Reaction kinetics of polymer substituents containing two reactive groups

Abstract

A model has been examined in which the substituents of a polymer each contain two reactive groups, A and B. Reaction can occur at random between A of one substituent and B of either (but not both) of its two neighbouring substituents, so as to form a ring structure; in consequence, pairs of A or B groups on adjacent substituents become isolated on contiguous ends of separate sequences of the ring structures. Expressions are derived giving as functions of time, (a) the number N_x of sequences containing 2x unreacted groups, (b) the extent ξ of reaction and (c) the rate ξ of reaction. At the end of reaction the number of isolated groups agrees with that calculated by Flory and by Wall. The behaviour of the model is compared with that of an earlier model with simple pairing between substituents. Reactions suitable for experimental investigations are discussed, and a comparison is made of the theory with some results of Grassie and Hay for the thermal decomposition of polymethyl vinyl ketone.