HTEMPO和TMPD调控下MMA可控/活性光聚合研究

以HTEMPO(2,2,6,6-四甲基-4-羟基哌啶-1-氧自由基)和TMPD(2,2,6,6-四甲基哌啶酮)为调控介质, 以Irgacure 651为引发剂, 研究了甲基丙烯酸甲酯(MMA)光聚合体系的控制反应动力学, 比较了单分子(HTEMPO为调控介质)和双分子(HTEMPO和TMPD为调控介质)调控体系, 并讨论了HTEMPO和HTEMPO/TMPD在MMA光聚合体系中的调控作用、 光敏化作用和原位光氧化反应. 结果表明, 对MMA光聚合体系, 以HTEMPO/TMPD为控制介质的双分子调控体系是有效的, 获得了良好的ln(\M0\]/\M\])与时间, 数均分子量与转化率之间的线性动力学关系, 并且PMMA均聚物的多分散性指数(PDI)随着转化率的提高而减小. 在高转化率(>85%)下, 体系的多分散性指数(PDI)最小值可达到1.2.

Controlled/Living Photopolymerization of Methyl Methacrylate Mediated by Bimolecular Systems for HTEMPO/2,2,6,6-Tetramethyl-Piperidinone

Controlled/living photopolymerization of methyl methacrylate(MMA) mediated by bimolecular systems for 4-hydroxy-2,2,6,6-tetramethyl-piperidinyl-1-oxyl(HTEMPO) and 2,2,6,6-tetramethyl-piperidinone(TMPD) was performed at ambient temperature.The effects of HTEMPO,TMPD and their different molar ratio as a mediator and photo-induced oxidization in situ of TMPD in the system were discussed respectively.It is shown that the molecular weight(M_n) of MMA homopolymer increased linearly and the polydispersity index(PDI) decreases with the conversion increasing,even until the conversion up to 80%,mediated by bimolecular system with both HTEMPO and TMPD,which is the characteristic of a controlled/living free radical polymerization.It is found that the obtained MMA homopolymer prepared by the photopolymerization exhibited a narrow molecular weight distribution as was characterized by GPC,the smallest value of PDI is 1.2.The result also shows that the bimolecular systems with HTEMPO/TMPD as a mediator has a better controlling kinetic performance than that only mediated by HTEMPO under the same condition.