刺激响应降解型聚合物水凝胶

作为一类重要的高分子材料,聚合物水凝胶由于其优良的理化性能和生物学特性而被广泛应用于生物医药领域,降解特性是其作为生物医用材料的重要性能指标。刺激响应降解型水凝胶是指在环境因素刺激下凝胶网络发生响应性断裂,进而产生凝胶-溶胶或溶胀-降解转变的一类智能高分子材料。这一响应降解特性可通过将环境敏感性断裂基团引入到聚合物凝胶网络中来实现。与水凝胶常规的水解、酶解相比,刺激响应降解因具有空间或时间上的可控特性而引起人们的广泛关注。本文重点介绍了pH响应、光响应以及氧化还原响应降解型聚合物水凝胶的设计方法、降解机理及其最新研究进展,并对刺激响应降解型水凝胶未来的研究方向进行了展望。     

一种超支化聚硅烷的合成和性能

近年来,光电高分子的研究由于其在发光二极管、太阳能电池、光信息材料、传感器等方面的潜在应用而得到了广泛重视[1].自从英国剑桥大学Cavendish实验室的Burroughes等首次发现聚对亚苯基亚乙烯基的电致发光现象以来[2],共轭聚合物作为发光材料的研究迅速引起了人们的注意[3~5]     

新型pH及温度敏感性水凝胶

水凝胶是由三维交联网络结构的高聚物和介质共同组成的多元体系 ,因其独特的刺激响应行为 ,已在药物释放体系、物料分离、化学机械、人工肌肉等领域显示了良好的应用前景[1,2 ] .在人体体液这种复杂的环境中 ,水凝胶同时受到ｐＨ和温度等多重刺激作用 ,因此 ,研究多重响应性水凝胶具有重要意义 .聚氨酯作为一种广泛应用的高分子材料具有结构易调节、力学性能优异及生物相容性好等特点 ,在生物医学领域可将其用作假肢部件、外科用置入管、隐形眼睛等 .已有文献报道了ｐＨ敏感性聚氨酯水凝胶[3～ 5] ,但对多重响应性聚氨酯基水凝胶的报道还很…     

聚合物水凝胶体积相变过程中自发生成的新图案

聚合物水凝胶在 p H、温度等外界条件变化之下可发生连续或不连续的体积相变[1～ 6] .近年来 ,国际学术界认识到 ,凝胶的体积变化并不总是均匀地发生 ,伴随着剧烈的体积相变过程 ,凝胶中往往会呈现丰富多彩的图案[7～ 10 ] .这些图案已引起国际高分子学术界、包括研究材料力学行为和水母等“透明状动物”的科学家的极大兴趣 [11] .已发现了凝胶膨胀过程中的准六方凸起 [7]、凝胶急剧收缩过程中的竹节状条纹等图案 [8] .本文首次报道了凝胶的螺旋状图案 .Fig.1　 Typical Bamboo-like patterns formed in hydrogelshrinking after immersed…     

磺化聚苯乙烯胶体晶的红外光谱分析

单分散乳胶体系可以通过自组装形成有序的胶体晶结构 ,在窄波段光过滤器[1] 、生物医学传感器[2 ] 、智能化学传感器[3] 等领域具有重要的应用价值 .最近 ,人们以此有序结构作为模板 ,制备了有序孔材料[4～ 7] .另外 ,此有序结构在仿生学如模拟蛋白石等有序结构等方面也具有重要意义[8] .但是 ,一般的单分散体系如聚苯乙烯体系所形成的有序结构都属于硬性材料 ,缺乏对外场的响应特性 .此外 ,微球表面没有功能性基团 ,很难与其它物质兼容 ,这使得其作为模板合成其它复合材料的潜力大大降低 .本实验室通过对聚合物胶体晶进行改性 ,使其成为功…     

酶促水凝胶的合成及生物传感应用研究进展

近年来,聚合物基水凝胶材料已经成为一种独特的修饰材料,为新型生物传感器的设计提供了新思路.酶具有特异性高、毒性低、催化效率高等良好特性,已被用于催化聚合各种新型水凝胶.本文综述了几种酶促水凝胶的合成方法及其在细胞代谢物、组织工程、伤口愈合和癌症监测等方面的潜在应用,并对基于酶促水凝胶反应的生物传感器的制备与应用进行了总结与展望.     

聚合物纳米粒子的制备及其新型物理水凝胶结构的AFM和SEM研究

凝胶材料是生物系统的重要组成物质,在生物模拟、仿生等方面具有重大意义.最近凝胶方面的研究日益受到关注^[1,2],高分子凝胶体系的研究也得到深入开展^[3,4].在智能水凝胶、凝胶特性基础研究和医用凝胶材料等领域已取得了较大进展.     

离子液凝胶的研究进展

离子液凝胶结合了离子液体的稳定、不挥发、良好导电性以及普通凝胶的环境响应性智能特点,因而不但可用于制作新型太阳能电池、锂电池、超级电容器、人工肌肉和电致变色装置,还可作为功能膜材料用于催化反应和气体分离,以及作为生物传感器用于检测葡萄糖、多巴胺等生物分子.本文综述了近年来离子液凝胶主要的制备方法及其在电化学、热学、环境响应等方面的性能,展望了这些材料作为光电材料、功能膜材料和生物传感器的潜在巨大前景.     

一种新型的可生物降解的热敏凝胶微粒的制备

聚合物水凝胶是由高分子组成的三维空间交联网络与水的混合体系,有望在药物控制释放等领域获得广泛应用,某些水凝胶还具有显著的环境响应性,构成了一类主流的智能材料,在生物医用材料领域,对于材料的可降解性有严格要求,而单一的可降解药物缓释载体材料和单一的智能型水凝胶材料已有较多报道,但能够将这两种特性结合在同一种材料中的报道则很少,其中智能响应范围合适、降解速率易于大范围调节的合成水凝胶则更少。     

聚双(2-吡咯基乙氧基磷腈)的合成、氧化交联和导电性研究

有机 /无机杂化聚磷腈具有优良的加工性能和使用性能 ,可以在许多领域获得应用 [1] .具有光电活性的聚磷腈研究也引起了广泛的关注 [2～ 4 ] . Allcock等 [2 ] 合成了具有离子传导特性的聚磷腈 ,可应用于锂离子电池 .具有非线性光学特性的聚合物也有研究报道 [3 ] . L eung等 [4 ] 合成了具有电致发光基团的聚磷腈 ,部分聚合物具有蓝光发射的特征 .合成化学键合的聚 (N -烷基 )吡咯通用聚合物复合膜材料已经得到了重视[5,6] .本文合成了 2 -吡咯基乙醇 ,将其与反应性无机聚合物聚 (二氯 )磷腈进行高分子取代反应 ,合成了含吡咯侧基的聚磷…     

Thermoresponsive Macroporous Scaffolds Prepared by Emulsion Templating

A versatile method to prepare non‐covalently crosslinked polyHIPEs hydrogels from oil‐in‐water high internal phase emulsions (HIPEs) whose aqueous phase contained thermo‐responsive linear polymers is described. The interconnected pore structure of the polyHIPEs is maintained by reversible physical aggregation of thermo‐responsive polymer chains in an aqueous environment. This method to prepare interconnected porous hydrogels using a thermal trigger in the guise of thermo‐responsive polymers by emulsion templating requires no chemical reaction during solidification of the template. This particular feature could provide a safer route to injectable scaffolds as issues of polymerisation/crosslinking chemistry and residual initiator fragments or monomers do not arise     

Preparation and characterization of microwave-treated carboxymethyl chitin and carboxymethyl chitosan films for potential use in wound care application

CM-chitin and CM-chitosan films were successfully crosslinked by microwave treatment. Crosslinking of the microwave-treated CM-chitin films involved mainly the carboxylate and the secondary alcohol groups, while crosslinking of microwave-treated CM-chitosan films involved the carboxylate and the amino groups. In addition, the crystallinity of CM-chitin increased with increasing microwave treatment time, whereas an increase in the crystallinity of the microwave-treated CM-chitosan films was not observed. At a similar percentage of weight loss, the crosslinking of either CM-chitin or CM-chitosan films by microwave treatment required much less stringent condition when compared with the crosslinking by autoclave treatment. Based on both direct and indirect cytotoxicity assays, the cytotoxicity of the microwave-treated CM-chitin films was negative, while that of the microwave-treated CM-chitosan films was positive. Human fibroblasts adhered on the surface of microwave-treated CM-chitosan films much better than on the surface of microwave-treated CM-chitin films.     

Preparation and properties of alkoxy(methyl)silsesquioxanes as coating agents

Polysilsesquioxanes were prepared through the acid‐catalyzed hydrolytic polycondensation of triethoxy(methyl)silane, triisopropoxy(methyl)silane, or triisobutoxy(methyl)silane and subjected to dip coating to form coating films. The film formation depended on the polarity and crystallinity of the substrate, and a correlation was found between the substrate and polysilsesquioxane solubility parameters. When the coating film was heated, thermal condensation occurred at about 500 °C between hydroxy groups or between hydroxy and alkoxy groups. The methyl group attached to silicon decomposed, and siloxane bonding formed at about 800 °C. The adhesion and hardness of the coating films were evaluated with the Japanese Industrial Standard K5400 protocol, and they increased with increases in the heating time and heat‐treatment temperature. The refractive index of the coating films decreased when the heat‐treatment temperature was increased to 500 °C because of the combustion of organic groups. In contrast, the surface electric resistance increased with the heat‐treatment temperature up to 500 °C. The dielectric constant was 2.6–2.8 and decreased with an increases in the molecular weight and the degree of crosslinking of the polysilsesquioxanes. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3676–3684, 2004     

Superabsorbant hydrogels based on xanthan and poly(vinyl alcohol): 1. The study of the swelling properties

The swelling properties of some superabsorbant composite hydrogels, based on xanthan and poly(vinyl alcohol) and crosslinked with epichlorohydrin, were studied. The maximum swelling degree of the hydrogels and the swelling rate constant were determined as a function of the hydrogel's composition (the % of poly(vinyl alcohol) in the polymer mixture and the amount of crosslinking agent), the crosslinking reaction conditions (the time and the temperature of the crosslinking reaction), and the composition of the swelling solutions (the glycerin/water ratio and the concentration of the electrolyte).     

磁性半互穿网络智能水凝胶的合成及性质评价

以甲基丙烯酸(MAA)、N-异丙基丙烯酰胺(NIPAAm)、丙烯酰胺(AM)为原料,N,N′-亚甲基双丙烯酰胺(MBA)为交联剂,利用IPN技术并结合磁性的γ-Fe2O3增强剂,在水溶液中制备了半互穿网络水凝胶(PMAA/PAM-NIPAAm/γ-Fe2O3),研究了水凝胶的溶胀性﹑热稳定性和电磁性。实验表明,水凝胶形成稳定的IPN互穿网络结构且该水凝胶具温度、pH双重敏感性和顺电磁性。所合成的水凝胶在低临界溶解温度31℃以下,具有明显正向温敏性,高于此温度,水凝胶的温度敏感性会逐渐减弱。产品成功克服了NIPAAm类水凝胶的温缩性。     

Bentonite Reinforced Tough Composite Hydrogels as Potential Artificial Articular Cartilage

Novel tough composite hydrogels were prepared from inorganic bentonite(IB), polyvinyl alcohol(PVA) and polyethylene glycol(PEG) by means of a freeze-thaw technique, during which IB acted as multifunctional physically crosslinking junction and a filler to bridge the 3D network hydrogel; while the physical adsorption between IB and the polymer chains served as sacrificial bonds and increased the energy dissipation efficiency. The effects of different content of IB(w_IB) on the morphological, thermal, swelling, and mechanical properties of the hydrogels were investigated. It was found that the added IB promoted the material crosslinking and stability, and the mechanical properties of the hydrogels were significantly improved with increasing w_IB. The highest tensile stress of the hydrogel was achieved(1.1 MPa) when w_IBwas 5%. The synthesized hydrogels with high mechanical strength and low friction coefficient are potential candidate materials for artificial cartilage.     

Injectable Hyaluronic Acid/Poly(γ-glutamic acid) Hydrogel with Step-by-step Tunable Properties for Soft Tissue Engineering

Injectable hydrogels as an important class of biomaterials have gained much attention in tissue engineering. However, their crosslinking degree is difficult to be controlled after being injected into body. As we all know, the crosslinking degree strongly influences the physicochemical properties of hydrogels. Therefore, developing an injectable hydrogel with tunable crosslinking degree in vivo is important for tissue engineering. Herein, we present a dual crosslinking strategy to prepare injectable hydrogels with step-by-step tunable crosslinking degree using Schiff base reaction and photopolymerization. The developed hyaluronic acid/poly(γ-glutamic acid)(HA/γ-PGA) hydrogels exhibit step-bystep tunable swelling behavior, enzymatic degradation behavior and mechanical properties. Mechanical performance tests show that the storage moduli of HA/γ-PGA hydrogels are all less than 2000 Pa and the compressive moduli are in kilopascal, which have a good match with soft tissue. In addition, NIH 3 T3 cells encapsulated in HA/γ-PGA hydrogel exhibit a high cell viability, indicating a good cytocompatibility of HA/γ-PGA hydrogel.Therefore, the developed HA/γ-PGA hydrogel as an injectable biomaterial has a good potential in soft tissue engineering.     

Effects of annealing and the addition of PEG on the PVA based hydrogel by gamma ray

Poly(vinyl alcohol) (PVA) is an interesting material with good biocompatibility, high elasticity and hydrophilic characteristics. PVA hydrogels have been formed through chemical crosslinking with aldehyde, photopolymerization and physical crosslinking with freeze-thawing. In this study, crosslinked hydrogels based on PVA, and poly(ethylene glycol) (PEG) were prepared by gamma-ray irradiation, and then annealed at 120 °C. The properties of a hydrogel such as gel fraction, swelling behavior, gel strength as a function of PEG content and annealing time were investigated. Also, the thermal behaviors were examined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The gel fraction decreases with an increase in PEG content and decrease in annealing time. The tensile strength increases with an increase in annealing time. The thermal behaviors have shown different patterns according to the annealing time. The improved properties suggest that PVA/PEG blend hydrogel can be a good candidate for applications in the articular cartilage.     

Biodegradable and pH-sensitive hydrogels: Synthesis by crosslinking of N,N-dimethylacrylamide copolymer precursors

Novel pH-sensitive hydrogels containing azoaromatic crosslinks were synthesized by the crosslinking of polymeric precursors. First, a reactive polymeric precursor was synthesized by copolymerization of N,N-dimethylacrylamide, N-tert-butylacrylamide, acrylic acid, and N-methacryloylglycylglycine p-nitrophenyl ester. The hydrogel was prepared in the second step by the reaction of the polymeric precursor with N,N′-(ω-aminocaproyl)-4,4′-diaminoazobenzene. The hydrogels were characterized by the network structure, (that is, content of crosslinks, unreacted pendent groups, and cycles), the equilibrium swelling ratio as a function of pH, modulus of elasticity in compression, and the degradability in vitro. The results obtained indicated that the hydrogel network structure strongly depends on the reaction conditions such as polymer concentration, and the ratio of the reactive groups during the crosslinking reaction. The swelling and mechanical properties of hydrogels can be controlled by the modification of polymer backbone structure and/or the crosslinking density. The rates of hydrogel degradation depended on their degree of swelling. The higher the degree of swelling, the higher the degradability. The properties of the hydrogels suggest that they have a potential as carriers for colon-specific drug delivery. © 1994 John Wiley & Sons, Inc.     

Crosslinking Parameter on the Preparation of Cellulose Based Hydrogel with Divynilsulfone

Polymeric hydrogels are crosslinked polymers which display high sorption capacity in water and water solution. In this work, cellulose based hydrogel was prepared with divinylsulfone as crosslinking agent. Cellulose based hydrogel was synthesized as a mixture of sodium salt of carboxymethylcellulose (CMCNa) and hydroxyethylcellulose (HEC). The effect of chemical composition, temperature and reaction time during crosslinking processes was investigated both the value of equilibrium water uptake and swelling ratio. Infrared spectra of the synthesized polymeric networks were studied to investigate the chemical structure of crosslinking reaction qualitatively. The thermal properties and morphology of the obtained cellulose based hydrogels were observed by means of TGA (thermo-gravimetry analysis) and SEM (scanning electron microscopy), respectively. Crosslinking of CMCNa/HEC polymeric network results in a decrease in thermal stability. Hydrogel with weight ratio of CMCNa/HEC 5 to 1 at reaction temperature of 60 °C gave the highest absorption capacity in distilled water.