【摘要】 设计合成了一类含苯硼酸和氨基结构的聚环氧乙烷(PEO)大分子交联剂,利用其与含聚乙烯醇(PVA)的三嵌段共聚物PVA-b-PEO-b-PVA之间的动态共价作用,构筑得到一类在生理pH下稳定,且对葡萄糖有响应的动态共价凝胶;详细研究了交联剂用量、PVA链段长度对凝胶化过程及凝胶稳定性的影响,证明PVA链段越长、交联剂用量越高,凝胶的稳定性越高,同时这类凝胶的屈服力较高,性质上更接近固体.凝胶在pH=7.4,37℃保持其结构稳定性.进一步发现这类动态共价凝胶具有较强的结构修复能力以及对糖的响应能力,凝胶可包载蛋白质FITC-BSA,加入葡萄糖后,其释放显著加快.更多还原

【Abstract】 Boronic acid can form dynamic covalent boronic ester bonds with 1,2-diol or 1,3-diol moieties. This property has been used to prepare malleable and self-healing covalent polymer networks as well as glucoseresponsive hydrogels. It remains a challenge to fabricate strong hydrogels with fast glucose-responsivity. Glucoseresponsive dynamic covalent hydrogels were prepared by crosslinking poly(vinyl alcohol)(PVA) containing triblock copolymer and poly(ethylene oxide)(PEO) containing phenylboric acid. Specifically, we synthesized a new type of α,ω-phenylboronic acid substituted PEO crosslinker. The feature of the crosslinker is that aminogroups are introduced to the neighboring position of boronic acid, which will accelerate the boronic ester exchange. The gelation of this crosslinker with three PVA-b-PEO-b-PVA triblock copolymers at physiological pH was examined. Time-dependent dynamic storage and loss modulus of the hydrogels were monitored by rheological measurements. Formation of hydrogels turned out be very fast after mixing the crosslinker and triblock copolymer solutions. Stable dynamic covalent hydrogels were obtained after incubating the hydrogels for 12 h.The copolymer composition, PVA chain length, and content of crosslinker were found to greatly affect the hydrogel properties. Higher polymer concentration, longer PVA chains, and more PEO crosslinker endowed hydrogels with higher modulus. Gels with high yield stress were obtained by utilizing block copolymer with longer PVA segments or adding more crosslinker. Both pH and temperature affected the hydrogel properties. The formed hydrogels displayed higher modulus at pH = 7.4 than those at pH = 6.0, and the stability of the hydrogel could still be maintained at 37℃. In addition, the hydrogels exhibited good structural recovery ability due to the covalent dynamic crosslinking. Finally, the hydrogels could load FITC-BSA, and the release profile of FITC-BSA was accelerated in the presence of glucose.更多还原