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

Abstract

AbstractIn 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).