Hybrid Gels Research Articles

Mixing-to-Answer Iodide Sensing with Commercial Chemicals.

We develop a convenient, colorimetric assay (Au/PEI) for rapid iodide (I-) determination that can be prepared facilely by mixing commercially available chemicals including tetrachloroauric acid (HAuCl4) and poly(ether imide) (PEI), and the assay can be carried out directly by adding the samples to the assay without any pretreatment and additional procedure. Au/PEI operates on the principle that I- accelerates the formation of Au NPs, which leads to a visible color change from light yellow to red for naked-eye readout with high specificity. We integrate our assay on solid devices including gel hybrids (Au/PEI/GH) and filter paper (Au/PEI paper) to satisfy the demand of point-of-care testing and justify the practicality by detecting I- in lake water that was supplemented with 10, 20, or 40 μM of I-. Au/PEI/GH with the limit of detection of 0.35 μM can satisfy the detection of drinking water based on the guidelines (1.2 μM) set by the Chinese government, and Au/PEI paper can be used even after 1 year of storage. Such assays provide a convenient and straightforward choice for routine, on-site I- tests.

Facile fabrication of photoinduced superhydrophobic–superhydrophilic surfaces on cellulose substrate without strength loss

A novel strategy was reported on the design and fabrication of functional photosensitive hybrid sols (FPHSs) by non-alcoholic emulsification in the presence of a TiO2 nanoparticle and photoinitiator via a sol-gel process using tetraethylorthosilicate, γ-methacryloxypropyltrimethoxysilane (MPS) and hydrophobic silane coupling agents as precursors. Smart cellulose substrates with alterable superhydrophobic–superhydrophilic conversion were fabricated using FPHS via the ultraviolet (UV) curing process. The liquid FPHS was photocured into solid gel during UV irradiation for 40 s with MPSs in FPHS, which was verified via Fourier transform infrared spectra. The cellulose substrates were modified with FPHSs, and the water contact angles of the modified cellulose substrates were more than 150°. The superhydrophobicity was improved by the gathering of hydrophobic chains and particle deposition of hybrid gel on the fiber surface. Nevertheless, the water contact angles of the modified cellulose substrates were receded with UV irradiation from 158° to 0° in 200 min, due to TiO2 photoinduction. The irradiated cellulose substrates were placed in the dark, and the water contact angles were recovered to about 130°, gradually. What is more, the reversible process can be repeated more than eight times. The modified cellulose substrate presented excellent washing fastness, even suffering 10 times washing processing. The mechanical properties, including breaking strength and elongation rate, were improved after the coating and UV curing process, which considerably remedied the defects of the heating curing process on the mechanical properties.

A polyoxometalate gel electrolyte with enhanced electrochemical performance

A novel hybrid gel electrolyte has been synthesized by self-assembling of 1-(3-sulfonic group) propyl pyridine (PyPS) cation and the heteropoly anion. The results of FTIR spectra and XRD patterns indicate the synthesized hybrid gel electrolyte [PyPS]5SiMo[Formula: see text]VO[Formula: see text] possesses lamellar structure with [Formula: see text]-spacing of 2.09[Formula: see text]nm. The electrochemical stability potential window is up to 3[Formula: see text]V. Ionic conductivity of [Formula: see text][Formula: see text]S[Formula: see text]cm[Formula: see text] was observed above the phase transformation temperature under ambient condition. The conductivity enhances with increasing temperatures.

Manipulating Metallogel Properties by Luminogens and Their Applications in Cell Imaging.

Manipulating gelation properties of the isomeric zinc–terpyridine complexes C-1 (nongelator) and C-2 (gelator) using three different luminescent dyes, viz., acridine yellow (AY), ethidium bromide (EB), and azido-boron dipyrromethene, have been described. Hybrid gels created by the combination of C-1, C-2, and above-mentioned dyes have been termed complex-luminogen mixed gels (CLMGs). Ensuing CLMGs have been thoroughly characterized by spectral, morphological, and rheological studies. Cytotoxicity measurements and imaging against breast cancer cell line MDA-MB-231 unveiled that three out of the five CLMGs can be effectively used for cell imaging. Interestingly, direct use of the metal-containing hybrid gels for live cell imaging which is a distinctive approach, has been successfully achieved with significantly encouraging results.

Hybrids of Silica/Poly(caprolactone coglycidoxypropyl trimethoxysilane) as Biomaterials

Bioactive glasses stimulate bone regeneration but are brittle. Biomaterials are needed that share load with bone, promote bone regeneration, and biodegrade at controlled rates. Sol–gel hybrids can achieve this through their intimate inorganic and organic conetworks, depending on the organic polymer used. Polycaprolactone degrades slowly but lacks functional groups for the critical step of covalent coupling to the silica conetwork. Here, we synthesized a novel copolymer of caprolactone and glycidoxypropyl trimethoxysilane through one-pot ring opening polymerization (ROP). Hybrids with different organic content were fabricated using such a copolymer for the first time. The copolymer can directly bond to a silica network due its trimethoxysilane groups, which can hydrolyze, leaving silanol groups that undergo polycondensation with silanol groups of the silica network. The number of repeating units of caprolactone and glycidoxypropyl trimethoxysilane functional groups were controlled via ROP. The mechanical p...

Influence of Divalent Cation on Morphology and Drug Delivery Efficiency of Mixed Polymer Nanoparticles.

Biopolymeric nanoparticles comprising chitosan-alginate have attracted interest in drug delivery due to their protective nature, biocompatibility, biodegradability and hydrophilicity. The present study was designed to encapsulate levofloxacin in chitosan-alginate hybrid gel for controlled release and to evaluate the effect of divalent alkaline earth metal ions (Mg2+, Ca2+, Sr2+, Ba2+) on encapsulation efficiency and drug release kinetics considering their role in polyelectrolyte gelation method. Divalent metal ions control the rigidity and elasticity of the hydrogels and have the ability to change the shape and size of nanostructure formed by chitosan-alginate. The particle size increases and encapsulation efficiency decreases with the size of the divalent ions. Spherical shaped particles were formed by Mg2+ and Ca2+, whereas Sr2+ and Ba2+ produced non-spherical particles. SEM image clearly shows transformation of sphere to truncated tetrahedron by Sr2+ and clear rod shape by Ba2+. Therefore, it is concluded that metal ions have significant influence on the morphology and drug encapsulation and release profile of the chitosan-alginate hybrid polymer nanoparticles.

Rheological properties and microstructure of soy protein isolate /κ-carrageenan gels under high-speed shear treatment

This study investigated the non-linear rheological properties and microstructure of acid-induced gels of Soy Protein Isolate (SPI) and κ-Carrageenan (KARA) subjected to high-speed shear treatment. It is found that, high-speed shear homogeneous (HSH) treatment of SPI molecular made the hybrid gel a stronger and more solid system. The HSH treatment also helps KARA disperse into SPI more uniformly. Hybrid gels conform to the basic characteristics of the typical Type I network structure. After HSH treatment, hybrid gels showed more elastic property. The protein aggregate becomes smaller as the SPI network structure gets more compact, after the gel suffered HSH treatment. HSH treatment also reduced the “phase separation” function of the system to some extent. The complex network structure of SPI/KARA hybrid gel becomes more chaotic under the HSH treatment.

Natural Triterpenoid-Tailored Phosphate: In Situ Reduction of Heavy Metals Spontaneously to Generate Electrochemical Hybrid Gels.

In this work, we reported a biocompatible nature product-based soft material which could convert heavy metals to nanoparticles (NPs) in situ spontaneously in a simple step. We have designed and synthesized a natural triterpenoid-tailored phosphate (methyl glycyrrhetate phosphate (MGP)), and this amphiphilic MGP could form the stable hydrogel and extract gold salt from water, followed by spontaneous in situ AuNP formation without external reductants. Notably, the AuNPs were mainly localized on nanofibers instead of gel cavities, and the resulting MGP-AuNPs hybrid gel exhibited attractive electrocatalytic and conductive properties. In addition, as an efficient leaching extraction agent, MGP hydrogel showed higher affinity toward heavy metals over other common metals on account of the high reduction potential of heavy metals. Our work not only provides a novel yet simple way in generating electrochemical hybrid gels by in situ reduction of heavy metals spontaneously but also expands the application of nature product-based functional materials.

Hybrid Physical Gels from Polymers and Self-Assembled Systems: A Novel Path for Making Functional Materials.

In recent years, the synthesis of novel organic molecules that spontaneously self-assemble into a large variety of molecular architecture, particularly the formation of organogels, has yielded new opportunities in the preparation of functional materials. Here, we present an original preparation path of such materials through the fabrication of hybrid gels of these molecules with covalent polymers. Three types of systems are described: (i) intermingled gels where a polymer gel and an organogel pervade one another; (ii) encapsulation of self-assembled filaments in polymer fibrils, which provides a system with unusual magnetic properties; (iii) the reverse situation in which self-assembled nanotubes sheathe polymer fibrils. Two covalent polymers are considered: a neutral polymer, specifically stereoregular polystyrene (isotactic or syndiotactic), and a semi-conducting polymer, P3BT. In the latter case, semi-conducting nanowires are obtained.

Synthesis and characterization of porphyrin-based porous coordination polymers obtained by supercritical CO2 extraction

H2TCP and ZnTCP (TCP = 5,10,15,20-tetra(4-(phenoxy-4-yl)butanoic acid)porphyrin) were synthesized as gelator, reacted with Al(NO3)3·9H2O and Cr(NO3)3·9H2O by solvothermal and sol–gel method to give four organic–inorganic hybrid gels. The intermediate gels were extracted by supercritical CO2 to remove the redundant solvent molecules (DMF, EtOH) and the unreacted M3+ (M = Al, Cr), the final H2TCP-Al (PCP1), H2TCP-Cr (PCP2), ZnTCP-Al (PCP3), ZnTCP-Cr (PCP4) porous coordination polymers (PCPs) were obtained based on aerogels. The PCPs were characterized by FT-TR, UV–Vis, SEM, TEM and PXRD. Thermal stability and BET tests were carried by TGA and nitrogen sorption measurements. Results show that these PCPs exhibit superior thermal stability, tunable porosity and relative high BET surface ranging from 409 to 454 m2 g−1. Dyes adsorption experiments were performed to evaluate the adsorption capacity to dyes and the PCP3 has the best capacity which is 589 mg g−1 for rhodamine B (RhB) and 595 mg g−1 for methylene blue (MB). This work provides a promising method for the preparation of porous materials by supercritical CO2 extraction and exhibits some considerable applications in dyes adsorption.

Tough and Conductive Hybrid Hydrogels Enabling Facile Patterning.

Conductive polymer hydrogels (CPHs) that combine the unique properties of hydrogels and electronic properties of conductors have shown their great potentials in wearable/implantable electronic devices, where materials with remarkable mechanical properties, high conductivity, and easy processability are demanding. Here, we have developed a new type of polyion complex/polyaniline (PIC/PAni) hybrid hydrogels that are tough, conductive, and can be facilely patterned. The incorporation of conductive phase (PAni) into PIC matrix through phytic acid resulted in hybrid gels with ∼65 wt % water; high conductivity while maintaining the key viscoelasticity of the tough matrix. The gel prepared from 1 M aniline (Ani) exhibited the breaking strain, fracture stress, tensile modulus, and electrical conductivity of 395%, 1.15 MPa, 5.31 MPa, and 0.7 S/m, respectively, superior to the most existing CPHs. The mechanical and electrical performance of PIC/PAni hybrid hydrogels exhibited pronounced rate-dependent and self-recovery behaviors. The hybrid gels can effectively detect subtle human motions as strain sensors. Alternating conductive/nonconductive patterns can be readily achieved by selective Ani polymerization using stencil masks. This facile patterning method based on PIC/PAni gels can be readily scaled up for fast fabrication of wavy gel circuits and multichannel sensor arrays, enabling real-time monitoring of the large-extent and large-area deformations with various sensitivities.

Effect of Gamma Ray Irradiation on Friction Property of Poly(vinyl alcohol) Cast-Drying on Freeze-Thawed Hybrid Gel.

Poly(vinyl alcohol) (PVA) is a biocompatible polymer with low toxicity. It is possible to prepare physically cross-linked PVA gels having hydrogen bonds without using a cross-linking agent. The newly reported physically cross-linked PVA cast-drying (CD) on freeze-thawed (FT) hybrid gel has an excellent friction property, which is expected to be applied as a candidate material for artificial cartilage. Gamma ray sterilization for clinical applications usually causes additional chemical cross-linking and changes physical properties of gels. In this study, CD on FT hybrid gels were irradiated using gamma rays at a different dose rate and irradiance. The results showed the optimized irradiation conditions for gamma irradiated gels to retain excellent friction characteristics.

Crosslinked carboxymethyl cellulose-sodium borate hybrid binder for advanced silicon anodes in lithium-ion batteries

Silicon anodes have drawn ever-increasing attention in lithium-ion batteries (LIBs) owing to their extremely high theoretical capacity and abundance in the earth. Despite promising advantages, the wide use of silicon anodes in LIBs is highly hindered by their fast capacity fading and low Coulombic efficiency arising from their substantial volumetric variation (>300%). Herein, we report a novel aqueous hybrid gel binder for silicon anodes via crosslinking sodium carboxymethyl cellulose (NaCMC) by an inorganic crosslinker-sodium borate. Not only this gel polymer binder can chemically bond to silicon nanoparticle, but also the deformable framework of this crosslinked binder is capable of maintaining electrode integrity, thus buffering dramatic volume change of silicon. Consequently, the silicon anode with this gel binder exhibits good cycle life (1211.5mAh/g after 600 cycles) and high initial Coulombic efficiency (88.95%).

Inorganic/polymer-graphene hybrid gel as versatile electrochemical platform for electrochemical capacitor and biosensor

In this work, we reported the design and synthesis of a new type of polymer-graphene hybrid material by supramolecular self-assembly of polyacrylic acid (PAA) and graphene to form a robust sponge-like PAA-graphene gel (PAA-GG) with internally well-defined porous structure, followed by electrodepositon of high-density and well-dispersed MnO2 nanowires on outer and inner surface of PAA-GG scaffold. The as-obtained MnO2/PAA-GG uniquely combines a series of structural and electrochemical characteristics of its precursors, including large surface area, improved capacitive properties and enhanced electrocatalytic activities, fostering versatile applications as electrochemical capacitor and biosensor. Our results show that the symmetric capacitor assembled by MnO2/PAA-GG electrode presents a specific capacitance of 123 F g−1 under a current density of 0.5 A g−1, and its specific capacitance only loss 13.8% after 5000 cycles. For potential application as electrochemical biosensor, MnO2/PAA-GG exhibits high sensitivity and selectivity in nonenzymatic detection of H2O2. The linear range is between 0.05 mM and 50 mM with a low detection limit down to 10 μM, which enables it to be used for real-time tracking of H2O2 secretion in live cells. These promising features make the inorganic/polymer-graphene hybrid gel attractive for a wide spectrum of applications in energy, electrocatalysis and bioanalytical areas.

Applications of melting gels

Hybrid organic-inorganic gels and glasses have been studied for many years for a variety of applications. Using the sol–gel process, it is possible to prepare silica-based hybrid gels that are rigid at room temperature, but soften and flow around 110 °C. This softening behavior has been called melting, even though it is not melting in a thermodynamic sense. Instead, the ability to flow is an indication that the material is not entirely cross-linked. In fact, some melting gels show glass transition behavior at temperatures below 0 °C. However, once these so-called melting gels have been heated at around 160 °C for 24 h, they no longer show the ability to soften. With an interest in using these materials for sealing microelectronics, their physical properties have been measured. In addition, their hydrophobicity, adhesion and electrochemical response have been evaluated in corrosive environments. It is also found that melting gels have been imprinted with good fidelity, and that gold nanoparticles maintain their plasmonic resonance when dispersed in melting gels. Finally, melting gels have been deposited by electrospraying to produce a variety of textures.

Comparative Study of Hydrogel-Based Recyclable Photocatalysts.

A series of hydrogen-based TiO2 photocatalysts were prepared by the simple entrapment of TiO2 nanoparticles in different hydrogel matrices using gelation processes. The hydrogels, namely, agarose, alginate, and chitosan, were used as matrices for TiO2 immobilization. Morphological differences were characterized for the three different hybrid gel photocatalysts. The rate of methylene blue (MB) photodegradation increased with increasing initial TiO2 dosage in all samples. The structural properties of the hydrogels significantly affected the diffusion of MB and altered the photocatalytic activities. Among these three different hybrid gel photocatalysts, the chitosan-based TiO2 membrane showed superior activity to the agarose- and alginate-based TiO2 hybrid gels. In addition, chitosan/TiO2 still showed excellent photocatalytic activity after being reused in three cycles, suggesting that chitosan/TiO2 is a new potential eco-friendly and a cost-effective photocatalyst for wastewater treatment.

Hybrid gel polymer electrolyte with good stability and its application in electrochromic device

Using propylene carbonate (PC) as solvent, a hybrid gel polymer electrolyte (GPE) based on poly(propyleneglycol) bis(2-aminopropyl ether) (2-APPG) and 3-isocyanatepropyltriethoxysilane (ICS) was successfully synthesized by sol–gel method. The result shows the hybrid gel polymer electrolyte with [O]/[Li] ratio of 22 has a high ionic conductivity, good thermal stability, as well as good electrochemical stability. The ionic conductivities reach as high as 1.43 × 10− 3 S cm− 1 at 30 °C and 3.36 × 10− 3 S cm− 1 at 100 °C, respectively. Nearly 0 weight loss was observed up to 100 °C. The electrochromic device is fabricated by using the hybrid gel polymer as electrolyte. The results demonstrate its high coloration efficiency (267.4 cm2 C− 1) and long cycle life (150 cycles with the linear potential sweep between − 3.5 and + 2.5 V), When the applying voltage is increased to as high as 5 V on the electrochromic device, a fast response is obtained (colored/bleached time are 13/19 s), which indicates its potential application under high voltage conditions.

Fully Printed Flexible Smart Hybrid Hydrogels

AbstractA printable hybrid hydrogel is fabricated by embedding poly(N‐isopropylacrylamide) (PNIPAm) microparticles within a water‐rich silica‐alumina(Si/Al)‐based gel matrix. The hybrid gel holds water content of up to 70 wt%, due to its unique Si/Al matrix. The hybrid hydrogel can respond to both heat and electrical stimuli, and can be directly printed layer‐by‐layer using a commercial 3‐dimensional printer, without requiring any curing. The hybrid ink is printed onto a transparent, flexible conductive electrode composed of silver nanoparticles and sustains bending angles of up to 180°, which enables patterning of various flexible devices such as smart windows and a 3D optical waveguide valve.

P2X7 receptor antagonist delivery vehicle based on photocrosslinked amphiphilic hybrid gels.

We report here a method for the synthesis of a unique hybrid gel system for the sustained delivery of P2X7 receptor (P2X7R) antagonist. P2X7R has been reported as a key mediator in inflammatory processes and controlled delivery of this molecule would be critical for the treatment of inflammatory arthritis. The hybrid gel designed here for the sustained delivery of P2X7R antagonists is based on crosslinked hydrophobic styrene-butadiene-styrene (SBS) polymer as a continuous network, where hydrogel particles prepared with hydrophilic poly(ethylene glycol) (PEG) were embedded into this system. PEG hydrogel particle-incorporated SBS gels were characterized through electron microscopy, water contact angle observations, and strong mechanical properties were confirmed through nanoindentation measurements. The release of P2X7R antagonist from these hybrid hydrogel-elastomer system demonstrated a sustained drug release profile up to 28 days at physiological pH, which was not observed in earlier reports. We obtained drug release percentages ranging from 49.72% to 93.04% which indicated the tunability of release through SBS crosslinking and hydrophilic/hydrophobic nature of SBS. This tunability is significant to achieve simultaneous improvements in drug efficacy with reduced side effects. CellTiter-Glo luminescence measurements using human kidney cells revealed that these networks are non-toxic and highly biocompatible with percent cell viabilities of higher than 85%. The approach presented here with crosslinked, amphiphilic and elastic SBS gel systems is not only promising for extended release of P2X7R antagonist but could also allow for incorporation of different molecules so that simultaneous/sequential and extended release profiles for therapeutic molecules could be achieved.

Ultra-broadband nonlinear optical response of two-dimensional h-BN nanosheets and their hybrid gel glasses.

Hydrophilic hydroxylated hexagonal boron nitride nanosheets (BNNSs), also called 'white graphene', exhibit high water solubility, compatibility, dispersity with physical and/or chemical effects on the gel matrix, and unexpected but outstanding near-infrared adsorption and nonlinear optical limiting properties. These properties mean that hydroxylated BNNSs are suitable for practical applications in solidification and devices. Hydroxylated BNNSs are doped into an organically modified silicate matrix through a facile sol-gel process. The resulting BNNS-organically modified silicate glass hybrids demonstrate various solid structures (glass, coating, and film), good uniformity, thermostability, toughness, and high linear transmittance in the visible and near-infrared regions. Hybrid glasses showed large optical limiting effects and high doping concentrations without the addition of a compatibiliser, and their limiting thresholds and concentration exceed those of the corresponding suspensions by factors of 1.3-2 and 20-130, respectively. The optical limiting performance of BNNSs is almost equal to or may exceed those of graphene oxide and graphene in solutions and doped glasses. The combined mechanisms of nonlinear absorption, refraction, and scattering are deduced. A solid organically modified silicate hybrid transparent system doped with BNNSs is a promising candidate material for optical limiters and nonlinear optical devices. This system could be an efficient solid-state optical limiter in the visible and long-wavelength near-infrared regions (532-2000 nm).