Chemical modification of poly(substituted‐acetylene). I. Synthesis and gas permeability of poly(1‐trimethylsilyl‐1‐propyne)/poly (dimethylsiloxane) graft copolymer

In order to improve the selectivity and the stability and the stability for gas permeation of poly (1-trimethylsilyl-1-propyne) (PTMSP) membrane, it was chemically modified by grafting polydimethylsiloxane (PDMS) chains. The graft copolymers were synthesized by four different methods via metallation of PTMSP with n-butyllithium. PDMS content of the graft co-polymers was controlled in the range of 4–92 mol %. Very tough, thin membranes could be prepared from these graft copolymers using a solvent casting method. Thermal property and gas permeability of the copolymer membranes thus obtained were evaluated. These membranes were relatively thermally stable, and the softening points were over about 150°C. Oxygen permeability coefficients Po2 and selectivity Po2/PN2 of PTMSP/PDMS graft copolymers depended on the PDMS content, the former was in the range of 1 X 10−8 to 2 × 10−7 cm3 (STP)· cm/(cm2· s · cm. Hg) and the latter was 2.0–3.1. Minimum values of PO2 and PN2 occured at PDMS content of about 55 mol %. The introduction of more than 60 mol % of PDMS resulted in oxygen permeability coefficient which was maintained for more than one moth (PO2 = 2 − 6 × 10 −8 cm 3 (STP)· cm/(cm2·s·cm Hg), PO2/PN2 = 2.3–2.7).