Arm‐first star‐polymer synthesis in one‐pot via alkylborane‐initiated RAFT,Journal of Polymer Science

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Arm‐first star‐polymer synthesis in one‐pot via alkylborane‐initiated RAFT
Journal of Polymer Science ( IF 3.9 ) Pub Date : 2020-04-07 , DOI: 10.1002/pol.20200089
Renee L. Timmins ₁ , Olivia R. Wilson ₁ , Andrew J. D. Magenau ₁

Affiliation

An alkylborane initiated reversible addition‐fragmentation chain transfer (AI‐RAFT) process was developed for the synthesis of star‐polymers using a one‐pot approach at room‐temperature in the presence of oxygen. Linear poly(tert‐butyl acrylate) arms were first polymerized using a latent trialkylborane‐amine initiator, which generated trialkylborane, in situ, and subsequently radicals after reaction with oxygen. Polymerizations were optimized to maximize monomer conversion (~70–80%) and minimize arm‐dispersity (~1.10) through the oxygen concentration, initiator concentration, and polymerization time. The oxygen concentration was a critical AI‐RAFT parameter, providing maximum conversion at a ~0.5:1 molar ratio of oxygen‐to‐initiator. After arm‐polymerization, multifunctional acrylates were injected into the reactor to commence crosslinking without intermediate purification. The impact of the crosslinking time and the crosslinker's functionality, concentration, and injection time were investigated to enhance arm incorporation and diminish star‐polymer dispersity, quantified by deconvolution of size‐exclusion chromatography data. Crosslinker concentration had the largest influence on arm conversion with optimal concentrations at a 20‐25‐fold excess to chain transfer agent. Under optimal conditions, arm conversions were maximized to ~75–85% and star‐dispersity minimized to ~1.35–1.50. Herein an initial effort is made toward the synthesis of star‐polymers with well‐defined structures and high‐arm conversions, while also striving for oxygen tolerance, minimal purification, low‐temperatures, and metal‐free conditions.

中文翻译：

通过烷基硼烷引发的RAFT在一个锅中进行手臂优先的星形聚合物合成

开发了烷基硼烷引发的可逆加成-断裂链转移（AI-RAFT）工艺，用于在室温下在氧气存在下使用单锅法合成星形聚合物。首先使用潜在的三烷基硼烷-胺引发剂聚合线性聚（丙烯酸叔丁酯）臂，后者原位生成三烷基硼烷，然后与氧反应后产生自由基。通过氧气浓度，引发剂浓度和聚合时间，对聚合进行了优化，以最大程度地提高单体转化率（〜70–80％），并使臂分散度（〜1.10）最小化。氧气浓度是关键的AI-RAFT参数，在氧气与引发剂的摩尔比约为0.5：1时提供最大的转化率。手臂聚合后，将多官能丙烯酸酯注入反应器以开始交联，而无需中间纯化。通过尺寸排阻色谱数据的反卷积量化，研究了交联时间和交联剂功能，浓度和注入时间的影响，以增强臂的结合并减少星型聚合物的分散性。交联剂浓度对臂转化的影响最大，最佳浓度比链转移剂高20-25倍。在最佳条件下，臂转化率最大达到〜75–85％，而星散度最小化为〜1.35-1.50。在此，我们开始了合成具有明确结构和高臂转化率的星型聚合物的工作，同时还努力实现耐氧性，最低限度的纯化，低温和无金属的条件。

更新日期：2020-04-07

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