Determination of the Microstructure of Some Methyl Methacrylate-Butadiene Copolymers by 220 MHz Proton Magnetic Resonance Spectroscopy

Abstract

Proton magnetic resonance (PMR) spectroscopy at 220 MHz has been used to gain information about the relative proportions of various methyl methacrylate centered triads and pentads in some methyl methacrylate (MMA)-butadiene (BU) copolymers prepared with a free-radical catalyst. The PMR peaks used are the MMA α-methyl peaks recorded using CDCL₃ as solvent, and the MMA α methyl peaks recorded using C₅D₅N as solvent. Measured triad and pentad fractions are in good agreement with those calculated from the reactivity ratios r₁ = 0.17 and r₂ = 0.60, where MMA = Monomer 1. Surprisingly, the α-methyl peaks provide information also about the ratio of cis-1,4- to trans-1, 4-butadiene units in the copolymer. Proportions of 1,2-butadiene units are obtained from the relative areas of peaks due to vinyl and vinylene protons.