Main-chain degradable star polymers comprised of pH-responsive hyperbranched cores and thermoresponsive polyethylene glycol-based coronas†,Polymer Chemistry

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Main-chain degradable star polymers comprised of pH-responsive hyperbranched cores and thermoresponsive polyethylene glycol-based coronas†
Polymer Chemistry ( IF 4.1 ) Pub Date : 2018-09-13 00:00:00 , DOI: 10.1039/c8py01113c
Ulrike Wais _{1,

2,

3,

4,

5} , Lohitha Rao Chennamaneni _{1,

2,

3} , Praveen Thoniyot _{1,

2,

3} , Haifei Zhang _{4,

5,

6,

7} , Alexander W. Jackson _{1,

2,

3}

Affiliation

Core–shell polymeric architectures possessing stimuliresponsive behavior have great potential in triggered release systems, especially biomedical applications. Simultaneously achieving stimuliresponsive behavior and main-chain degradability is an interesting challenge facing modern polymer scientists. We report, the synthesis of star hyperbranched polymers possessing covalently cross-linked pH-responsive cores and linear thermoresponsive PEG-based coronas. Main-chain degradability throughout these structures is achieved via radical ring-opening polymerization of the cyclic ketene acetal 2-methylene-1,3-dioxepane, in combination with reversible-deactivation radical polymerization (RDRP) of methacrylate-based monomers. A two-step reversible addition–fragmentation chain-transfer (RAFT) polymerization is employed, initially facilitating the copolymerization of 2-(diethylamino)ethyl methacrylate and the divinyl cross-linker di(ethylene glycol) dimethacrylate to prepare pH-responsive hyperbranched polymers. Subsequent chain-extension with oligoethylene glycol methacrylate introduces a linear corona. Their ability to uptake and release hydrophobic actives in response to changes in pH is compared to a linear diblock copolymer micellar analogue. The star hyperbranched polymers have been modified post-polymerization by aminolysis to introduce reactive thiol sites, followed by thiol–maleimide click chemistry providing additional peripheral functionality. Hydrogels have also be prepared via disulfide bond formation between multiple star hyperbranched polymers. Finally, the synthetic methodology presented is further improved incorporating main-chain polyesters into both the hyperbranched core and linear corona. We describe the experimental conditions required to successfully prepare diblock and star hyperbranched polymers incorporating 2-methylene-1,3-dioxepane within each block via RAFT polymerization. The schizophrenic pH- and thermoresponsive self-assembly of these materials is investigated and their hydrolytic degradation presented.

中文翻译：

主链可降解星形聚合物由pH响应性超支化核和热响应性聚乙二醇基电晕组成†

具有触发响应行为的核-壳聚合物结构在触发释放系统（尤其是生物医学应用）中具有巨大潜力。同时实现刺激反应行为和主链可降解性是现代聚合物科学家面临的一个有趣的挑战。我们报告，具有共价交联的pH响应核心和线性热响应PEG基电晕的星形超支化聚合物的合成。这些结构中的主链可降解性是通过以下方式实现的环状乙烯酮缩醛2-亚甲基-1,3-二氧戊环的自由基开环聚合，以及甲基丙烯酸酯类单体的可逆失活自由基聚合（RDRP）。采用两步可逆的加成-断裂链转移（RAFT）聚合反应，首先促进了甲基丙烯酸2-（二乙氨基）乙酯与二乙烯基交联剂二乙二醇二甲基丙烯酸酯的共聚反应，从而制备了对pH敏感的超支化聚合物。随后用低聚甲基丙烯酸乙二醇酯进行链延长，引入线性电晕。与线性二嵌段共聚物胶束类似物相比，它们响应于pH的变化吸收和释放疏水活性物质的能力。星形超支化聚合物已通过氨解反应在聚合后进行了改性，以引入反应性硫醇位点，其次是硫醇-马来酰亚胺点击化学，提供了更多的外围功能。还可以制备水凝胶通过在多个星形超支化聚合物之间形成二硫键。最后，对提出的合成方法进行了进一步改进，将主链聚酯掺入超支化核和线性电晕中。我们描述了通过RAFT聚合成功制备每个嵌段内结合有2-亚甲基-1,3-二氧杂环丁烷的二嵌段和星形超支化聚合物所需的实验条件。研究了这些材料的精神分裂性pH值和热响应性自组装，并提出了它们的水解降解作用。

更新日期：2018-09-13

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