Characterization of glycidyl methacrylate based copolymers by inverse gas chromatography under finite surface coverage

Abstract

Inverse gas chromatography under finite surface coverage conditions (IGC-FC) was used for the investigation of sorption of hexane, benzene, chloroform and tetrahydrofuran on macroporous crosslinked poly[(glycidyl methacrylate)-co-(ethylene glycol dimethacrylate)], poly(GMA-co-EGDMA), and copolymer modified with ethylene diamine, EDA, poly(GMA-co-EGDMA)-en, in the temperature range 333-363 K. Two poly(GMA-co-EGDMA) samples with different porosity parameters were synthesized by suspension copolymerization and modified using a ring-opening reaction of the pendant epoxy groups with EDA. The specific surface areas of the initial and modified copolymer samples were determined by the BET method from low temperature nitro- gen adsorption isotherms (77 K). The adsorption isotherms determined from chromatographic peaks of adsorbates were analyzed using the BET theoretical model and used for estimation of the surface area, isosteric heat of adsorption and the adsorption energy distribution on the surface of the initial and modified copolymer samples. It was observed that the adsorbate nature and the properties of the solid surface of the initial and modified copolymer governed the uptake of adsorbate by the copolymer. The deviations observed for the Sa values obtained by the BET method from the low temperature nitrogen adsorption isotherms and hexane was attributed not only to the difference in molecule size, but also to the specific polymer-adsorbate interactions. The isosteric heat of adsorption approached a constant value with increasing adsorbate loading. A large variation in the shapes of the q(st)-alpha curves resulted from strong acid-base interactions, as well as dissolution phenomena. Of the four studied adsorbates, chloroform was shown to have the greatest affinity towards the surface of the investigated polymer samples.