Gas solubility and diffusion in a polystyrene–polybutadiene block copolymer

✍ Scribed by D. H. Rein; R. F. Baddour; R. E. Cohen

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 295 KB
• Volume: 45
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/app.1992.070450711

✦ Synopsis

Over the temperature range of 20 to 90°C, the equilibrium solubility of methane or argon in a star-branched polystyrene-polybutadiene ( SB ) block copolymer can be reliably estimated from a volume-fraction-weighted average of the homopolymer solubilities; the value of heat of solution for SB block copolymer lies between the two values associated with the constituent homopolymers. Diffusion coefficients for gases in the block copolymer are bracketed by the homopolymer values over the range of temperature employed, but the activation energies for diffusion in SB are higher than either of the homopolymer values. The anomalous temperature dependence and the inability of a computer simulation to reproduce experimental diffusion coefficients supported the concept of a temperature-dependent restriction on chain mobility in the polybutadiene regions of the block copolymer. This @ factor embodies the relative reduction in the rate of gas diffusion through the B regions of the copolymer compared to B homopolymer; / 3 has a value of about 2-3 at room temperature but decreases to unity when the polystyrene chains become mobile at the polystyrene T8.