Preparation and property of two soluble oxadiazole-containing functional polyacetylenes Part A Polymer chemistry

Two novel high-molecular weight functional polyacetylenes (PA) bearing oxadiazole group as a pendant, poly(2-(4-octoxyphenyl)-5-(4-ethynylphenyl)-1,3,4-oxadiazole) (P1) and poly(2-(4'-octoxyphenyl)-5-(4'-propynyloxyphenyl)-1,3,4-oxadiazole) (P2) were synthesized by [Rh(nbd)Cl]₂-Et₃N catalysts. Both polymers were soluble in common organic solvents such as CHCl₃ and tetrahydrofuran. Their structures and properties were characterized and evaluated with FTIR, NMR, UV, thermogravimetric analysis, GPC, optical-limiting and nonlinear optical analyses, respectively. The results show that linkage of oxadiazole chromophore to PA main chain has improved the nonlinear optical (NLO) property of PA, and endowed PA with novel optical limiting properties and enhanced thermal stability. Simultaneously, the optical-limiting and NLO properties of the polymers were sensitive to their molecular structures. P1 with oxadiazole directly incorporated into PA main chain as a pendant showed better performances and larger third-order nonlinear optical susceptibility than P2 with oxadiazole incorporated into PA main chain via a spacer.