Chromatographic separation of azeotropic and low‐conversion poly(styrene‐stat‐2‐methoxyethyl methacrylate) according to chemical composition

摘要

AbstractDistribution of the chemical composition of statistical copolymers was studied by HPLC using azeotropic and low‐conversion copolymers of styrene and 2‐methoxyethyl methacrylate that are expected to exhibit only statistical chemical heterogeneity. Adsorption behavior of the copolymers was studied dynamically with a specially designed apparatus, using flow through a column packed with a macroporous silica and a mixed mobile phase 1,2‐dichloroethane (DCE)–heptane (50 : 50 v/v) and tetrahydrofuran (THF). The shape of displacement isotherms indicates the existence of a region lying near the displacement critical composition, where the total amount of adsorbed copolymer is independent of the mobilephase composition. Fractionation was achieved by step‐by‐step desorption of a copolymer sample previously adsorbed on silica packed into a chromatographic column, by means of a stepwise gradient of mobile‐phase composition. The styrene content of isolated fractions decreased with increasing content of THF in the mobile phase. The experimentally determined integral weight distribution of chemical composition shows good agreement with theoretical curves. © 1993 John W