Abstract: Poly(1-trimethylsilyl-1-propyne)(PTMSP) membranes were prepared by a solution-casting method in thickness ranging from 50 μm to 202 μm to study the effect of aging on their gas permeabilities. These membranes stored at room temperature display substantial decreases in gas permeability with time because of physical aging. The gas permeability decreased rapidly at first, and a slower, more gradual decrease and then almost leveled off was observed. PTMSP membrane stored in air exhibited slightly larger permeability decrement than that stored in N2. The decrease rate of gas permeability increased with the decrease of membrane thickness, and it decreased much more when the PTMSP membrane aged at high temperature of 100 ℃ in air, which is due to both physical aging and chemical aging. IR spectrum of the membrane indicates that storage of PTMSP at high temperature in air results in oxidation of the polymer with formation of C=O groups. The gas permeability coefficient(P) of the membrane was inspected in more detail by determining the gas diffusion coefficient(D) and gas solubility coefficient(S). The S value hardly changed during storage, whereas the D value decreased with aging, which is responsible for the decrease of gas permeability. The decrease of D can be explained by the elimination of fractional free volume due to the volume relaxation and/or densification and the formation of polar groups in the polymer.

Key words: substituted polyacetylene, gas permeation membrane, aging