TRANSFER CONSTANTS FROM COMPLETE MOLECULAR-WEIGHT DISTRIBUTIONS

Transfer constants to chain-transfer agent (CTA) and to monomer can be obtained by consideration of the complete molecular weight distributi on, using the slope of a plot of the natural logarithm of number-molec ular weight distribution against molecular weight, in the limit of hig h molecular weight and low radical flux (P. A. Clay, R. G. Gilbert, Ma cromolecules 28, 552 (1995)). This method is applied to the bulk polym erisations of methyl methacrylate (MMA) with added triethylamine (TEA) and with added tert-dodecylmercaptan (mixture of 2,4,4,6,6-pentamethy lheptane-2-thiol and 2,2,4,6,6-pentamethylheptane-4-thiol, TDM). The t ransfer rate coefficients are found to be 74 (+/- 20) dm(3) . mol(-1). s(-1) at 60 degrees C for TEA, and 56 (+/-13) dm(3) . mol(-1). s(-1) at 25 degrees C for TDM.