γ–聚谷氨酸/海藻酸钠双网络水凝胶的制备及性能研究

采用两步法合成了γ–聚谷氨酸（PGA）/海藻酸钠（SA）双网络水凝胶,其中化学交联的PGA–Ly（赖氨酸）网络作为第一网络,而离子交联的SA–Ca2＋网络作为第二网络。通过控制水凝胶的弹性张力和溶胀率之间的平衡,很好地控制了PGA/SA水凝胶的溶胀。通过傅里叶变换红外光谱（FTIR）对水凝胶结构进行了表征。压缩试验结果表明,PGA/SA水凝胶的压缩模量（0.17 MPa）为PGA水凝胶（0.034MPa）的5倍。拉伸试验结果显示,当SA质量浓度达到0.02 g/m L时,PGA/SA水凝胶的断裂伸长率和拉伸强度分别为PGA水凝胶的2倍和8倍。溶胀试验结果表明,随SA含量增加,水凝胶溶胀率逐渐下降。这些特性表明PGA/SA水凝胶在组织工程中具有巨大的应用潜力。     

活性炭对聚丙烯酸水凝胶pH敏感性的影响

以丙烯酸(AA)为单体、活性炭(AC)为惰性致孔剂、N,N-亚甲基双丙烯酰胺为交联剂、过硫酸铵为引发剂,采用自由基溶液聚合法制备了聚丙烯酸(PAA)/AC复合水凝胶,并研究了AC的引入对PAA水凝胶pH敏感性的影响以及不同pH值的缓冲液中水凝胶的溶胀动力学。结果表明:AC的引入并未影响PAA水凝胶的化学组成和热稳定性,但增大了其孔隙尺寸;AC的引入提高了PAA水凝胶的pH敏感性;冻干的PAA/AC复合水凝胶比烘干的PAA/AC复合水凝胶达到溶胀平衡的速率更快、平衡溶胀比更大。     

高弹性自愈水凝胶(C3H5O)1CB[7]/PAA的制备及性能

用丙烯氧基七元瓜环（（C₃H₅O）₁CB[7]）替代传统的交联剂N,N-亚甲基双丙烯酰胺（BIS）制备了新型丙烯氧基七元瓜环/聚丙烯酸凝胶（（C₃H₅O）₁CB[7]/PAA gel）,该凝胶具有高弹性和自愈性。采用IR和¹H NMR技术对其结构进行表征,研究了该水凝胶的溶胀、力学性能,宏观观察了其自愈性能。结果表明：（C₃H₅O）₁CB[7]/PAA gel的网络形成作用力主要是多重氢键;在丙烯酸（AA）17.2%,水82.1%,（C₃H₅O）₁CB[7]0.33%,过硫酸钾（KPS）0.33%时该水凝胶具有良好的自愈性及力学性能,其最大伸长量为105.6 cm,为原长的86倍,弹性模量0.39 kPa,平衡溶胀率是600%。该水凝胶有望成为一种潜在的生物组织工程材料。     

含六碳烷基季铵盐聚合物水凝胶的溶胀性能研究

采用紫外辐照方法,以简单易得的丙烯酸二甲胺基乙酯（DMAEA）、正溴己烷为原料,制得丙烯酰氧乙基二甲基己基溴化铵（6CQ）,其与2-羟基乙基丙烯酸酯（HEA）反应,制备了四种6CQ与HEA质量比不同的丙烯酸羟乙酯-co-丙烯酰氧乙基二甲基己基溴化铵p（HEA-co-6CQ）季铵盐型水凝胶（命名为N9010,N8020,N7030,N6040）。通过FTIR与1HNMR确证了产物结构。考察了温度、时间及电解质浓度对溶胀行为的影响。结果表明,四种水凝胶中,N6040溶胀性能较好,在5 h即可达溶胀平衡,且在10-50℃时溶胀率无明显变化,对温度依赖性不强;溶胀时间对四种水凝胶溶胀率略有影响,但基本在4 h可以达到溶胀平衡;电解质溶液对水凝胶影响比较大,四种水凝胶的溶胀率均比在去离子水中明显降低。热重分析表明,该类水凝胶样品在低于230 ℃环境温度下非常稳定。     

聚丙烯酸/氧化石墨烯自修复水凝胶的合成及性能

通过改进的Hummers方法成功制备了氧化石墨烯(GO)。以Fe3+为交联剂、丙烯酸(AA)为单体、GO为增强剂,采用原位聚合法制备了聚丙烯酸(PAA)/GO自修复水凝胶。考查了不同GO含量下,PAA/GO自修复水凝胶的溶胀性能,并探讨了GO含量、Fe3+含量和H2O含量对PAA/GO自修复水凝胶力学性能的影响,研究了PAA/GO自修复水凝胶的自修复性能。结果表明,Fe3+含量、GO含量和H2O单体含量分别为0.5 %（摩尔分数）、0.5 %（质量分数,下同）、80 %时,具有最佳力学性能（其拉伸强度为743.5 kPa,断裂伸长率为2940.5 %）;GO含量为0.25 %时,PAA/GO自修复水凝胶的吸水性能最大;PAA/GO自修复水凝胶具有优异的自修复性能。     

PAM/SA/CNFs复合水凝胶的制备与性能研究

通过溶液交联聚合法制备了聚丙烯酰胺(PAM)/海藻酸钠(SA)/纤维素纳米纤维(CNFs)半互穿网络结构复合水凝胶。研究了不同添加量的CNFs对SA/PAM/CNFs复合水凝胶的溶胀性能和力学性能的影响;并测定了该复合水凝胶对亚甲基蓝染料的吸附性能。结果表明:当CNFs添加量为0.1ω/%时,复合水凝胶对亚甲基蓝染料的吸附效果最好,且平衡溶胀度最大为9.47,复合水凝胶压缩应力达到114.64 kPa。     

BES-Na磺酸型聚氨酯复合水凝胶的制备与性能研究

以N,N-双(2-羟乙基)-2-氨基乙磺酸钠(BES-Na)和二羟甲基丙酸(DMPA)为亲水扩链剂,原位聚合制备了一系列磺酸型水性聚氨酯(SWPU);再将丙烯酰胺(AM)引入SWPU中乳液聚合制备了一系列BES-Na磺酸型聚氨酯复合水凝胶(SWPUH)。采用傅里叶变换红外光谱(FTIR)表征了SWPUH的结构,研究了BES-Na含量对SWPUH水凝胶的溶胀性能、p H敏感性、离子强度敏感性以及力学性能的影响。结果表明,SWPUH6溶胀比最大,为33. 12,且较SWPUH1平衡溶胀比提升了50. 20%; SWPUH水凝胶还具有多重敏感性,BES-Na的加入能改善水凝胶的酸碱稳定性,且在不同离子强度溶液中,仍然具有较高的溶胀性能。另外,SWPUH水凝胶还具有优异的力学性能,其中SWPUH6水凝胶压缩强度达到最大3. 42 MPa,较SWPUH1压缩强度提升了约4. 5倍,拉伸强度最大值为0. 33 MPa,断裂伸长率最大达到了774%,相比SWPUH1分别提升了175%和59. 3%。     

BES-Na磺酸型聚氨酯复合水凝胶的制备与性能研究

以N,N-双(2-羟乙基)-2-氨基乙磺酸钠(BES-Na)和二羟甲基丙酸(DMPA)为亲水扩链剂,原位聚合制备了一系列磺酸型水性聚氨酯(SWPU);再将丙烯酰胺(AM)引入SWPU中乳液聚合制备了一系列BES-Na磺酸型聚氨酯复合水凝胶(SWPUH)。采用傅里叶变换红外光谱(FTIR)表征了SWPUH的结构,研究了BES-Na含量对SWPUH水凝胶的溶胀性能、p H敏感性、离子强度敏感性以及力学性能的影响。结果表明,SWPUH6溶胀比最大,为33. 12,且较SWPUH1平衡溶胀比提升了50. 20%; SWPUH水凝胶还具有多重敏感性,BES-Na的加入能改善水凝胶的酸碱稳定性,且在不同离子强度溶液中,仍然具有较高的溶胀性能。另外,SWPUH水凝胶还具有优异的力学性能,其中SWPUH6水凝胶压缩强度达到最大3. 42 MPa,较SWPUH1压缩强度提升了约4. 5倍,拉伸强度最大值为0. 33 MPa,断裂伸长率最大达到了774%,相比SWPUH1分别提升了175%和59. 3%。     

八（乙酰苯基）笼形倍半硅氧烷

西南科技大学的孟二辉等人以八苯基多面低聚倍半硅氧烷（OPS）为底物，无水三氯化铝为催化剂，经傅-克酰基化反应合成了笼形八（乙酰苯基）倍半硅氧烷（OAcPS）。较佳的合成条件为：二氯甲烷用量140mL，     

空心玻璃微珠对聚丙烯酸水凝胶溶胀性能的影响

为了研究空心玻璃微珠(HGM)的加入对合成聚丙烯酸(PAA)水凝胶的吸水溶胀性、耐盐性及pH敏感性的影响,以丙烯酸(AA)为单体、聚乙二醇为有机致孔剂、HGM为无机致孔剂、过硫酸铵为引发剂、N,N-亚甲基双丙烯酰胺为交联剂,通过自由基溶液聚合制备了5种不同HGM投料量的PAA水凝胶,并对其结构、热稳定性、表面形貌以及其在纯水、生理盐水和pH缓冲液中的溶胀行为进行了表征。结果表明,HGM的加入并不影响PAA水凝胶的化学组成和热稳定性,但有利于凝胶致孔;适量HGM的加入有助于大幅提高PAA水凝胶的吸水溶胀性、耐盐性和pH敏感性;当HGM的投料量为单体AA质量的10%时,PAA水凝胶的孔结构最丰富,其吸水平衡溶胀比可达345 g/g,吸盐水平衡溶胀比为47 g/g,pH敏感性在5种水凝胶中最佳。     

Janus POSS-based hydrogel electrolytes with highly stretchable and low-temperature resistant performances for all-in-one supercapacitors

Conductive hydrogels can be utilized in the field of flexible supercapacitors due to their stretchable properties and high ionic conductivity. However, many of the conductive hydrogels lose their stretchability and conductivity at subzero temperatures. Herein, a novel Janus POSS-based hydrogel electrolyte that shows excellent flexibility and ionic conductivity at low temperatures is designed and prepared by the copolymerization of acrylamide and a water-soluble Janus-type polyhedral oligomeric silsesquioxane (AS-POSS) containing sodium sulfonate groups and double bonding groups. The sodium sulfonate groups of AS-POSS and LiCl endow the hydrogel electrolyte with excellent anti-freezing ability. Simultaneously, the double bonding groups of AS-POSS enable a successful POSS crosslinking in the polymer network, resulting in a highly stretchable hydrogel electrolyte (1445%) with high ionic conductivity (0.067 S cm⁻¹) at −20°C. Thereafter, the all-in-one flexible supercapacitor is prepared by in-situ polymerization of aniline. Based on the exceptional anti-freezing properties of the Janus POSS-based hydrogel electrolyte, the all-in-one supercapacitor exhibits stable electrochemical performance (>90% capacitance retained under deformation at −20°C) and excellent cycling stability (only 19.7% capacitance decay over 2000 charge/discharge cycles at −20°C) at low temperatures. The Janus POSS-based hydrogel electrolyte is expected to be a promising gel electrolyte for an all-in-one supercapacitor that resists freezing.     

Water sorption behavior of CMC/PAM hydrogels prepared by γ-irradiation and release of potassium nitrate as agrochemical

Novel types of highly swelling CMC/PAM hydrogels have been prepared by grafting cross-linked polyacrylamide (PAM) chains onto carboxymethylcellulose (CMC) via a free radical polymerization method using γ-irradiation. The prepared CMC/PAM hydrogels were characterized by FT-IR spectral analysis. The AM content and irradiation dose had a direct effect on gel content of CMC/PAM hydrogels and inverse effect on their swelling ratio. The hydrogels showed enormous swelling in aqueous medium and displayed swelling characteristics which were highly dependent on the chemical composition of the hydrogel, pH and ionic strength of the medium in which the hydrogel was immersed. The results were supported by morphological properties of CMC/PAM hydrogels by using SEM. The kinetics of water uptake and the water transport mechanism were studied as a function of the CMC/AM ratio into the prepared hydrogel. The release rate of potassium nitrate entrapped within the CMC/PAM matrix increased by enhancing its loading %, and decreased with lowering AM content and irradiation dose.     

Fabrication of tough,self-recoverable,and electrically conductive hydrogels by in situ reduction of poly(acrylic acid) grafted graphene oxide in polyacrylamide hydrogel matrix

Developing electrically conductive hydrogels with good electronic properties and excellent mechanical performance is significant to their potential applications. In this article, we present a strategy to fabricate tough, self-recoverable and electrically conductive hydrogels containing reduced graphene oxide (rGO). Poly(acrylic acid) grafted graphene oxide (GO-g-PAA) was synthesized and incorporated into chemically crosslinked polyacrylamide (PAM) networks to obtain GO-g-PAA/PAM hydrogels, which were further treated with ascorbic acid solution at ambient temperature to give rGO-g-PAA/PAM hydrogels. The interfacial interaction between GO/rGO and hydrogel matrix was improved by reversible hydrogen bonds between the grafted PAA chains and PAM matrix. Consequently, both GO-g-PAA/PAM and rGO-g-PAA/PAM hydrogels exhibited improved tensile properties, excellent energy dissipation, and rapid self-recovery. The in situ chemical reduction of GO-g-PAA in hydrogel matrix endowed rGO-g-PAA/PAM hydrogels with satisfactory electrical conductivity and obvious resistance change upon stretching. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48781.     

Preparation of a novel pH-sensitive hydrogel based on acrylic acid and polyhedral oligomeric silsesquioxane for controlled drug release of theophylline

Hydrogels based on pH-sensitive polymers are of great interest as potential biomaterials for the controlled delivery of drug molecules. In this study, a novel pH-sensitive copolymer hydrogel based on acrylic acid (AA) monomer by free-radical solution polymerization were synthesized with organic–inorganic cross-linking agent of octavinyl polyhedral oligomeric silsesquioxane (OVPOSS). And its properties were compared with conventional hydrogels using N,N′-methylenebisacrylamide (MBA) as cross-linking agent. The copolymers were characterized by Fourier transform infrared spectra and differential scanning calorimetry. The morphology after swelling was presented by scanning electron microscopy. Swelling behaviors in different pH and potential applications in controlled drug delivery of the hydrogels were also examined. The results showed that both hydrogels were pH sensitive. However, as the addition of OVPOSS limited the movement of the molecular chain segment, the swelling ratio and the drug-release rate of theophylline in SGF decreased obviously when using OVPOSS as cross-linking agent, comparing with P(MBA-co-AA) hydrogels. The results in this study suggested that P(OVPOSS-co-AA) could serve as potential candidate for theophylline drug delivery.     

Synthesis,pH sensitivity,and drug‐release behavior of acrylic acid and polyhedral oligomeric silsesquioxane copolymer

pH‐Sensitive organic–inorganic copolymers of hydrogels were developed as drug delivery systems (DDS) to improve the swelling behavior of polyacrylic acid (PAA). They were represented through FTIR, TGA and XRD characterization which revealed that the functional groups of methacryl‐phenyl polyhedral oligomeric silsesquioxane (POSS) were successfully added to the acrylic acid (AA) molecular chains through radical solution polymerization. The DSC test results indicate that the addition of POSS could improve the thermal properties of the copolymers. The swelling properties at the pH range of 1.25–8.01 exhibited the pH sensitivity of POSS/AA copolymers (POSS‐co‐AA) and the lower swelling ratio in acidic conditions indicated that the DDS had low amount of release in SGF; this phenomenon suggested that the copolymer was available as DDS of theophylline. And it was proved by drug release curve and scanning electron microscopy. Since the addition of POSS reduced the release rate of theophylline and prolonged the release time of the drug, the concentration range of theophylline could remain low for an extended duration. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

A novel temperature and pH dual‐responsive hybrid hydrogel with polyhedral oligomeric silsesquioxane as crosslinker: synthesis,characterization and drug release properties

Octavinyl polyhedral oligomeric silsesquioxane (OVPS) is used as the crosslinker instead of N,N′‐methylenebisacrylamide (BIS) to copolymerize with 2‐(dimethylamino)ethyl methacrylate (DMAEMA) or DMAEMA and N‐isopropylacrylamide (NIPAM) to prepare hybrid hydrogels: P(OVPS‐co‐DMAEMA) and P(OVPS‐co‐DMAEMA‐co‐NIPAM). The prepared hydrogels are transparent and show dual response to temperature and pH. The hydrogels were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis and tensile tests. Their mechanical properties, swelling ratio, deswelling and reswelling behaviors as well as drug release properties were investigated. The results indicate that OVPS can be incorporated into polymer networks in proportion to feed ratios. The P(OVPS‐co‐DMAEMA) hydrogel exhibits more homogeneous interior structure, higher swelling ratio and faster response than the conventional hydrogel prepared with BIS. Moreover, the incorporation of OVPS enhances the compression and tensile properties of the hydrogels. The feed ratios of OVPS and NIPAM have a great effect on volume phase transition temperature, thermal sensitivity, swelling behavior, mechanical properties and drug release properties of the hybrid hydrogels. The prepared dual‐responsive OVPS‐containing hydrogels are expected to be used as biomedical materials in drug release and tissue engineering. © 2014 Society of Chemical Industry     

Synthesis of polyhedral oligomeric silsesquioxane nano‐crosslinked poly(ethylene glycol)‐based hybrid hydrogels for drug delivery and antibacterial activity

The synthesis is reported of novel hybrid hydrogels based on ethylenediaminetetraacetic acid dianhydride and poly(ethylene glycol) (PEG) with octa‐aminopropyl polyhedral oligomeric silsesquioxane hydrochloride salt (OA‐POSS) as a nano‐crosslinker under solvent‐free conditions. The molecular weight of PEG was varied between 600 and 1000 Da. The synthesized hydrogels were characterized using various techniques. Further, the swelling behavior and antibacterial activity of the hydrogels and release kinetics of metronidazole (MTZ) as a model drug from them were evaluated. Experimental results demonstrate that hydrogels with tunable properties can be synthesized by varying the PEG molecular weight and type of crosslinker (hybrid or organic). Among the synthesized hybrid hydrogels, that crosslinked by OA‐POSS with long PEG chains (1000 Da) showed the highest swelling degree (2000%), drug encapsulation efficiency (88%) and extent of MTZ release (96%). © 2018 Society of Chemical Industry     

One-pot preparation of ultrastrong double network hydrogels

A double-network (DN) polyethylene glycol/polyacrylic acid (PEG/PAA) hydrogel with high compressive strength was synthesized by one-pot solution polymerization. The PEG network crosslinked by glutaraldehyde (GA) was fabricated via condensation reaction while the PAA network crosslinked by N,N’-dimethylenebiacrylamide (MBAM) via free-radical polymerization. The components of hydrogel were analyzed with Fourier transform infrared spectroscopy (FTIR). Mechanical strength of PEG/PAA hydrogels was examined, and the results showed that the addition of GA and PEG endowed the DN hydrogel with a high compressive strength of 10.9 MPa in a water content of 90 wt% due to lightly crosslinking and special entangled bundles morphology. Morphological studies showed that the hydrogels exhibited various pore structures when they were synthesized using different molar ratio of GA to PEG. This work provided a simple way to prepare ultrastrong DN hydrogels.     

Synthesis and characterization of superabsorbent hydrogels composites based on polysuccinimide

A kind of novel superabsorbent hydrogel with high swelling ratio property that could be used for the development of water absorbing resin, soil water retention agent, and chemical sand‐fixing material was synthesized in this study. The hydrogels were prepared by the crosslinking reaction of polysuccinimide (PSI). The relationships between swelling ratio and volume of solvent as well as the concentration of crosslinking agent were investigated in detail. Several composites, such as starch, carrageenan, and polyacrylamide, were added into hydrogels to enhance the swelling ratio. It was found that the swelling ratio was significantly increased, which the maximum water absorbency was enhanced 2.46 times when the composite polyacrylamide (PAM) was added compared to the control. The effects of ionic strength and sensitivity of pH on hydrogels were also studied. The modified hydrogels products with swelling ratio less sensitivity to the salinity as well as relative high swelling ration in salinity system were also obtained by adding PAM. Through the Fourier transform infrared spectroscopy (FTIR) characterizations, the crosslinking reaction mechanism and the structure of composite were proposed. In addition, the transmission electron microscopy (TEM) examinations showed that some composite materials elevated the physical crosslinked and connected channels density substantially. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 550–557, 2006     

Swelling-induced surface instability of a hydrogen-bonded LBL film and its self-healing

Thin hydrogel films attached to a rigid substrate can only swell along the direction perpendicular to the substrate, which generates compressive stress within the gel. When the stress is sufficiently large, the free surface of the gel will locally buckle and fold against itself to form various wrinkling patterns. Here we show that hydrogen-bonded layer-by-layer (LBL) films of poly(vinyl pyrrolidone) (PVPON) and poly(acrylic acid) (PAA) also swell in ethanol/water mixtures. Like ordinary hydrogel films attached to a substrate, the LBL films also undergo mechanical instability when their swelling degree is large enough. By adjusting the composition and pH of the ethanol/water mixture, the swelling degree of the film can be adjusted, which further decides whether the mechanical instability occurs or not. Like ordinary hydrogel films, the surface wrinkling of the PVPON/PAA films occurs via a nucleation-growth process. Unlike ordinary hydrogels, the critical swelling degree for the onset of wrinkling for PVPON/PAA films increases with increasing film thickness. More importantly, the wrinkling patterns can be healed automatically, because the transient network of PVPON/PAA films allows for the relief of compressive stress via its rearrangement. The phenomenon observed here may provide a possible way to erase the undesired wrinkling patterns on constrained hydrogel films.