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 (k(p)) of alkyl acrylates by pulsed-laser polymerization (PLP). When the backbiting is the predominant chain transfer event, the apparent k(p) of acrylates determined in PLP experiments for different frequencies should range between k(p) (propagation rate coefficient of the secondary radicals) at high frequency and k(p)(av) at low frequency. The k(p)(av) value could be expressed from kinetic parameters: k(p)(av) = k(p) - k(p)-k(p2)/1+k(p2)[M]k(fp), where k(fp) is the <LF>backbiting rate coefficient, k(p2) 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 20degreesC. Horizontal full lines show the values of k(p) and k(p)(av).