The prediction of reactivity in radical polymerisation

Until recently, the only method available for the prediction of monomer rea ctivity ratios in radical polymerisation was the Alfrey-Price Q-e Scheme. T his has now been adapted in such a way that all the scheme's undesirable fe atures have been removed and no assumptions are involved other than the bas ic separation of reactivity into thermodynamic and polar components. It is then found that, provided that the copolymerisation behaviour of any given monomer with (i) styrene and (ii) acrylonitrile has been characterised, its copolymerisation with any other monomer, similarly characterised, can be p redicted with much greater precision than hitherto. This procedure is calle d the Revised Patterns of Reactivity Scheme, or "Patterns". Unlike the Q-e Scheme, a parallel procedure can be applied to the prediction of transfer c onstants, with remarkable accuracy over a spread of transfer constant value s of nine orders of magnitude. The procedure can also be applied to evaluat e the reactivity of initiator radicals with monomers. A side-product of the Patterns scheme is a simple method for obtaining approximate values of the Hammett a constant for the substituent present on the a-carbon atom of a m onomer.