芳叔胺体系引发乙烯类单体聚合的机理——自旋捕集ESR法

Study on the Polymerization Mechanism of Vinyl Monomers with the Initiation Systems of Aromatic Tertiary Amines——Spin Trapping Technique-ESR Method

采用自旋捕集ESR技术和紫外光谱法,研究了N,N-二甲基苯胺(DMA)-苄基氯(BC)引发甲基丙烯酸甲酯(MMA)自由基聚合的机理;DMA对MMA、丙烯酸甲酯(MA)、苯乙烯(St)及α-甲基苯乙烯(α-MeSt)烯类单体的引发作用。在60℃、无氧条件下、DMA-BC-MMA体系中可产生自由基其中仅有R3参与引发反应,由此证实了以前所提出的引发机理。DMA单独存在下与MMA、α-MeSt这些带有α-甲基的乙烯类单体也可形成活泼的自由基R3,并引发聚合;若与不带有α-甲基的乙烯类单体,如MA、St,则不能形成自由基R3,因此它们不能被引发聚合。

Two aspects were investigated with the spin trapping technique-ESR and UV: 1. The mechanism of radical chain polymerization of MMA, initiated by N,N-dimethylani line(DMA)-benzyl chloride(BC); 2. The initiation effect of DMA on vinyl monomers as MMA, MA, St and a-MeSt. The experimental results show that the radicals R2, R3 (R2: are generated in the system of DMA-BC-MMA without oxygen at 60℃. Then the initiation mechanism was proposed that only radical R3 could play the role of initiating species in the process of initiation. The radical R3 is also generated when DMA alone was used as initiator in the polymerization of such monomers as MMA, a-MeSt containing-methyl group, but it could not be generated when it combined with such monomers which do not possess a-methyl group as MA, St, and the polymerization could not take place.