Determining the Q–e values of polymer radicals and monomers separately through the derivation of an intrinsic Q–e scheme for radical copolymerization

Abstract

Herein, we describe the first non-arbitrary determination of the Q–e values for individual polymer radicals and monomers. For this purpose, two reference monomers were subjected to a Q–e scheme, which was extended by including the individual radical and monomer parameters to derive a novel scheme, namely the intrinsic Q–e scheme. The derivation of this scheme was straightforward and was expressed only through the reactivity ratios among a target monomer and the reference monomers. The expression of the reactivity ratios by the scheme was found to be equivalent to that of the revised patterns A,S scheme, indicating the excellent predictability of the reactivity ratios. We then employed the intrinsic Q–e parameters to successfully calculate the Q–e values of individual radicals and monomers. A relatively good correlation was observed between the radical and monomer Q values (Q_R and Q_M, respectively), while no clear correlation was observed between the radical and monomer e values (e_R and e_M, respectively), as some of them significantly deviated from the condition e_R = e_M or had different signs. Therefore, the approximation of e_R = e_M in the original Q–e scheme is not necessarily valid in some cases. Since the Q_M–e_M values correlate well with Greenley's Q–e values, they are both suitable as indicators of the monomer properties. Finally, application of the intrinsic Q–e scheme to transfer constants for transfer agents is also described.