Effect of Repetition Rate on the Pulsed-Laser-Initiated Polymerization of a Liquid-Crystalline Monomer

The use of high repetition rate laser pulses for the photoinitiated polymerization of a cholesteryl-bearing methacrylate liquid crystalline monomer has been investigated. In the case of polymerization in the isotropic phase, the molecular weight and yield of the polymer generated decreased with a decrease in time between firing of individual laser pulses. This phenomenon is in accordance with all previously reported results for isotropic monomers. However, polymerization in the smectic phase of the monomer was not affected by the laser repetition rate. It is postulated that for pulsed-laser-initiated polymerization in the smectic phase the rapid termination process of coupling of primary and short chain oligomeric radical terminator species with growing polymer radical chains, normally found for radical polymerization of isotropic monomers, is greatly reduced