NMR-STUDIES OF FREE-RADICAL POLYMERIZATION AND COPOLYMERIZATION OF MONOMERS AND POLYMERS CONTAINING ALLYL GROUPS

Reactivity ratios for free-radical copolymerization of allyl acetate (A) with (i) methyl methacrylate (M), (ii) n-butyl acrylate (B) and (iii) styrene (S) have been evaluated from either copolymer compositions or dyad fractions determined by H-1 and C-13-NMR spectroscopy; the values obtained are respectively: (i) r(A) = 0.024 +/- 0.009 and r(M) = 41 +/- 6, (ii) r(A) = 0.04 +/- 0.02 and r(B) = 11.7 +/- 1.0, and (iii) r(A) = 0.021 +/- 0.001 and r(S) = 66 +/- 4. These values indicate that in copolymerizations of ally] methacrylate with (meth)acrylates and styrene, conversion of the allylic C=C bonds will only become significant when the extent of reaction of all other types of C=C bonds has reached very high values. NMR studies o the structure of poly(allyl methacrylate) formed by both bulk and dilute solution polymerization have provided no evidence for the in-chain lactone rings which may result from intramolecular cyclopolymerization of allyl methacrylate; the signals in the NMR spectra of poly(allyl methacrylate) are entirely consistent with ''normal'' polymerization at the methacrylic and allylic C=C bonds. Theoretical predictions based upon the measured reactivity ratios, and results from a model reaction, indicate that the very low concentrations of pendant methacrylic C=C bonds which result from polymerization of the allylic C=C bonds in molecules of allyl methacrylate, make a significant contribution to grafting and crosslinking.