芳香叔胺引发丙烯腈光聚合研究

我们发现芳香叔胺是丙烯腈聚合极有效的光引发剂。芳香叔胺苯环上氢被正性基取代时,引发能力增加,被负性基取代时,引发能力下降。下列胺的活性次序是:N,N-二甲基对甲苯胺(DMT)>N,N-二羟乙基对甲苯胺(DHET)>N,N-二甲基苯胺(DMA)>N,N-二甲胺基苯甲醛(DMB)>N,N-二甲基对硝基苯胺(DNA)。芳香叔胺引发丙烯腈光聚合属自由基机构,聚合速度与叔胺浓度的0.66次方成正比。在叔胺浓度为10~(-2)—10~(-4)M范围内,聚合物平均聚合度的倒数与叔胺浓度的0.5次方成正比。初步认为在紫外光激发下,芳香叔胺与丙烯腈分子生成激发态电子转移络合物,再分解产生自由基,引发丙烯腈聚合。

PHOTOPOLYMERIZATION OF ACRYLONITRILE INITIATED WITH AROMATIC TERTIARY AMINE

We have found that DMT would act as active initiator for the photopolymeriza-tion of acrylonitrile. The sensitization effect of various aromatic tertiary amines on the photoplymerization of AN has been studied. The electro-positive group on the benzene ring will increase the activity of the amine while the electro-negative group will decrease it. The activities of various amines have been found in the following decreasing order:N, N-dimethyltoluidine (DMT) >N, N-dmethyl-p-hydroxyethyltoluidine (DHET) > N, N-dimethylaniline (DMA) > N, N-dimethylamino ben zaldehyde (DMB) >N, N-dimethyl-p-nitroaniline (DNA).The mechanism of photoplymerization of AN initiated with aromatic tertiary amine belongs to the free radical type in nature, and the rate of polymerization is proportional to the 0.66th power of concentration of amine. Within the range of 10-2-10-4 M in the concentration of amine the reciprocal of average degree of polymerization is proportional to the 0.5th power of concentration of amine. The tentative mechanism of initiation has been proposed. The formation of initiating radical species may be ascribed to the decomposition of the excited charge transfer complex (exciplex) from the excited state of aromatic tertiary amine with the monomer molecule of acrylonitrile.