Synthesis and CO2 permeation properties of novel sulfonium-substituted poly(diphenylacetylene)s

Abstract

Substitution of thiourea to poly(diphenylacetylene) having 2-bromoethoxy groups (2a) gave an sulfonium-containing poly(diphenylacetylene) [3a (Br − )]. The counteranions of 3a (Br − ) could be exchanged using CF3COOK and (CF3SO2)2NLi, and the polymers 3a (TFAc − ) and 3a (Tf 2 N − ) were obtained. Polymer 3a (Br − ) was hydrolyzed with NaOHaq to afford the polymer 4a possessing mercapto groups. The CO2 permeability coefficients (\(P_{{{\text{CO}}_{ 2} }}\)) and the separation factor (\(P_{{{\text{CO}}_{ 2} }} /P_{{{\text{N}}_{ 2} }}\)) of 3a (Br − ) were 15 barrers and 16, respectively. The selectivity was low compared to the analogous polymer, poly(diphenylacetylene) having imidazolium salts (\(P_{{{\text{CO}}_{ 2} }} /P_{{{\text{N}}_{ 2} }} = 4 4\)), because 3a (Br − ) interacted strongly with CO2, and the diffusion of CO2 was suppressed. The \(P_{{{\text{CO}}_{ 2} }}\) and \(P_{{{\text{CO}}_{ 2} }} /P_{{{\text{N}}_{ 2} }}\) of 3a (TFAc − ) were 43 barrers and 24, respectively, and those of 3a (Tf 2 N − ) were 52 barrers and 26, respectively. Both permeability and selectivity increased as the counteranion became bulkier. The mercapto group containing poly(diphenylacetylene) (4a) showed a relatively high CO2 permeability (\(P_{{{\text{CO}}_{ 2} }} = 1 30\) barrers).