IDENTIFYING THE NATURE OF THE ACTIVE SPECIES IN THE POLYMERIZATION OFMETHACRYLATES - INHIBITION OF METHYL-METHACRYLATE HOMOPOLYMERIZATIONSAND REACTIVITY RATIOS FOR COPOLYMERIZATION OF METHYL-METHACRYLATE N-BUTYL METHACRYLATE IN CLASSICAL ANIONIC, ALKYLLITHIUM TRIALKYLALUMINUM-INITIATED, GROUP-TRANSFER POLYMERIZATION, ATOM-TRANSFER RADICAL POLYMERIZATION, CATALYTIC CHAIN TRANSFER, AND CLASSICAL FREE-RADICAL POLYMERIZATION/

Reactivity ratios have been determined for the monomer pair methyl met hacrylate and n-butyl methacrylate under st range of polymerization co nditions. The value of using reactivity ratios as a mechanistic probe is discussed. Reactivity ratios determined where M1 = MMA and M2 = n-B MA are 1.04, 0.81, classical anionic; 1.10, 0.72, alkyllithium/trialky laluminium initiated; 1.76, 0.67, group transfer polymerization; 0.98, 1.26, atom transfer radical polymerization; 0.75, 0.98, catalytic cha in transfer; and 0.93, 1.22, classical free radical polymerization. Th e data suggest ATRP and CCTP proceed via radical type propagation. Li/ Al-initiated polymerization undergoes an anionic mechanism, while stro ng evidence is found for an associative, catalyst dependent mechanism for GTP. Galvinoxyl is demonstrated to inhibit GTP as well as free rad ical polymerization, and it is suggested that neither the use of inhib ition nor polymer stereochemistry can be used to distinguish between a nionic and radical processes.