A gravimetric and Spectroscopic Study on the Photoinduced Radical Co-polymerisation of Methyl and Allyl Methacrylates: Kinetic and Structural Properties.

Abstract

The photoinduced radical co-polymerisation of methyl and allyl methacrylates has been monitored by gravimetric analysis, Fourier Transform infra-red (FTIR) and FT nmr spectroscopy using a range of different photofragmenting and hydrogen atom abstracting type initiators. Using both visible and UV light sources the rates of photo-co-polymerisation were found to follow similar trends in both bulk and solution phase. Furthermore, unlike thermal polymerisation wherecrosslinking can occur through the allyl group, only the acrylate double bonds undergo reaction to produce a copolymer. GPC analysis showed that the homopolymers produced had narrower polydispersities than those of the copolymers while the photofragmenting type photoinitiators produced polymers with lower number average molecular mass than those produced via a hydrogen atom abstracting type. The latter is associated with marked differences in the degree of self-termination by initiator fragments. Structural analysis of the homo and copolymers by 1H FT nmr showed that photoinduced polymerisation produce polymers with a greater degree of stereoregularity than those obtained by conventional thermal radical initiation. Thus, the initiating process appears to play a major role in controlling the orientation of propagating chains.