Determination of Propagation Rate Coefficient of Acrylates by Pulsed-Laser Polymerization in the Presence of Intramolecular Chain Transfer to Polymer

Unusual difficulties are faced in the determination of propagation rate coefficients (kp) of alkyl acrylates by pulsed‐laser polymerization (PLP). When the backbiting is the predominant chain transfer event, the apparent kp of acrylates determined in PLP experiments for different frequencies should range between kp (propagation rate coefficient of the secondary radicals) at high frequency and k pav at low frequency. The k pav value could be expressed from kinetic parameters: $k_{\rm p}^{{\rm av}} = k_{\rm p} - {{k_{\rm p} - k_{{\rm p}2} } \over {1 + {{k_{{\rm p}2} [{\rm M}]} \over {k_{{\rm fp}} }}}$, where kfp is the backbiting rate coefficient, kp2 is the propagation rate coefficient of mid‐chain radicals, and [M] is the monomer concentration. Apparent propagation rate coefficients determined for different frequencies by simulating the PLP of n‐butyl acrylate at 20 °C. Horizontal full lines show the values of kp and k pav.