Determination of Compositional Distribution as a Function of Molecular Size for Styrene-Methyl Methacrylate Random Copolymers by Liquid Adsorption Chromatography and Size Exclusion Chromatography

摘要

Low- and high-conversion styrene-methyl methacrylate random copolymers, P(S-MMA), were fractionated by size exclusion chromatography (SEC). Each fraction was subjected to liquid adsorption chromatography (LAC) using silica gel as an adsorbent and a mixture of chloroform and ethanol as the mobile phase. In low-conversion P(S-MMA), the differences of peak composition of LAC chromatograms for SEC fractions were 4-5% and the difference between the highest and the lowest styrene content in components was about 10%. CCD became broader with decreasing molecular size. One sample of low-conversion P(S-MMA) showed two peaks in a LAC chromatogram, showing that this sample was a mixture of two copolymers of different compositions. LAC peaks of SEC fractions for high-conversion P(S-MMA) were broad compared to low-conversion ones; the difference of peak composition for one sample was 11% and the range of composition was between 21 and 52% styrene. LAC is a very useful technique for obtaining CCD of copolymers and compositional differences in a sample.