INFLUENCE OF CHEMICAL HETEROGENEITY OF COPOLYMERS ON THE SEPARATION PROCESS IN SIZE-EXCLUSION CHROMATOGRAPHY

The effect of the chemical-composition heterogeneity of flexible-chain binary copolymers on their separation in size-exclusion chromatograph y (SEC) was theoretically examined. The two parameter theory of polyme r solutions was engaged to estimate the coil size. The variation in mo lecular weight is shown for copolymer molecules which differ in the ra tio of the two constituent monomeric units but have the same coil size and, therefore, are eluted at the same elution volume. The result was applied to a theoretical case of analysis of copolymers, the composit ion and molecular-weight distributions of which are given by theoretic al functions. If the refractive index increments of homopolymers whose units constitute the copolymer are equal or close to each other, the influence of the chemical heterogeneity on the experimental data is be low the experimentally detectable limit. A significant error in the de termination of the molecular-weight averages can occur only if the dif ference in the refractive index increments exceeds physically reasonab le limits.