Facile conversion of RAFT polymers into hydroxyl functional polymers: a detailed investigation of variable monomer and RAFT agent combinations
Facile conversion of RAFT polymers into hydroxyl functional polymers: a detailed investigation of variable monomer and RAFT agent combinations
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DOI：
10.1039/b9py00273a
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发表时间：
2010-07-01
影响因子：
4.6
通讯作者：
Barner-Kowollik, Christopher
中科院分区：
文献类型：
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作者：
Dietrich, Mathias;Glassner, Mathias;Barner-Kowollik, Christopher
我们报告了最近引入的甲基丙烯酸酯和丙烯酸酯型聚合物通过可逆加成断裂链转移（RAFT）聚合成羟基官能聚合物的一锅法自由基转化的系统研究。简单的反应程序包括在环境空气存在下，在升高的温度（T = 60 ° C）下搅拌RAFT官能聚合物和偶氮引发剂在四氢呋喃中的溶液。随后将形成的氢过氧化物官能聚合物还原成羟基官能聚合物是使用三苯基膦在一锅法中实现的。本研究中研究的聚合物是聚（丙烯酸甲酯）（pMA），聚（丙烯酸丁酯）（pBA），聚（丙烯酸异冰片酯）（piBoA）和聚（丙烯酸叔丁酯）（ptBA），带有二硫代苯甲酸酯或苯基二硫代乙酸酯末端以及对称的三硫代碳酸酯中链功能。当使用三硫代碳酸酯官能聚合物时，观察到定量转化成过氧化氢和羟基封端的产物。在二硫代苯甲酸酯和苯基二硫代乙酸酯官能的丙烯酸类聚合物的情况下，由于RAFT端基的氧化而产生一些少量副产物。采用尺寸排阻色谱（SEC）和尺寸排阻色谱-电喷雾质谱（SEC-ESI-MS）监测反应进程并研究模型聚合物的反应机理。当在转化反应中使用三硫代碳酸酯官能聚合物时，SEC分析显示初始M-n的二等分。对中间反应产物进行碰撞诱导解离（CID）MS实验，以获得有关化学结构的深入信息。新的主链连接的羟基为化学端基转化和与RAFT制备的聚合物的缀合反应提供了通用的锚，缓解了二硫酯端基进行非自由基转化的能力相当有限的问题。
We report the systematic investigation of a recently introduced one-pot radical transformation of methacrylate and acrylate-type polymers prepared via reversible addition fragmentation chain transfer (RAFT) polymerization into hydroxyl functional polymers. The simple reaction procedure involves stirring a solution of the RAFT functional polymer and an azo-initiator in tetrahydrofuran at elevated temperatures (T = 60 degrees C) in the presence of ambient air. Subsequent reduction of the formed hydroperoxide functional polymers to hydroxyl functional polymers is achieved in a one-pot procedure using triphenylphosphine. Polymers investigated in the current study are poly(methyl acrylate) (pMA), poly(butyl acrylate) (pBA), poly(isobornyl acrylate) (piBoA) and poly(tert-butyl acrylate) (ptBA) carrying a dithiobenzoate or phenyldithioacetate end terminius as well as a symmetrical trithiocarbonate mid chain function. Quantitative conversion into the hydroperoxyl and hydroxyl terminated product is observed when trithiocarbonate functional polymers are employed. In the case of dithiobenzoate and phenyldithioacetate functional acrylic polymers, some minor side products due to the oxidation of the RAFT end-group are generated. Size exclusion chromatography (SEC) and size exclusion chromatography-electrospray mass spectrometry (SEC-ESI-MS) were employed to monitor the progress of the reaction and to investigate the proposed reaction mechanism for the model polymers. When trithiocarbonate functional polymers are employed in the transformation reaction, the SEC analysis shows a bisection of the initial M-n. Collision induced dissociation (CID) MS experiments of the intermediate reaction products were conducted to gain in-depth information about the chemical structure. The new backbone linked hydroxyl group provides a versatile anchor for chemical end-group conversions and conjugation reactions with RAFT prepared polymers, alleviating problems with the rather limited ability of the dithioester end-group to undergo non-radical transformations.