Thermal and photoinduced polymerization of thin diacetylene films. 1. Phthalimido-substituted diacetylenes

A series of phthalimido-substituted (Pht) diacetylenes with the structure P ht-(CH2)n-C drop C-C drop C-(CH2)(m)-R was synthesized. The influence of th e length of the alkyl spacer n between the phthalimido group and the diacet ylene group, the length of the alkyl spacer In and an additional polar grou p R on the thermal and UV-induced polymerization was investigated by system atic variation of n, m, and R (for R = H and m = 8, n = 1, 3, 4, 5, 8, 9; f or n = 9 and In = 3, R = H, CH2OH, COOH) All synthesized compounds underwen t thermal polymerization. The polymerization temperature increased with lon ger n spacer or shorter m spacer, and no effect was observed on variation o f R. For UV-induced polymerization, a spacer length n of more than four car bon atoms was necessary, introduction of a hydrogen-bond-forming hydroxyl o r carboxyl group at the other side of the diacetylene yielded polymers with a significantly higher degree of conjugation and also improved film format ion on quartz enormously.