Microstructure of the copolymers of methyl methacrylate with other methacrylates obtained by radical and anionic copolymerizations in tetrahydrofuran

Abstract

Abstract Monomer reactivity ratios r 1 and r 2 were determined in the copolymerizations of methyl methacrylate (MMA, M 1 ) with 1, 1‐diphenylethyl (DPEMA), α,α‐dimethylbenzyl (DMBMA), tert ‐butyl ( t ‐BuMA), diphenylmethyl (DPMMA), phenyl (PhMA), and 1‐naphthyl (NpMA) methacrylates ( M 2 ) in tetrahydrofuran (THF) by azobisisobutyronitrile (AIBN) at 60°C and butyllithium ( n ‐BuLi) at −78°C. The reactivities of the monomers were explained in terms of the polar effect of the ester groups in both copolymerizations. All the copolymers isolated in low yields were converted to PMMA either directly or by copoly(MMA—methacrylic acid) to determine the triad tacticities of the copolymers. Coisotactic parameters σ 12 and σ 21 were determined by assuming the terminal model statistics. The σ 21 values always accorded to the σ 21 values within experimental error, and in radical copolymerizations they were between isotactic parameters σ 11 and σ 22 of the homopolymerizations of MMA and M 2 monomers. In anionic copolymerizations, however, the σ 12 = σ 21 values varied, depending on the M 2 monomers. In copolymerization with DPEMA the values were less than both σ 11 and σ 22 with DMBMA they were between σ 11 and σ 22 , with DPMMA, nearly equal to σ 11 , and with PhMA and NpMA, greater than both σ 11 and σ 22 . The application of these parameters to copolymerizations performed at high conversion was also investigated.