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 distribution, using the slope of a plot of the natural logarithm of number-molecular weight distribution against molecular weight, in the limit of high molecular weight and low radical flux (P. A. Clay, R. G. Gilbert, Macromolecules 28, 552 (1995)). This method is applied to the bulk polymerisations of methyl methacrylate (MMA) with added triethylamine (TEA) and with added tert-dodecylmercaptan (mixture of 2,4,4,6,6-pentamethylheptane-2-thiol and 2,2,4,6,6-pentamethylheptane-4-thiol, TDM). The transfer 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.