Mechanism of aging of poly[1-(trimethylsilyl)-1-propyne] and its effect on gas permeability

The effects of different mechanisms of aging of poly[1-(trimethylsilyl)-1-propyne] (PTMSP), namely, chemical aging (oxidation), physical and absorption aging, on gas permeability of the polymer were studied. For this purpose, the PTMSP samples obtained in the presence of various catalysts (TaCl5/BuLi, TaCl5/i-Bu3Al, and NbCl5) and stored at ambient temperature for 2–8 years were investigated. The procedure involving the stages of sequential dissolving, precipitation and recasting allowed us to recognize the contributions of different mechanisms of aging. It was shown that a long-term storage of PTMSP at ambient conditions results in oxidation of the polymer with formation of various functional groups (aldehyde, acid, ether, and epoxy groups). The dissociation of the main chain takes place as well with formation of low molecular mass products. It was shown, however, that is not the main reason for a reduction of gas permeability of PTMSP. The absorption aging of PTMSP provides the main contribution in decreases in gas permeability of aged PTMSP samples. Its consequences can be eliminated by the re-precipitation of the polymer from its solutions and subsequent recasting. Unusual behavior of aged PTMSP samples in separating of the C1–C3 hydrocarbons is also observed and discussed.