导电水凝胶的制备及应用研究进展

导电水凝胶是一类将亲水性基质和导电介质有机结合的新型水凝胶,具有较高的柔韧性、可调的力学性能和优异的电化学性能,在柔性电子设备等领域具有广阔的应用前景。本文综述了导电水凝胶材料的研究前沿和动态,介绍了导电水凝胶的分类及制备方法,讨论了导电水凝胶的结构设计与性能,重点阐述了导电水凝胶材料的应用研究进展,归纳了导电水凝胶材料面临的问题与挑战,并展望了导电水凝胶材料的发展趋势,指出采用天然可再生资源为原料开发具有高导电性、力学性能稳定、耐极端温度、生物相容性和生物可降解的导电水凝胶将成为下一步研究重点,同时优化柔性电子装置、提高器件输出稳定性也将成为重要的研究方向之一。导电水凝胶的制备及应用研究将促进柔性电子功能材料领域的快速发展。     

环境刺激响应型高强度智能水凝胶研究进展

环境刺激响应型智能水凝胶能够对外界环境因素的变化产生显著的体积或其他特性的变化,且其性质和结构与生物组织类似,有望应用于人工软骨、人造肌肉、组织工程等领域,引起了广泛的关注。提高环境刺激响应型智能水凝胶的力学性能是智能水凝胶应用研究的重要方向之一。本文综述了近年来环境刺激响应型高强度智能水凝胶的研究进展,简述了高强度智能水凝胶的网络结构的构建策略与方法,分析了其具备高力学性能的机理,重点介绍了4类不同结构的高强度智能水凝胶,即超低交联结构水凝胶、纳米颗粒复合水凝胶、拓扑结构水凝胶以及双网络结构水凝胶,最后讨论了环境刺激响应型高强度智能水凝胶在面向应用的研究过程中仍然需要解决的关键科学问题,如智能水凝胶的环境刺激与力学性能的博弈效应以及响应环境刺激前后的力学性能差异等。     

壳聚糖温敏水凝胶研究进展

温敏性水凝胶是一种智能型高分子水凝胶,能在应答外界温度刺激时发生自身相变,具有良好的生物相容性与力学性能,被广泛应用于组织工程、细胞包封、药物传递等方面。壳聚糖是一种在自然界中大量存在的多糖,因具有低细胞毒性与生物相容性,常作为药物缓释体被广泛应用。重点对近几年壳聚糖温敏水凝胶的相关研究进行综述。     

基于天然材料的自愈水凝胶伤口敷料研究进展

目前使用的伤口敷料中，水凝胶因其可改变的、优异的化学、物理和生物特性以及具有能够吸收和保留大量水分的三维交联聚合物网络而被广泛研究应用于伤口治疗。天然材料拥有良好的生物相容性和生物降解性，利用各种天然材料合成的水凝胶一直是研究的一大重点，但相对于使用合成材料制备的水凝胶，存在力学性能更差，形态难以保持的缺点，为其储存和使用增加了困难。目前，由天然材料或天然材料和合成材料联合制备的新型自愈水凝胶创面敷料由于具有抗破损的自愈能力，有望改良传统水凝胶的力学性能不足的缺陷。基于天然材料研发的伤口自愈水凝胶的研究现状做一综述，讨论了适合制备水凝胶的天然聚合物材料以及系统地阐述了自愈合的机理，然后介绍了自愈合水凝胶敷料的种类及讨论了自愈合水凝胶作为伤口敷料的应用。最后，讨论了天然材料制备的自愈水凝胶作为创面敷料的目前及未来的发展方向和使用途径，并对其的创新应用提出了建议。     

多肽水凝胶的研究进展

多肽水凝胶具有良好的生物相容性和可降解性,是一种很有前景的生物材料,按照交联方式的不同,多肽水凝胶可分为化学交联的水凝胶和物理水凝胶,本文中按此分类对多肽水凝胶的研究做了一个总结和简要评述,同时阐述了多肽水凝胶具有智能水凝胶的特点,并进一步对其在生物医学方面的应用进行了介绍和展望。     

双网络水凝胶的研究进展

双网络水凝胶在保持高吸水性等性能的基础上改善了传统水凝胶机械性能差、不稳定等缺点。重点介绍了双网络水凝胶及其在组织工程、伤口敷料、离子吸附、农林业等方面的应用。当在组织工程、导电和伤口敷料等医学领域应用时,水凝胶的生物相容性及力学性能成为研究重点;当应用在林业和吸附染料、离子方面时,水凝胶的溶胀性能较为重要。     

中科院纳米能源所李舟研究员课题组在导电水凝胶传感领域取得新进展

水凝胶是亲水性高分子分散在水相环境中形成的“保水”材料,通常情况下,其具有优异的生物相容性、力学柔韧性和环境友好等特点。通过多种物理化学方法,可以增强水凝胶的力学性能,如柔韧性和黏弹性能,进而实现水凝胶在可穿戴传感器方面的应用潜力。尽管目前有许多关于凝胶型力学传感器的报道,但是,一系列问题同时存在。如为了增强凝胶的可拉伸性能或者强度,科学家设计合成了各种复杂的高分子材料,通过在高分子链中引入特殊功能的化学基团,以增强水凝胶网络中的氢键、静电引力、金属螯合或者动态共价相互作用。     

蒽改性聚乙烯醇水凝胶的制备与表征

首先以蒽甲醛和聚乙烯醇(PVA)为原料、二甲基亚砜(DMSO)为溶剂、对甲苯磺酸(TsOH)为催化剂,反应得到蒽接枝改性聚乙烯醇(AnPVA)。然后利用混合溶剂凝胶法制备AnPVA水凝胶。通过差示扫描量热法(DSC)、拉伸等测试,研究水凝胶的力学等性能。结果表明,相比于纯PVA水凝胶,AnPVA水凝胶的力学性能得到了显著提高,在水凝胶中引入疏水基团是一种十分有效提高水凝胶力学性能的手段。AnPVA水凝胶浸泡于水中加热后无明显溶胀,有着优异的耐热和耐水性能,并且该水凝胶是物理交联网络,有着良好的循环重塑性能。     

高强度多孔聚乙烯醇水凝胶的制备

为制备兼顾多孔性和高强度的水凝胶,本研究利用循环冷冻和冷冻干燥联用设计和制备了一系列聚乙烯醇水凝胶。从聚乙烯醇溶液的浓度、循环冷冻次数、单次冷冻时长三个方面对水凝胶的力学性能、内部微观形貌、含水量进行了研究。结果表明:以质量分数14%浓度的聚乙烯醇水溶液经过3次循环冷冻过程(16h冷冻,8h解冻)和液氮冷冻冰干后的支架,再经溶胀平衡后得到的PVA水凝胶具有最佳的力学性能,此时PVA水凝胶的拉伸强度为5.74MPa,断裂伸长率为347%;改变循环冷冻次数可有效地调节PVA水凝胶的含水量;水凝胶力学性能提高来源于体系结晶度的增大。     

抗菌水凝胶在生物医学领域的研究进展

细菌感染是阻碍伤口愈合的重要因素之一,同时也是生物医学领域面临的一个重要问题。目前的抗菌水凝胶有着高抗菌活性、生物相容性以及可注射性等性能,并且其物理化学性质与生物组织相似,使得越来越多新型的抗菌水凝胶材料被用于治疗细菌感染。综述了近几年抗菌水凝胶的研究进展,归纳总结了几种不同类型的抗菌水凝胶的制备方法,抗菌活性和生物相容性等。重点阐述了抗菌水凝胶在伤口敷料、药物负载和传递以及组织工程等生物医学领域中的应用前景。     

Hybrid double‐network hydrogel based on poly(aspartic acid) and poly(acryl amide) with improved mechanical properties

Hydrogels usually have a smaller mechanical strength and toughness than generic polymeric materials. Therefore, many studies report improvements for mechanical properties of hydrogels by preparing double‐network hydrogels, nanocomposite hydrogels, and nanostructured hydrogels. In this study, interpenetrating‐type dually‐crosslinked hydrogels were prepared via free radical crosslinking polymerization of acrylamide monomers in the presence of poly(aspartic acid) and subsequent immersion in a metal ion containing aqueous solution to induce extra physical crosslinking through ionic or coordination bonding. Using this approach, the mechanical properties of inherently weak and brittle homopolymer gels could be improved via interpenetrating the double network formed by both covalent bonding and metal coordination‐assisted reversible physical crosslinks. The preparation, swelling behavior, morphology, and mechanical properties of these hydrogels are presented. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45925.     

High strength and bioactivity polyvinyl alcohol/collagen composite hydrogel with tannic acid as cross-linker

Hydrogels have great potential applications in biomedical materials, but their applications in complex physiological environments are severely limited by their weak strength and biotoxicity. Generally, synthetic polymer hydrogels and natural polymer hydrogels have complementary advantages in terms of mechanical strength and biological activity. Herein, tannic acid (TA), a natural material, was introduced into the polyvinyl alcohol/collagen (PVA-COL) double network to prepare a hydrogel (PVA-COL-TA) with good bioactivity and mechanical properties. The tensile strength of the composite hydrogel can reach up to 20 times that of the pure PVA hydrogel. And the hydrogel after swelling under physiological conditions also exhibits stable mechanical properties. The introduction of TA can reduce the degradation rate of COL, enabling it to continue to exert biological activity. in vitro cytocompatibility experiments showed that PVA-COL-TA hydrogel has good sustained biological activity and the potential for biomedical materials.     

Synthesis of dual physical self-healing starch-based hydrogels for repairing tissue defects

Hydrogels have the potential to simulate and permeate body tissues. They can be used in many biomedical applications, such as drug delivery, wound dressings, contact lenses, synthetic implants, biosensors, and tissue engineering. Despite recent significant advances in hydrogel fabrication, with the introduction of double network hydrogels, with ionic or hydrogen bonds, there is still the challenge of achieving optimal mechanical properties with appropriate self-healing ability. To solve the above problem, in this study, a new type of starch/chitosan/PVA/borax hydrogel was synthesized by adopting the one-pot method. The effect of concentration and ratio of raw materials on the final properties of hydrogels, such as the degree of hydrophilicity, morphology, degradation, mechanical strength, and drug release rate, was investigated. The properties of hydrogels were examined by scanning electron microscopy, thermogravimetric analysis, Fourier-transform infrared spectroscopy, X-ray diffractometry, and contact angle, which confirmed the composite synthesis and uniform distribution of HNT and curcumin. In addition, the composite hydrogel showed excellent mechanical properties. Drug release studies confirmed that the drug is slowly released from the nanocomposite hydrogels. The results showed that starch-based nanocomposite hydrogels could provide appropriate repairing potential for defects exposed to changeable parameters.     

Synthesis of poly(acrylic acid)–Fe3+/gelatin/poly(vinyl alcohol) triple‐network supramolecular hydrogels with high toughness,high strength and self‐healing properties

Hydrogels with good mechanical and self‐healing properties are of great importance for various applications. Poly(acrylic acid)–Fe³⁺/gelatin/poly(vinyl alcohol) (PAA‐Fe³⁺/Gelatin/PVA) triple‐network supramolecular hydrogels were synthesized by a simple one‐pot method of copolymerization, cooling and freezing/thawing. The PAA‐Fe³⁺/Gelatin/PVA triple‐network hydrogels exhibit superior toughness, strength and recovery capacity compared to single‐ and double‐network hydrogels. The mechanical properties of the synthesized hydrogels could be tailored by adjusting the compositions. The PAA‐Fe³⁺/Gelatin/PVA triple‐network hydrogel with 0.20 mmol Fe³⁺, 3% gelatin and 15% PVA could achieve good mechanical properties, the tensile strength and elongation at break being 239.6 kPa and 12.8 mm mm^?1, respectively, and the compression strength reaching 16.7 MPa under a deformation of about 91.5%. The synthesized PAA‐Fe³⁺/Gelatin/PVA triple‐network hydrogels have good self‐healing properties owing to metal coordination between Fe³⁺ and carboxylic groups, hydrogen bonding between the gelatin chains and hydrogen bonding between the PVA chains. Healed PAA‐Fe³⁺(0.20)/Gelatin3%/PVA15% triple‐network hydrogels sustain a tensile strength of up to 231.4 kPa, which is around 96.6% of the tensile strength of the original samples. Therefore, the synthesized triple‐network supramolecular hydrogels would provide a new strategy for gel research and expand the potential for their application. © 2019 Society of Chemical Industry     

Mechanical reinforcement of hydrogels by nanofiber network undergoing biaxial deformation

Hydrogels can encapsulate large quantities of water within a three‐dimensional crosslinked polymer network. Polyvinyl alcohol (PVA) hydrogels have been widely used in tissue engineering, wound dressing, and drug delivery. However, the inferior mechanical properties of PVA hydrogels limit their utility in load‐bearing applications. To alleviate this deficiency, we used a hybrid electrospinning/solution casting continuous process to reinforce PVA hydrogels using polyurethane nanofibers. In this process, the nanofibers were electrospun into the wet solution cast film prior to solidification. The reinforcement of PVA hydrogels at a series of extent of water swelling was determined using a custom built bubble biaxial stretching device. The results showed that nanofibers have substantial enhancement effect on mechanical properties particularly in thin hydrogel films at high water concentrations. Reduction of nanofiber diameter was also found to increase this reinforcement due to increased interfacial area between nanofibers and hydrogels. POLYM. COMPOS., 37:709–717, 2016. © 2014 Society of Plastics Engineers     

Supramolecularly Mediated Robust,Anti‐Fatigue,and Strain‐Sensitive Macromolecular Microsphere Composite Hydrogels

Hydrogels are increasingly investigated and applied in flexible electronic devices, but their practical applications are often restricted by the poor mechanical and limited anti‐fatigue properties. This works reports an approach to robust, anti‐fatigue, and strain‐sensitive hydrogels by introducing macromolecular microsphere and mediating their supramolecular cross‐linking points. A model network composed of sulfonated polystyrene (SPS) microspheres and poly(acrylamide‐co‐acrylic acid)/Fe³⁺ (poly(Am‐co‐AA)/Fe³⁺) is investigated. The resulting composite hydrogels have high tensile strength (4.29 MPa) and anti‐fatigue property. More interestingly, such composite hydrogels have strain‐dependent conductivity and can be applied in robust flexible strain sensors for monitoring various human motions. Overall, the hydrogels developed herein not only help to understand the enhancing mechanism of composite hydrogels, but also offer alternative materials for fabricating robust electronic devices.     

Preparation of hydrophilic polymer networks by post-curing reaction

Hydrophilic gels are a very important class of polymeric materials with extensive applications as biomedical products. The critical properties of hydrogels, such as sorption and desorption, mechanical behavior, swelling properties, etc., are controlled by network characteristics, i.e. degree of crosslinking and the density, distribution and length of crosslinks. Hydrogels prepared by copolymerization of 2-hydroxyethyl methacrylate (HEMA) with ethylene glycol dimethacrylate (EGDMA) have already been studied in detail. In this work, hydrophilic networks were prepared by crosslinking HEMA with EGDMA, and poly(2-hydroxy-ethyl methacrylate) (PHEMA) with diphenylmethane-4,4′-diisocyanate (MDI). The swelling properties of both types of networks were studied and the differences in behavior were attributed to the different techniques applied for network formation.     

Synthesis and characterization of photopolymerizable hydrogels based on poly (ethylene glycol) for biomedical applications

Hydrogels are polymeric materials widely used in medicine due to their similarity with the biological components of the body. Hydrogels are biocompatible materials that have the potential to promote cell proliferation and tissue support because of their hydrophilic nature, porous structure, and elastic mechanical properties. In this work, we demonstrate the microwave-assisted synthesis of three molecular weight varieties of poly(ethylene glycol) dimethacrylate (PEGDMA) with different mechanical and thermal properties and the rapid photo of them using 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184) as UV photoinitiator. The effects of the poly(ethylene glycol) molecular weight and degree of acrylation on swelling, mechanical, and rheological properties of hydrogels were investigated. The biodegradability of the PEGDMA hydrogels, as well as the ability to grow and proliferate cells, was examined for its viability as a scaffold in tissue engineering. Altogether, the biomaterial hydrogel properties open the way for applications in the field of regenerative medicine for functional scaffolds and tissues.     

Synthesis,characterization, and cytotoxicity of PCL–PEG–PCL diacrylate and agarose interpenetrating network hydrogels for cartilage tissue engineering

Hydrogels are suitable biomaterials for cartilage tissue engineering due to the excellent ability to retain water to provide suitable environment for the tissue, however, the insufficient mechanical properties often prevent their wider applications. The objective of this study was to fabricate biocompatible hydrogels with good mechanical performance, high-water content, and porous microstructure for cartilage regeneration. Photocrosslinked hydrogels are one of the most widely used systems in tissue engineering due to the superior mechanical properties. In this study, block copolymer, poly(ε -caprolactone)-poly(ethylene)-poly(ε -caprolactone) diacrylate (PCL–PEG–PCL; PEC), was prepared by ring-opening polymerization, and PEC hydrogels were made through free radical crosslinking mechanism. Agarose network is chosen as another component of the hydrogels, because of the high-swelling behavior and cartilage-like microstructure, which is helpful for chondrocytes growth. Interpenetrating networks (IPN) were fabricated by diffusing PEC into agarose network followed by photo-crosslinking process. It was noted that incorporating PEC into the agarose network increased the elastic modulus and the compressive failure properties of individual component networks. In addition, high-swelling ratio and uniform porosity microstructures were found in the IPN hydrogels. IPN and PEC showed low cytotoxicity and good biocompatibility in elution test method. The results suggest promising characteristics of IPN hydrogels as a potential biomaterial for cartilage tissue engineering.     

Ethanol organosolv lignin as a reactive filler for acrylamide‐based hydrogels

Hydrogels based on acrylamide (AM) and ethanol organosolv lignin (EOL) with high swelling and good mechanically elastic properties were synthesized in an alkaline solution. EOL was used as a reactive filler for the preparation of AM‐based hydrogels. The impact of EOL addition on the physicochemical properties of AM‐based hydrogels was investigated using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy, and their mechanical properties were examined. The water swelling ratio of the prepared hydrogels increased with the increase of EOL content, and their maximum swelling ratio could reach up to 180. Mechanical measurements indicated that their tensile strength was highly dependent on the amount of EOL, and their elongation at break reached up to 1400%. The formation mechanism of EOL composite hydrogels was probably that most of AM was synthesized into the crosslinked poly(acrylic amide) network, and small quantities of AM was hydrolyzed to acrylic acid ions under alkaline condition. The chain transfer of free radicals from AM and/or AA to EOL molecules occurred in the polymerization process. With increasing EOL content in the hydrogels, an interpenetrating polymer network might be mainly formed by the hydrogen bonding between EOL and AA and/or AM molecules. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42638.