. Furthermore, EPCG has been applied for borehole sealing and shows great sealing ability and gas extraction performance. Therefore, this work paves the way to fabricate a flexible phase-change gel featuring tunable cross-linking time, antimold ability, and long-lasting moist performance for high performance borehole sealing.

Photopatterned Hybrid Supramolecular/Polymer Hydrogels for Controlled Heparin Release and Stem Cell Growth

AbstractThis paper reports hybrid gels combining a low‐molecular‐weight gelator (LMWG) and a photoinitiated crosslinked polymer gel (PG). The presence of the PG enhanced the stiffness and strength of the gel. The gels were loaded with heparin, and in the hybrid gel, the interpenetrated LMWG and PG networks somewhat restricted its release. In terms of stem cell growth, the hybrid gel significantly improved the performance of the PG because of the presence of the LMWG, which is an excellent substrate for stem cells in its own right. Furthermore, the presence of heparin in the hybrid gels also enhanced stem cell proliferation over longer timescales. Finally, these gels were photopatterned within the well‐plates used for tissue culture, with patterning helping control stem cell proliferation. In summary, these hybrid gels combine the advantageous features of both LMWG and PG: rheological performance is endowed by the PG with stem cell compatibility provided by the LMWG. The hybrid gels also control the release of the bioactive agent heparin and have capacity to be shaped and patterned. Patterned gels such as these, capable of directing stem cell growth, have potential in regenerative medicine.

Imaging a solvent‐swollen polymer gel network by open liquid transmission electron microscopy

AbstractVisualizing 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.

Fabrication of high‐performance acrylate grouting materials from tailor made magnesium acrylate solutions

AbstractAcrylate grouting (AG) material is a low‐viscosity aqueous solution capable of forming an elastic water‐plugging gel after being injected into seepage cracks. This study highlights the fabrication and performance of AG materials, specifically emphasizing the use of magnesium acrylate (MgDA) as the principal precursor for the polymer gel network. Additionally, 2‐(dimethylamino)ethyl methacrylate (DMAEMA) serves as a bifunction crosslinker and accelerator, while sodium persulfate and potassium ferricyanide act as initiator and retarder, respectively. AG materials are made of these four key ingredients mixed in an aqueous solution, and then polymerized into a highly elastic water‐plugging gel. Our systematic investigation indicated that the MgDA and DMAEMA concentrations significantly influence the performance of the AG material. The optimized AG material formulation containing 24% MgDA and 1.4% DMAEMA, exhibited an elongation at break of 1040%, a water absorption of 67% and a compressive strength of 363 kPa in grouted sand. The gel time could be adjusted from under 20 s to more than 20 min, offering versatility to meet various application requirements. Beyond its good bonding performance and superior extrusion resistance, the AG materials displayed excellent water‐plugging effect. Impressively, even after extending the closed water test to 360 days, the gel displayed no significant change in color or signs of degradation, and the treated crack remained in a deep dry state with no evidence of leakage, confirming the AG material's superior durability. With its advantageous permeability and excellent water‐plugging effect, the AG material is well‐suited for applications in micro‐crack sealing, seepage prevention and stratum reinforcement grouting.

Effects of sinapine on structure, rheology, stability, and antioxidant properties of protein-based capillary bridging oleogels

The development of oleogels has received increasing attention due to their health benefits and potential to replace saturated or trans fats. This work reports a preparation of sinapine-protein oleogels using a capillary suspension method, comparing the effect of different concentrations of sinapine and the three proteins on the stability of the system. The results show that the incorporation of 4–8 μg/mL of sinapine promoted the formation of capillary bridges between protein particles. The oil constraint capacity of WPI-oleogels is improved by about 20 % due to the addition of sinapine. The structural integrity of the oleogels was highly dependent on the protein hydrophilic capacity and the concentration of secondary fluid-sinapine. In addition, the stabilized oleogels prepared by sinapine had high energy storage modulus and thixotropic recovery, indicating the stabilizing effect of sinapine. Thus, the interfacially adsorbed particles and the polymer gel network jointly contribute to the dense structure of the oleogels. That the preparation of sinapine-protein oleogels based on capillary suspension has potential applications in foods with adjustable rheological and textural properties.

Investigation into the gel substrate fabrication of a novel ammonium amine explosive and its generic properties exploration

Gels from crosslinked polymer chains are promising soft matters which are attracting enormous research interests in applications such as biomedical, sensing, antibiofouling, intelligence and advanced manufacturing. In this work, gels composed of polymer network are used for components stabilization in a novel water-resistant explosive, termed as ammonium amine explosive. The ammonium amine explosive is endowed with water resistance taking advantages of the swelling property of polymer network. Moreover, this ammonium amine explosive is featured by its facile, mild, intrinsically safe and energy saving fabrication method compared to universal explosives’ manufacturing technique which generally includes high temperature or high-speed shearing process. The density and microstructure of the explosive gel substrates is found to be pH dependent. This phenomenon is chemically explained by the crosslinking and foaming reactions of the explosive gel substrates, and further confirmed by water resistance experiments performed on the ammonium amine explosive and the mechanical tests performed on the gel substrates. This work presents a unique application of polymer gel network in a novel engineering explosive, gives a chemical viewpoint into the explosive characterization, and provides a prospective perspective to investigate the other performances and structure of this water-resistant explosives in the future.

Laponite-Supported Gel Polymer Electrolyte with Multiple Lithium-Ion Transport Channels for Stable Lithium Metal Batteries.

Lithium metal batteries have emerged as a promising candidate for next-generation power systems. However, the high reactivity of lithium metal with liquid electrolytes has resulted in decreased battery safety and stability, which poses a significant challenge. Herein, we present a modified laponite-supported gel polymer electrolyte (LAP@PDOL GPE) that was fabricated using in situ polymerization initiated by a redox-initiating system at ambient temperature. The LAP@PDOL GPE effectively facilitates the dissociation of lithium salts via electrostatic interaction and simultaneously constructs multiple lithium-ion transport channels within the gel polymer network. This hierarchical GPE demonstrates a remarkable ionic conductivity of 5.16 × 10-4 S cm-1 at 30 °C. Furthermore, the robust laponite component of the LAP@PDOL GPE forms a barrier against Li dendrite growth while also participating in the establishment of a stable electrode/electrolyte interface with Si-rich components. The in situ polymerization process further improves the interfacial contact, enabling the LiFePO4/LAP@PDOL GPE/Li cell to exhibit an impressive capacity of 137 mAh g-1 at 1C, with a capacity retention of 98.5% even after 400 cycles. In summary, the developed LAP@PDOL GPE shows great potential in addressing the critical issues of safety and stability associated with lithium metal batteries while also delivering improved electrochemical performance.

Frictional properties of phase-separated agarose hydrogels in water permeation.

We studied the friction coefficient between the polymer gel network and water f for thermoreversible agarose gels under various conditions of agarose concentration and gelation temperature. Since agarose gels exhibit phase separation below the gelation temperature, f strongly depends on the thermal history. We found that the friction coefficient of the phase-separated agarose gel normalized by the water viscosity, f/η, is expressed as f/η = S/ξνSD where ξSD is the frictional pore size and ν and S are constant parameters. ξSD corresponds to the correlation length of the frozen density fluctuations of the polymers via spinodal decomposition determined from small-angle light scattering. The least-squares analysis of the results shows that the exponent is ν ≃ 2 with the numerical constant of S ≃ 105/2π. The results suggest that the frictional properties of phase-separated agarose gels are dominated by the dilute regions of the bicontinuous gel structure.

Supramolecular polymer network gels constructed by a pillararene-containing polymer and their applications in adhesion between semihard materials

Two types of supramolecular gels based on one kind of pillararene-containing polymer with multiple-stimuli-responsiveness were fabricated and showed strong adhesive strength in the semihard state.

A coordination driven 'heat-set' Zr-gel: efficient fluorophore probe for selective detection of Fe3+ and nitrofuran-based antibiotics and smart approach for UV protection.

Nature creates definite architecture with fluorescence capabilities and superior visual adaptation in many organisms, e.g., cephalopods, which differentiates them from their surroundings in the context of colour and texture that allows them to use this in defence, communication, and reproduction. Inspired by nature, we have designed a coordination polymer gel (CPG)-based luminescent soft material where the photophysical properties of the material can be tuned using a low molecular weight gelator (LMWG) with chromophoric functionalities. Herein, a water-stable coordination polymer gel-based luminescent sensor was created using zirconium oxychloride octahydrate as a metal source and H3TATAB (4,4',4''-((1,3,5-triazine-2,4,6-triyl)tris(azanediyl))tribenzoic acid) as a LMWG. The tripodal carboxylic acid gelator H3TATAB with a triazine backbone induces rigidity in the coordination polymer gel network structure along with the unique photoluminescent properties. The xerogel material can selectively detect Fe3+ and nitrofuran-based antibiotics (i.e., NFT) in aqueous medium through luminescent 'turn-off' phenomena. This material is a potent sensor because of the ultrafast detection of the targeted analytes (Fe3+ and NFT), with consistent efficacy in quenching activity up to five consecutive cycles. More interestingly, colorimetric, portable handy paper strip, thin film-based smart detection approaches (under an ultraviolet (UV) source) were introduced to make this material a viable sensor probe in real-time applications. In addition, we developed a facile method to synthesize CPG-polymer composite material that can be utilized as a transparent thin film to protect against UV radiation (200-360 nm), with approximately 99% absorption efficacy.

Rational design cold-set interpenetrating network hydrogel based on wheat bran arabinoxylans and pea protein isolates for regulating the release of riboflavin in simulated digestion

Cold-set interpenetrating polymer network gels as riboflavin (RF) delivery vehicles based on wheat bran arabinoxylans (AX) and pea protein isolate (PPI) were developed via enzymatic-crosslinking. The impact of AX concentrations on the physicochemical property, in vitro digestion property and microstructure of IPN gels was explored. Increased concentrations of AX enhanced the viscoelasticity of IPN gels and resulted in a more compact microstructure. However, at a concentration of 5.0 % (w/v), the faster and stronger crosslinking of AX molecules caused separate network gel between PPI and AX. The IPN gel improved the encapsulation efficiency and release property of embedded RF as compared to PPI gel. SEM results showed that IPN gel maintained a complete network structure after gastric digestion. Particularly, the IPN gel with 1.0 % AX exhibited a homogeneous and complete network structure even after intestinal digestion, which explained the reason for the highest encapsulation efficiency and lowest release ratios of RF.

Photopolymerizable Ionogel with Healable Properties Based on Dioxaborolane Vitrimer Chemistry.

Ionogels are solid polymer gel networks loaded with ionic liquid (IL) percolating throughout each other, giving rise to ionically conducting solid electrolytes. They combine the mechanical properties of polymer networks with the ionic conductivity, non-volatility, and non-flammability of ILs. In the frame of their applications in electrochemical-based flexible electronics, ionogels are usually subjected to repeated deformation, making them susceptible to damage. It appears critical to devise a simple and effective strategy to improve their durability and lifespan by imparting them with healing ability through vitrimer chemistry. In this work, we report the original in situ synthesis of polythioether (PTE)-based vitrimer ionogels using fast photopolymerization through thiol-acrylate Michael addition. PTE-based vitrimer was prepared with a constant amount of the trithiol crosslinker and varied proportions of static dithiol spacers and dynamic chain extender BDB containing dynamic exchangeable boronic ester groups. The dynamic ionogels were prepared using 50 wt% of either 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide or 1-Ethyl-3-methylimidazolium trifluoromethanesulfonate, both of which were selected for their high ionic conductivity. They are completely amorphous (Tg below −30 °C), suggesting they can be used at low temperatures. They are stretchable with an elongation at break around 60%, soft with Young’s modulus between 0.4 and 0.6 MPa, and they have high ionic conductivities for solid state electrolytes in the order of 10−4 S·cm−1 at room temperature. They display dynamic properties typical of the vitrimer network, such as stress relaxation and healing, retained despite the large quantity of IL. The design concept illustrated in this work further enlarges the library of vitrimer ionogels and could potentially open a new path for the development of more sustainable, flexible electrochemical-based electronics with extended service life through repair or reprocessing.

Nanoemulsions with sea buckthorn oil and κ-carrageenan

The structure, stability, and rheological properties of nanoemulsions with droplets of sea buckthorn oil stabilized with Tween 80 and Span 80 and κ-carrageenan in the aqueous phase were investigated. The fast flocculation and coalescence of oil droplets occurred in nanoemulsions without κ-carrageenan. The nanoemulsion stability was significantly improved in the presence of the gel network at κ-carrageenan concentrations ≥ 0.5 mass%. TEM analysis showed that oil droplet flocs were trapped in the polymer gel network, so the further floc compaction and creaming were prevented. Nanoemulsions without κ-carrageenan and 0.25 mass% κ-carrageenan displayed the Newtonian-like rheological behavior whereas nanoemulsions with 0.5–5.0 mass% κ-carrageenan demonstrated the non-Newtonian flow of the pseudoplastic type. Oscillatory measurements showed that the values of G′ were higher than the corresponding G″ for nanoemulsions with 0.5 and 2 mass% κ-carrageenan in the investigated range of angular frequencies. However, the G′/G″ crossover was detected for nanoemulsion with 5 mass% κ-carrageenan. The structure relaxation was not observed for this nanoemulsion because the gel in the aqueous phase was irreversibly broken under shear. In nanoemulsions with lower κ-carrageenan concentration, the disintegrated structure was recovered with time after shearing. Apparently, the destruction of the oil droplet flocs under the shear was reversible and the elastic structure of the gel was not destroyed.

Functional gel cathode strategy to enhance the long-term cyclability of the lithium-polysulfide full cell

Lithium-polysulfide (Li-PS) semiflow battery always suffers from a series of drawbacks such as low utilization of active material, inevitable shuttle effect and severe Li corrosion. Herein, a novel PS gel cathode integrating a functional polymer gel network into carbon cloth as the supporting matrix is proposed, in which large quantities of PS species are effectively preserved in the cathode with negligible migration and shuttle. Moreover, the ionically/electronically conductive matrix achieves accelerated redox conversion of the PSs and effective regulation for the nucleation/growth of lithium sulfide. Consequently, the increased reversible capacity, sustainable long-term cycling stability and superior rate capability are demonstrated in the unique cell configuration.

New fat replacement agent comprised of gelatin and soluble dietary fibers derived from date seed powder in beef burger preparation

New forms of composite gels were generated from date seed soluble dietary fiber (SDF) and gelatin. Gelatin-SDF gels' mechanical and functional characteristics were investigated. These gels were used to make low-fat hamburgers. In comparison to control groups (10% and 20% fats), the impact of the SDF-gelatin composite gels on chemical composition, technical parameters, and textural and sensory characteristics was assessed. The results of textural analysis, swelling ratio, water-holding capacity, and freeze-thaw stability revealed that composite gels had the potential to provide unique functional gels, which is beneficial for formula product development. The addition of composited gels raised the moisture, ash, protein, Na, and Ca content of the burger. Furthermore, the composited gels had a significant influence on the L*(brightness), a*(redness), and b*(yellowness) parameters of the hamburger. The composited gels softened and chewed the burger while increasing its springiness. Interpenetrating polymer network (IPN) gels made of SDF and gelatin were effectively used as a fat substitution in meat manufacturing with greater health advantages.

The influence of network architecture on the large deformation and fracture behavior of emulsion-filled gelatin gels

• Emulsion-filled gelatin gels were prepared with contrasting network architecture. • Structure of heterogeneous gels defined by droplet-rich, protein dense domains. • Stress-strain response was correlated to network interactions and architecture. • Fracture mechanics were dependent on network structure and interfacial interactions. • Homogeneous rigid network behaved as rigid scaffold in continuous gel network. This work addresses the effect of network architecture on the large deformation mechanical properties of whey protein-stabilized emulsion-filled gelatin gels as a fat- or oil-filled composite food matrix. Electrostatic interactions were used to induce either a homogeneous (pH 6) or heterogeneous (pH 4) network architecture; the latter was characterized by droplet-rich, protein dense domains embedded in the continuous polymer gel network. Homogeneous gels displayed a transition from strain hardening to strain softening with increasing filler content. In contrast, the formation of a heterogeneous network caused a transition from strain hardening to a linear stress-strain response up to brittle fracture. Fracture mechanics of the homogeneous gels were dominated by imperfect interfacial adhesion and filler-filler contacts under compression. A decrease in fracture strain and fracture stress was caused by interfacial strain amplification and filler debonding. These effects were balanced by filler-filler contacts which produced an increase in fracture stress and strain, particularly for fat-filled gels. In the heterogeneous gels, the more rigid, viscous nature of the droplet-rich domains decreased fracture strain but increased fracture stress as they became the dominant load-bearing structure. The lipid physical state had a marginal impact on fracture strain, while an increase in gelator concentration reduced the observed increase in fracture stress.This work demonstrates that filler/matrix interactions can be used to modulate network structure in emulsion-filled protein gels, which in turn play a strong role in determining the large deformation behavior and fracture mechanics of the composite material.

Salt partitioning in ionized, thermo-responsive hydrogels: perspective to water desalination.

Charged hydrogels are capable of swelling in aqueous salt solutions, whereby part of the salt ions is repelled due to the presence of fixed charged groups inside the hydrogel. This effect creates a concentration gradient between the absorbed solution and the surrounding fluid known as salt partitioning, offering a potential for these materials to be employed to desalinate saltwater. If the charged hydrogels are thermo-sensitive as well, then the purer, absorbed solution can be recovered by shrinking the hydrogels upon temperature change. To tailor that potential in water-purification and desalination applications, the main parameters influencing the salt partitioning, the deswelling of the hydrogels, and the recovery of water must be understood. In this paper, we analyze these factors based on equations derived from the Donnan theory. In addition, hydrogels composed of N-isopropyl acrylamide and acrylic acid are synthesized, and their salt rejection efficiency in a model desalination experiment is studied. A comparison of the experimental and the theoretical results demonstrates that the charge density of the hydrogels at their equilibrium swelling and the degree of water recovery are two parameters controlling the salt rejection efficiency. These parameters are individually controlled by the content of the ionic groups and the degree of cross-linking of the gel polymer network. In addition, the prediction of the theory and the experimental results demonstrate that the salt rejection efficiency can be significantly improved if a second water recovery step is performed by a secondary increase in the temperature in the deswelling process.

Component compatibility influences radiation stability of low temperature cured gels based on PDMS

Transparent low-temperature cured gels were prepared using PDMS-DGE, a selected amine (DAP, DETA, and TAEA) and up to 30% of an organic liquid component – ethanol, t-butanol, or benzene. A mixture of the components was kept at 50 °C long enough to ensure completion of reaction that involves opening of diglycidyl ether (DGE) group and formation of an isopropanol-amine link. Hansens solubility parameters (HSP) were used to explain the influence of compatibility of PDMS, amine used for curing, and a liquid component. The properties and radiation stability (D = 50 kGy, γ-radiation) of obtained gels were studied using impedance spectroscopy, Soxhlet extraction, thermal analysis and ATR-FTIR spectroscopy. Even though amine segments are a minor component of a polymer gel-network, they had major influence on gel properties while liquid component was of secondary importance. The most stable were the gels prepared with a branched triamine, TAEA, regardless of the liquid components. Diamines DAP and particularly DETA produced soft and less stable gels. Influence of liquid components depended on the difference of its solubility parameters to that of both PDMS and the amine used for curing. In ATR-FTIR spectra of most of the irradiated gels amide absorption was observed. It indicates degradation at the isopropanol-amine link. However, no overall degradation was observed in those gels. So called “dangling chains” may have formed and remain entangled in the gel-network. Additionally, free-radicals formed in the PDMS segment of polymer network likely crosslinked thus compensating for degradation at isopropanol-amine links what contributed to stability specially of PDMS-TAEA gels.

Spatial and temporal diffusion-control of dynamic multi-domain self-assembled gels.

The dynamic assembly of a pH-responsive low-molecular-weight gelator (LMWG) within the pre-formed matrix of a second LMWG has been achieved via diffusion of an acid from a reservoir cut into the gel. Self-assembly of the acid-triggered LMWG as it converts from micellar aggregates at basic pH into gel nanofibers at lower pH values can be both spatially and temporally controlled. The pH-responsive LMWG has an impact on the stiffness of the pre-formed gel in the domains in which it assembles. When low acid concentrations are used, LMWG assembly is transient – after the initial proton diffusion phase, the pH rises and disassembly occurs as the system equilibrates. Re-application of additional acid as ‘fuel’ can then re-assemble the LMWG network. Using glucono-δ-lactone (which slowly hydrolyses to gluconic acid) instead of HCl gives slower, more spatially-restricted assembly, and creates longer-lasting pH gradients within the gel. The presence of an agarose polymer gel network improves the mechanical strength of the gels and appears to slightly enhance the rate of proton diffusion. More sophisticated reservoir shapes can be cut into these more mechanically robust gels, enabling the creation of diffusion waves with different geometries, and hence different patterns of LMWG activation. Multiple reservoirs can be used to create overlapping proton diffusion waves, hence achieving differentiated pH patterns in the gel. Using acid diffusion in this way within gels is an intriguing and powerful way of dynamic patterning. The ability to temporally-evolve spatially-resolved patterns using biocompatible weak acids, and the change in rheological performance of the triggered domains, suggest potential future applications of this strategy in tissue engineering.

Basalt/Polyacrylamide‐Ammonium Polyphosphate Hydrogel Composites for Fire‐Resistant Materials

AbstractHydrogels containing a large amount of water are widely used as fire‐resistant materials. However, when exposed to fire, the organic polymer network of gel will burn in a short time as the contained water evaporates. For that, the fire‐retarding ammonium polyphosphate (APP) and woven basalt fibers are introduced in polyacrylamide (PAAm) hydrogels to improve the fire‐resistant performance. Thermo‐gravimetric tests indicating that the APP can prevent gel from decomposition effectively when the content is larger than 13 wt%. And the APP can form a foam layer on gel surface to protect it from burning. The basalt fibers are capable of absorbing heat and strengthening the gel. With the synergetic of APP and basalt fibers, the resultant basalt/PAAm‐APP composite with high mechanical strength exhibits excellent fire‐resistant performance. It can sustain the 1300 °C flame for as long as 15 min.