COPOLYMERIZATION PROPAGATION KINETICS OF STYRENE AND METHYL-METHACRYLATE - REVISITED - 1 - PULSED-LASER POLYMERIZATION STUDY

A comprehensive set of propagation rate coefficients for styrene-methy l methacrylate bulk copolymerization has been obtained from pulsed las er polymerization experiments performed over a range of temperatures ( 18-57 degrees C). The copolymer molecular weight distributions were an alyzed using size exclusion chromatography with on-line low-angle lase r-Light scattering (LALLS) and differential viscometry (DV) detectors. The molecular weight data obtained using these absolute detection met hods were compared with data obtained by assuming the copolymer hydrod ynamic volumes (HDVs) can be described by a weighted average of the ho mopolymer HDVs. The analyses via these three different approaches yiel ded virtually identical molecular weight data, validating previous wor k on this copolymerization system. The precision of the data obtained from LALLS and DV was worse than that obtained from the HDV-weighted a pproach. However, the errors in the molecular weight data from DV and LALLS analyses are believed to be a more correct representation of the true errors in the molecular weight measurement. A strategy for reduc ing the effect of the molecular weight errors in the (k) over bar(p) m easurements, via the selection of slow laser flashing rates, is presen ted.