Kinetics of anthracene addition to polystyrenes possessing one or two living ends per chain. Physical associations of the anthracenated polymer with a living end

Abstract

The kinetics of the addition of anthracene to living polystyrene has been investigated. Two types of polymers have been studied: those possessing one active end per chain and others endowed with two active ends in each polymeric molecule. The addition is rapid (rate constant of 10³-10⁴ l./mole sec), but anthracene A has to compete with the resulting product, [graphic omitted]S. A^–, M⁺ for the active ends, viz.,[graphic omitted] The association of [graphic omitted]S^–, M⁺ with [graphic omitted]SA^–, M⁺ is physical in nature, the spectrum of the associate being a superposition of the spectra of its components. Nevertheless, the associated living end is extremely unreactive, and its addition to anthracene is by several powers of 10 slower than that of the free living end. The kinetics of this slow reaction have also been investigated.

Intermolecular association takes place in systems involving one-living-end polymers, while those possessing two ends per chain undergo an intramolecular association which is faster than the intermolecular reaction. The intermolecular association is not diffusion controlled (k= 10³– 10⁴, and not 10¹⁰) which indicates the need of activation energy for the physical process. It is probable that the desolvation of the living ends, imperative for the association, is the source of the activation energy.

The effects of counterions and degree of ionization on the rates of addition have been determined.