甲基丙烯酸正丁酯正相微乳液可控/“活性”光聚合动力学研究

以末端含溴原子的光引发剂2-溴异丁酰氧基-2-甲基-1-苯基甲酮(HMPP-Br)为引发剂,2,2,6,6-四甲基哌啶-1-氧自由基(TEMPO)和2,2,6,6-四甲基哌啶醇(TMP)为调控剂,采用光聚合方法研究了甲基丙烯酸正丁酯(n-BMA)/十二烷基硫酸钠(SDS)/水/正丁醇 O/W型正相微乳液体系的光聚合反应动力学.结果表明,改性后的引发剂具有一定的引发活性,且聚合微乳液体系较稳定,聚合反应获得了良好的lnM]₀/M]与时间、数均分子量与转化率之间的线性动力学关系,制备了分子量分布较窄的Poly(n-BMA)均聚物.

Control/Living Free Radical Photopolymerization of n-Butyl Methacrylate in O/W Microemulsion

Using 2-bromo-(2-methyl-1-oxopropoxy)-2-methyl-propio-phenone(HMPP-Br) as a photoinitiator,the controlled/living photopolymerization of n-butyl methacrylate(n-BMA) mediated by 2,2,6,6-tetramethyl-piperidinyl-l-oxyl(TEMPO) and 2,2,6,6-tetramethyl-4-piperidinol(TMP) in the microemulsion of n-BMA/n-butanol/SDS-H2O system(O/W) was performed at ambient temperature.The controlling mechanism and reaction kinetics of controlled/living free radical photopolymerization of n-BMA in microemulsion was investigated.It was shown that the monomer conversion increased linearly with the increased exposure time,and the number-average molecular weight(Mn) of Poly(n-BMA) is increased linearly with the monomer conversion increasing under the condition with/=1.1,the content of initiator of 4.5%(mass fraction) and the irradiation intensity of 5.5 mW/cm2.The results show that when it was mediated by TEMPO/TMP,the photopolymerization of n-BMA in the microemulsion was to be kineticly controlled.It was found that the plots of number-average molecular weight vs.conversion and ln(M]0/M]) vs.time were liner respectively,and the n-BMA homopolymers exhibited relatively narrow molecular weight distributions(PDI=1.25—1.45),even until the conversion was up.This shows that TEMPO combined with TMP used as a mediator was evidently available.