Synthesis and gas permeability of nitrated and aminated Poly(diphenylacetylene)s

- We achieved the nitration of poly(diphenylacetylene)s having various substituents.
- Reduction proceeded quantitatively to afford aminated poly(diphenylacetylene)s.
- The aminated poly(diphenylacetylene)s exhibited CO2 permselectivity.
- The amination of polymer with t-Bu increased both CO2 permeability and selectivity.

Poly(diphenylacetylene) [PDPA] derivatives were nitrated using a mixture of nitric acid and sulfuric acid. Nitration of poly[1-(p-trimethylsilyl)phenyl-2-phenylacetylene] (1a) proceeded, and the nitro groups were substituted to trimethylsilyl groups on benzene rings. The degree of nitration (DN) increased with reaction time, and it reached 0.41 for 3.0 h. Fluorine-containing PDPA (1b and 1c) showed less reactivity for nitration, and the DNs were only 0.18 and 0.06, respectively, under the same conditions. Nitration of PDPAs having n-butyl and t-butyl groups (1d and 1e) afforded the nitrated PDPAs, whose DN were 0.20 and 0.14, respectively. Reduction of nitro groups on PDPAs proceeded quantitatively to produce the corresponding PDPAs possessing amino groups (3a-e). Aminated PDPAs exhibited high CO2 permselectivity compared to the corresponding non-aminated PDPAs. The CO2 permeability coefficients of aminated PDPAs (3a-d) were lower than those of the corresponding polymers (1a-d) because the polymer chain packing was strengthened by the intermolecular interaction between polar amino groups, but t-butyl group-containing aminated PDPA (3e) showed high CO2 permeability than 1e because the chain packing was weakened by the steric repulsion of bulky t-butyl groups.

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