Solute diffusion in polymers. I: The use of capillary column inverse gas chromatography

• Published in: Macromolecules 1987-07, Vol.20 (7), p.1564-1578
• Main Authors: PAWLISCH, C. A, MACRIS, A, LAURENCE, R. L
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Solution and gel properties
• ISSN: 0024-9297; 1520-5835

A technique using inverse gas chromatography (IGC) for accurately measuring polymer-solute diffusion coefficients has been developed. The technique is ideal for studying interactions of volatile materials with molten or rubbery polymers, at conditions approaching infinite dilution of volatile component. Previous efforts used to measure diffusivity via a chromatographic technique have used packed columns, with polymer supported as a thin, irregular coating on the packing. The irregularity of the coating severly limits measurement accuracy. This difficulty is overcome by using a capillary column with a relatively thick, uniform coating, which admits more realistic mathematical models for parameter estimation. The polymer, the stationary phase in the experiment, is deposited as a uniform annular coating on the inside of a glass capillary column. A solute is injected into an inert carrier gas flowing through the column. The elution characteristics of the sample (residence time and shape of the elution curve) are used to determine the solute activity and diffusivity in the stationary phase. The validity of the technique was demonstrated by measuring the diffusivity and activity of benzene, toluene, and ethylbenzene in polystyrene between 110-140 deg C. The thermodynamic properties obtained were in good agreement with existing packed-column IGC and vapor sorption data. The diffusion coefficients obtained were consistent with existing vapor sorption measurements. 48 ref.--AA