Synthesis and optical properties of azobenzene-containing poly(1-alkyne)s with different spacer lengths and ring substituents

Poly(1-alkyne)s containing azobenzene pendants with different spacer lengths and ring substitutents –{HCC[(CH2)mCOO–C6H4–NN–C6H4–NO2]}n– P1(m) m=3, 8 and –{HCC[(CH2)mCOO–C6H3-o-Br–NN–C6H4–NO2]}n– P2(m) m=3, 8} are designed and synthesized. The polymers are prepared in satisfactory yields with high molecular weights (Mw up to 3.3×104 Da) by [Rh(nbd)Cl]2–Et3N in THF or dioxane. Their structures and properties are characterized and evaluated by IR, UV, NMR, TGA, nonlinear optical and optical limiting analyses. All the polymers are completely soluble in common organic solvents and lose 5% of their weights at temperatures of ∼270 °C. The spacer length and the pendant substitutent affect the nonlinear optical and optical limiting properties of the polymers, with 1(3) showing superior properties than its counterparts 1(8) and 2(3) with long methylene spacers and bromide substitutents on the azobenzene pendants, respectively.