芳香叔胺引发丙烯腈光聚合的引发机理

芳香叔胺引发丙烯腈(AN)光聚合是通过形成激基复合物(exciPlex)进行的。紫外光谱和荧光光谱表明,芳香叔胺在基态可以和AN形成电荷转移复合物(CTC),而在激发态可和AN形成exciplc(称定域激发)。CTC经光照亦可激发(称CTC激发)。 定域激发引起光聚合速率为CH_3C_6H_4N(CH_3)_2>C_6H_5N(CH_3)_2>HOCH_2·C_6H_4N(CH_3)_2>CH_3C_6H_4N(CH_2CH_2OH)_2,与芳胺荧光被AN淬灭的Stern-Vo-lmer常数顺序一致。CTC激发引起的光聚合顺序为:CH_3C_6H_4N(CH_3)_2>CH_3C_6H_4N(CH_2CH_2OH)_2>HOCH_2C_6H_4N(CH_3)_2>C_6H_5N(CH_3)_2,与芳胺上取代基推电子能力一致。端基分析表明聚合物有芳胺端基。

THE INITIATION MECHANISM OF PHOTOPOLYMERIZATION OF ACRYLONITRILE WITH AROMATIC TERTIARY AMINES AS INITATORS

We have verified the formation of exciplex in the photopolymerization of AN initiated with aromatic tertiary amines. From UV spectra and fluorescence spectra we are inclined to believe that aromatic tertiary amine in the ground state will form charge-transfer complex (CTC) with AN which may be excited to exciplex by irradiation (CTC excitation), while in excited state it will also form exciplex with AN through local excitation.The order of photopolymerization rate of AN caused by local excitation is found to be CH3C6H4N(CH3)2 > C6H5N(CH3)2 > HOCH2C6H4N(CH3)2 > CH3C6H4N(CH2CH2OH)2 and this is in agreement with the order of stern-Volmer constant for the quenching of fluorescence of amines by AN. The order of photopolymerization rate caused by CTC excitation is found to be CH3C6H4N(CH3)2 > CH3C6H4N (CH2CH2OH)2 > HOCH2C6H4N ·(CH3)2 > C6H5N(CH3)2, which is in agreement with ability of donating electron of the substituted group on the benzene ring of aromatic amines.The presence of small amount of aromatic amine group as end-group in the polymer molecule has been detected by UV spectra.