Abstract

A glucose-sensitive polymer, poly(N-isopropylacrylamide-co-2-acrylamidophenylboronic acid) (P(NIPAM-co-2-AAPBA)), was synthesized by reversible addition fragmentation chain transfer (RAFT) copolymerization. Addition of glucose results in reduced solubility and hence increased turbidity, rather than the normal increase in solubility (decreased turbidity) observed for other PBA-based glucose-sensitive polymers. The novel glucose-sensitive behavior is explained by a new mechanism, in which glucose acts as an additive and depresses the lower critical solution temperature (LCST) of the polymer, instead of increasing solubility by increasing the degree of ionization of the PBA groups. Experimental and theoretic analysis for the influence of glucose on the thermal behavior of P(NIPAM-co-2-AAPBA) reveals that glucose depresses the LCST of P(NIPAM-co-2- AAPBA) copolymers in a two-stage manner, a fast decrease at low glucose concentrations followed by a slow decrease at high glucose concentrations. For low glucose concentrations, the binding of glucose with PBA groups on the polymer chain increases the number of glucose molecules proximal to the polymer which influences the thermal behavior of the polymer, causing a rapid decrease in LCST. Importantly, the transition occurs at a glucose concentration equal to the reciprocal of the binding constant between PBA and glucose, thus providing a novel method to determine the binding constant. Other saccharides, including mannose, galactose and fructose, also depress the LCST of P(NIPAM-co-2-AAPBA) copolymer in the same way.

中文翻译：

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对P（NIPAM- co -2-AAPBA）的新型葡萄糖敏感性行为的机理研究

摘要

葡萄糖敏感聚合物，聚（Ñ -isopropylacrylamide-共-2- acrylamidophenylboronic酸）（P（NIPAM-共通过可逆加成断裂链转移（RAFT）共聚合成-2-（AAPBA）。葡萄糖的添加导致溶解度降低，因此浊度增加，而不是其他基于PBA的葡萄糖敏感性聚合物所观察到的溶解度正常增加（浊度降低）。这种新的葡萄糖敏感性行为是通过一种新的机理来解释的，其中葡萄糖充当添加剂并降低聚合物的较低临界溶液温度（LCST），而不是通过增加PBA基团的电离度来增加溶解度。实验和葡萄糖对P的热行为的影响理论分析（NIPAM-共-2- AAPBA）表明葡萄糖按下P的LCST（NIPAM-共（2-AAPBA）共聚物以两阶段的方式，在低葡萄糖浓度下快速降低，然后在高葡萄糖浓度下缓慢降低。对于低葡萄糖浓度，葡萄糖与聚合物链上PBA基团的结合增加了邻近聚合物的葡萄糖分子的数量，这影响了聚合物的热行为，导致LCST迅速降低。重要的是，在等于PBA和葡萄糖之间的结合常数的倒数的葡萄糖浓度下发生转变，因此提供了确定结合常数的新方法。其他糖类，包括甘露糖，半乳糖和果糖，也以相同的方式抑制P（NIPAM- co -2-AAPBA）共聚物的LCST 。