TOWARDS THE PROPAGATION RATE COEFFICIENT FOR THE FREE-RADICAL POLYMERIZATION OF 1,3-BUTADIENE

The propagation rate coefficient k(p) for the free-radical polymerizat ion of 1,3-butadiene was determined as a function of temperature in th e range of 30-60 degrees C in bulk and as a function of the concentrat ion of 1,3-butadiene in chlorobenzene at 50 degrees C using a combinat ion of a UV flash-lamp induced polymerization and a measurement of the molecular weight distribution of the produced polymer by size exclusi on chromatography. Differences of up to around 45% resulted even for t he same concentrations and temperatures when these measurements were c ompared with recent determinations of k(p) of 1,3-butadiene in chlorob enzene in which just such an experimental setup was used. This finding was essentially attributed to large differences in the radical termin ation rates which prevailed in the reaction volumes under the current conditions of the pulse-induced polymerization experiments. Moreover, in the vicinity of bulk concentrations of 1,3-butadiene in chlorobenze ne, k(p) apparently decreases with concentration.