Inverse Gas Chromatography on Graft and Random Copolymers of Styrene and 2-Hydroxyethyl Methacrylate

Abstract

ABSTRACT:Inverse gas chromatography (IGC) was applied to amphiphilic graft copolymers of poly(2-hydroxyethyl methacrylate) (PHEMA) with polystyrene (PSt) branches using various probes at 160°C. Retention oftetradecane or amylbenzene, which selectively interacts only with PSt phase, suggested that a microphase inversion occurs around 20-30wt% PSt, below which PSt segments constitute a discontinuous phase (islands). Rather nonselective probes such as dimethylformamide and 2-(2-methoxyethoxy)ethanol showed a retention which exceeds that expected from a simple additive relation, suggesting a considerable contribution of their interaction with the interface of the microphase-separated domains. In contrast, random copolymers showed a retention behavior as expected for a statistical distribution of the monomer units. General discussion is given on IGC as a means of characterizing binary polymer systems.KEY WORDS Inverse Gas Chromatography I Amphiphilic Graft Copolymer I 2-Hydroxyethyl Methacrylate I Styrene I Microphase Separation I Morphology I Selective and Nonselective Probes I Inverse gas chromatography (IGC) has been developed by Guillet and others1.2 as a simple and convenient method for evaluating various properties of polymers such as melting point (Tm), glasstransition point (Tg), crystallinity, interaction parameter, and solubility parameter. In principle, it relies on the interaction of an appropriate volatile compound as a probe with a target polymer as a stationary phase in conventional gas chromatography. Since any change in polymer phase would be reflected in the retention behavior of a probe, IGC also appears to be useful as a method for examining a multi-phase structure in block or graft copolymers and in polymer blends, in addition to being a simple method of evaluating their interaction with the probe. Galin and Rupprecht 3 investigated the retention of decane on polystyrene (PSt)-polydimethylsiloxane (PDMS) block copolymers to estimate the domain size of PSt. Ward et a/. 4 similarly evaluated the morphology of PDMSbisphenol A polycarbonate block copolymers and blends. Decane as a probe was assumed in these cases to interact independently with the PDMS matrix and surface (interface) of PSt-or polycarbonate domains at a temperature below their Tg. Suzuki et a/. 5 studied the surface morphology of PSt-poly(ethylene oxide) blend by following the retention behavior of octane in comparison with scanning electron-microscope observation.We also examined a retention of dodecane on PSt-polytetrahydrofuran (PTHF) block copolymers6 and on poly(methyl methacrylate) (PMMA}-poly(stearyl methacrylate) (PSMA) graft copolymers7 to show that PTHF or PSMA segments, which have a lower Tm and a lower surface-energy, tend to make a continuous phase as compared to PSt or PMMA segments, respectively. In general, the IGC method may be expected to give more clear-cut and interesting information on the morphology of these multi-phase polymer systems by analyzing the retention behavior of several probes which may interact selec...

Syntheses and interfacial characterization of graft copolymers from styrene and 2-hydroxyethyl methacrylate that comprise either trunks or branches

“…5. On the other hand, a random copolymer prepared by copolymerization of styrene and HEMA was found to show a normal spectrum even in a single selective solvent (3), indicating that the statistical distribution of styrene and HEMA units with very short sequence lengths prevents rnicelle formation. Wettability of graft copolymer films Surface properties of the graft copolymers were evaluated most conveniently by the measurement of the contact angle of water on polymer films cast from appropriate solvents.…”

“…est because the hydrophilic and hydrophobic chains incorporated into either the trunk or the branch will segregate into the respective microdomains via microphase separation to exert interesting surface-or interface-active behavior. Previously, we reported a graft copolymer, PHEMA-g-PS, with poly(2-hydroxyethyl methacrylate) (PHEMA) as the trunk and polystyrene (PS) as the branch, prepared by copolymerization of 2-hydroxyethyl methacrylate (HEMA) and the PS macromonomer with a methacrylate end group (3). The same graft copolymer has been evaluated as a blood-compatible, selfreinforced hydrogel by Yamashita et al (4).…”