Semidegradable nanoparticles were synthesized in aqueous medium by photoinitiated polymerization-induced self-assembly, using a cleavable hydrophilic copolymer as a steric stabilizer that also served as a macromolecular chain transfer agent (mCTA) for the reversible addition–fragmentation chain transfer (RAFT) polymerization of 2-hydroxypropyl methacrylate (HPMA). This mCTA was obtained by modification of a pH-sensitive poly[(ethylene carbonate)-co-(ethylene oxide)] (PECEO) random copolymer that was end-fitted with a trithiocarbonate moiety. By adjusting the degree of polymerization of HPMA through RAFT, we achieved the synthesis of a series of amphiphilic block copolymers that self-assembled in various morphologies, including spheres, worms, and vesicles. Through characterization by ¹H nuclear magnetic resonance, size exclusion chromatography, and transmission electron microscopy, it could be demonstrated that the carbonate linkages of their hydrophilic block and of their steric stabilizer undergo hydrolysis under alkaline conditions. The length of the PHPMA block and the balance between the hydrophilic and hydrophobic blocks are two parameters that have a significant impact on the self-assembly of these particles; a transition from steric to electrostatic stabilization of these nanoparticles could be witnessed during degradation for short PHPMA blocks. In summary, pH-sensitive nanoparticles sterically stabilized by degradable poly(ether-co-ether carbonate) copolymers gave rise under basic conditions to nanoparticles stabilized by electrostatic interaction.

中文翻译：

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通过光聚合诱导自组装获得的壳类可降解水性颗粒从空间稳定到静电稳定的转变


半可降解纳米颗粒是通过光引发聚合诱导的自组装在水性介质中合成的，使用可裂解的亲水性共聚物作为空间稳定剂，该共聚物还用作 2-羟丙基甲基丙烯酸酯 （HPMA） 的可逆加成-碎裂链转移 （RAFT） 聚合的大分子链转移剂 （mCTA）。该 mCTA 是通过对 pH 敏感的聚[（碳酸乙烯酯）-共-（环氧乙烷）] （PECEO） 无规共聚物进行改性而获得的，该聚物末端与硫代碳酸酯部分相配。通过RAFT调节HPMA的聚合度，我们实现了一系列两亲性嵌段共聚物的合成，这些共聚物以各种形态自组装，包括球体、蠕虫和囊泡。通过 ¹H 核磁共振、尺寸排阻色谱和透射电子显微镜表征，可以证明它们的亲水嵌段和空间稳定剂的碳酸盐键在碱性条件下发生水解。PHPMA 嵌段的长度以及亲水和疏水嵌段之间的平衡是对这些颗粒的自组装有重大影响的两个参数;在短 PHPMA 块的降解过程中，可以观察到这些纳米颗粒从空间稳定到静电稳定的转变。总之，由可降解的聚（醚-共醚-碳酸盐）共聚物空间稳定的 pH 敏感纳米颗粒在基本条件下产生了通过静电相互作用稳定的纳米颗粒。