Kinetics of the UV-Photopolymerization in TS Diacetylene Single Crystals as Studied by Time Resolved Optical Spectroscopy

Abstract

Abstract The intermediate products A, B, C, D, E and V of the UV initiated solid state polymerization in single crystals of 2,4 hexadiynylene bis (p-toluene sulfonate), particulary their kinetics, have been studied by time resolved optical absorption spectroscopy in the temperature range between 180 and 300 K. The description by a simple kinetic model states that A to E react in a direct sequence by monomer addition, which is thermally activated. The activation energies range from 0.25 to 0.30 eV per monomer. At 300 K the reaction rate constants are of the order of 106 s-1. - Product V is interpreted as a superposition of several long chain oligomers with reactive carbene chain ends. The reaction V → Polymer is thermally activated with an activation energy of 0,4 eV per monomer. - The fluorescence spectrum of the monomer crystal has been measured for the first time by use of a fast detection system. It is discussed with respect to its significance for the polymerization initiating step. - Deuterium isotope effects on the polymer absorption energy and on reaction kinetics are reported.