Four-center type photopolymerization in the solid state. I. Polymerization of 2,5-distyrylpyrazine and related compounds

Crystalline 2,5-distyrylpyrazine (DSP) was found to polymerize into a linear high polymer with extremely high crystallinity by the action of sunlight or ultraviolet light. Based on this discovery, photopolymerizability of the related diolefins having the general formula, trans,trans-Ar′? CH?CH? Ar? CH?CH? Ar′ was surveyed. As a result, 1,4-bis[β-pyridyl-(2)-vinyl]benzene (P2VB) was found to polymerize in the same way as DSP. The polymers as polymerized, showed a high melting temperature (>330°C) and were soluble only in strong acids. The structure of the polymers was investigated by means of several customary methods involving infrared and NMR spectrum studies. It was concluded that both poly-DSP and poly-P2VB consist of a linear structure having a recurring cyclobutane ring in the main chain. General properties of this novel polymer were studied.