Gas Transport in Polybutadiene Treated with Aqueous Bromine

摘要

Diffusion, solubility and permeability coefficients were measured for He, CO2, Arand CH4 in polybutadiene (PB) and in polybutadiene reacted in the solid state to various extents with aqueous bromine. Analysis of the sorption curves and x ray emission spectra showed that the bromination created a heterogeneous membrane with an outer brominated skin and an unreacted core. At relatively low extent of bromination, the diffusion and permeability coefficients for CO2, Ar and CH4 became immeasurably small after about 3% bromination. The ideal separation factor for gas pairs with different molecular size increased with bromination, suggesting applications in gas separation processes. Tailoring the structure of existing commodity polymers through chemical modification is an attractive approach to improving the properties of membranes for gas separation and barrier applications. Systematic alterations of the polymer structure also provide a convenient route for studying the effects of molecular architecture on the permeability. Substitutions to the backbone or side chains affect the intrasegmental mobility and intersegmental chain packing, resulting in changes in gas diffusivity, solubility and permeability coefficients.