Thermal stability of RAFT-based poly(methyl methacrylate): A kinetic study of the dithiobenzoate and trithiocarbonate end-group effect
Thermal stability of RAFT-based poly(methyl methacrylate): A kinetic study of the dithiobenzoate and trithiocarbonate end-group effect
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DOI：
10.1016/j.polymdegradstab.2019.03.017
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发表时间：
2019-06-01
影响因子：
5.9
通讯作者：
Kudryavtsev, Yaroslav V.
中科院分区：
文献类型：
--
作者：
Bekanova, Marianna Z.;Neumolotov, Nikolay K.;Kudryavtsev, Yaroslav V.
在100-180℃的动态加热和长时间等温处理下，系统地研究了可逆加成-破碎链转移（RAFT）聚合合成的二硫代苯甲酸酯（DB）和三硫代碳化酯（TC）端部聚甲基丙烯酸甲酯（PMMA）的热稳定性。结果表明，在功能端基的存在下，相对于传统的PMMA，质量损失的开始可以转移。温度升高（PMMA-DB）或降低（PMMA-TC）。无论聚合物的摩尔质量如何，PMMA链端功能的丧失在DB端基在120摄氏度恒温处理24小时后明显表现出来，而TC端基在100摄氏度恒温处理24小时后就已经表现出来了。在120℃（对于PMMA-TC）和140℃（对于PMMA-DB）时，这两种聚合物在链延伸过程中作为大分子RAFT试剂的能力几乎完全停止。官能团端基消除的动力学取决于它们的化学性质。在db -基团的情况下，反应是一级的，而含有两个C-S键的tc -基团表现出更复杂的降解动力学。我们提出了一种两步法消除tc基团的机制，该机制能够解释观察到的实验数据。(C) 2019 Elsevier Ltd.版权所有。
Thermal stability of dithiobenzoate- (DB) and trithiocarbonate- (TC) terminated poly(methyl methacrylate) (PMMA) synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization is systematically studied under dynamic heating and prolonged isothermal treatment at 100-180 degrees C. It is demonstrated that in the presence of functional end-groups the onset of mass loss can be shifted relative to conventional PMMA, either toward higher (PMMA-DB) or lower (PMMA-TC) temperatures. Irrespective of the polymer molar mass, a loss of PMMA chain-end functionality clearly manifests itself upon 24 h of isothermal treatment at 120 degrees C for DB end-groups and already at 100 degrees C for TC ones. At 120 degrees C (for PMMA-TC) and 140 degrees C (for PMMA-DB) the ability of both polymers to serve as macromolecular RAFT agents in the chain extension processes ceases almost completely. The kinetics of functional end-groups elimination depends on their chemical nature. In the case of DB-groups, the reaction is of the first order, whereas TC-groups containing two C-S bonds demonstrate more complex degradation kinetics. We propose a two-step mechanism of TC-group elimination, which enables interpretation of the observed experimental data. (C) 2019 Elsevier Ltd. All rights reserved.