Switchable reversible addition–fragmentation chain-transfer (RAFT) agents, so-called because they can be reversibly switched by an acid/base stimulus to offer very good control over polymerization of both “more-activated” monomers (MAMs) and “less-activated” monomers (LAMs), provide a route to prepare well-defined polyMAM-block-polyLAM copolymers. This paper presents ¹H NMR studies in determining the effect of the type and amount of acid on the efficiency of the protonation of a switchable RAFT agent. Acid type and concentration have a marked effect on the degree of control over switchable RAFT polymerization. Best control was achieved with a stoichiometric amount of the strongest acid investigated, trifluoromethanesulfonic acid. In addition, we describe a facile synthesis of the well-defined CO₂-responsive gradient copolymers poly(benzyl methacrylate)-block-(poly(N,N-diethylaminoethyl methacrylate)-gradient-poly(N-vinylpyrrolidone))-block-poly(N-vinylpyrrolidone) (PBzMA-b-P(DEAEMA-grad-NVP)-b-PNVP) through switchable RAFT polymerization. The amphiphilic gradient copolymers can self-assemble to form various multicompartment micelles in selective solvents, and the assembled micelles widely possess patchy, noncontinuous subdomains around the inner micelle cores. Through CO₂ stimulation, their inhomogeneous nature will endow the gradient copolymers with some different stimuli-responsive factors from those of block copolymers, which emerged with obviously heterogeneous and compartmentalized shell nanodomains. Furthermore, this gradient strategy may offer a new way to design and realize precise morphological manipulation.

中文翻译：

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可转换的RAFT聚合合成CO2反应性梯度共聚物及其可控的自组装

可切换的可逆加成-断裂链转移（RAFT）试剂，之所以如此，是因为它们可以通过酸/碱刺激进行可逆切换，从而对“更多活化”的单体（MAM）和“较少活化的”单体的聚合提供很好的控制。活化的”单体（LAM），为制备定义明确的polyMAM-嵌段-polyLAM共聚物提供了一条途径。本文介绍¹1 H NMR研究确定酸的类型和量对可切换RAFT剂的质子化效率的影响。酸的类型和浓度对可切换RAFT聚合反应的控制程度有显着影响。化学计量的最强酸三氟甲磺酸可实现最佳控制。此外，我们描述了良好定义的CO的简便合成₂响应性梯度共聚物聚（甲基丙烯酸苄酯） -嵌段- （聚（Ñ，Ñ -diethylaminoethyl甲基丙烯酸酯） -梯度-聚（Ñ乙烯基吡咯烷酮）） -嵌段-聚（N-乙烯基吡咯烷酮）（PBzMA- b-P（DEAEMA- grad -NVP）-b -PNVP）通过可切换的RAFT聚合。两亲性梯度共聚物可以在选择性溶剂中自组装形成各种多室胶束，并且组装的胶束在内部胶束核心周围广泛地具有斑片状，不连续的子域。通过CO ₂刺激，它们的非均质性质将使梯度共聚物具有与嵌段共聚物不同的一些刺激响应因子，而嵌段共聚物则出现明显的异质和间隔壳纳米域。此外，这种梯度策略可能为设计和实现精确的形态学处理提供新的途径。