CHARACTERIZATION OF RANDOM COPOLYMERS BY SIZE EXCLUSION CHROMATOGRAPHY WITH A LIGHT-SCATTERING DETECTOR

Measurement of the molecular weight and molecular-weight distribution of copolymers by size exclusion chromatography (s,e.c.) can be difficult because of the lack of appropriate samples for calibration of the column. Comparison of copolymers of varying composition is even more problematic. The recent development of light scattering detectors for s.e.c. permits direct measurement of the molecular weight as the polymer elutes from the column, so that no calibration is necessary. A series of six copolymers of poly(4-(acetoxymethyl)styrene-co-4-(t-butyloxycarbonyloxy)styrene) have been measured, ranging in composition from 5 to 100 mol% of the poly(4-(acetoxymethyl)styrene). The differential refractive index increment varied linearly with composition. The weight-average molecular weights (M(W)) determined by s.e.c. with the light scattering detector agree well with those determined with light scattering alone. Application of the technique to copolymers is discussed.