Synthesis and oxygen permselectivity of copoly(substituted acetylene)s with bulky fused polycyclic aliphatic groups

Abstract

Abstract We synthesized six phenylacetylenes (RCOPAs, RSOPAs, and RSPAs) having a bulky fused polycyclic aliphatic group, which is adamantyl(Ad), pinanyl(Pi), or cholesteryl(Ch) via oxycarbonyl (CO) or oxydimethylsilyl(SO), and the other two phenylacetylenes having less or non-bulky substituents, i.e., menthyloxycarbonylphenylacetylene (MtCOPA) or ethoxydimethylsilylphenylacetylene (EtSOPA) (Et = Ethyl). The new monomers were polymerized and copolymerized with p-trimethylsilylphenylacetylene (SPA) by using catalyst [Rh(nbd)Cl]2 (nbd = 2,5-norbornadiene) in trimethylamine to give soluble high molecular-weight polymers in relatively good yields. The resulting copolymers were fabricated to self-supporting membranes which had enough strength for separation membranes by solution casting method. As a result, we can discuss the relationship between bulky chemical structures and permeation behavior systematically for the first time. Oxygen permselectivities (PO2/PN2) of copolyRSOPAs having the bulky fused polycyclic aliphatic groups such as Ad and Pi were higher than those of copolyEtSOPAs. PO2/PN2 values of copolyRCOPAs were higher than those of polyRSOPAs when they had the same content of the identical bulky groups. The rigid spacer was effective for enhancing PO2/PN2. Among copolyRCOPAs with bulky fused polycyclic aliphatic groups, the copolymers with spherical substituents such as Pi and Ad groups showed higher PO2/PN2 values than those with a planer substituent i.e., Ch groups. PO2 values of copolyRSOPAs and copolyRCOPAs were 130–220 and 50–90 barrer, respectively. The flexible silyloxy spacers in RSOPAs were effective in enhancing their PO2 values.