Kinetic Model of Pulsed Laser-Initiated Polymerization in the Presence of Chain Transfer to Monomer

Abstract

Taking account of chain transfer to monomer, the kinetics of pulsed laser-initiated polymerization was treated in this article. The molecular weight distribution function and the expressions of number- and weight-average degrees of polymerization for the resulting polymer were derived under pseudostationary state conditions. Theoretical analysis and numerical calculation demonstrate that the presence of monomer transfer results in a narrower molecular weight distribution. With the increasing chain transfer rate constant, the polydispersity index of the resulting polymer decreases and finally approaches 2. Values of average degrees of polymerization and the polydispersity index vibrate between maxima and minima periodically, and the amplitude of the vibration declines with the increasing monomer conversion. The molecular weight distribution curves from numerical calculation show characteristic sharp peaks, and chain transfer to monomer weakens the intensity of peaks except the low molecular weight side one. Termination by combination leads to a little narrower molecular weight distribution, and so does the low concentration of the primary radical generated by per laser pulse.