High molecular weight polyacetylenes hearing nonlinear chromophoric pendants poly [4-ethynyl-4'-(N,N-diethylamino)azobenzene-co-phenylacetylene]s [poly(EAAB-co-PA)s] were synthesized in moderate yields by [Rh(nbd)Cl](2)-Et3N. The azo unit in the copolymers call be effectively controlled by the monomer feed ratio. Whereas the homopolymer of EAAB possessed low solubility. all the copolymers, however, dissolved readily in common organic solvents when the poly(EAAB) molar content was less than 41.7%. The structures and properties of the polymers were characterized and evaluated by UV. NMR, optical limiting, and nonlinear optical analyses. All the copolymers possessed high stereoregularity and thermal stability ( 300 degrees C). They can attenuate intense laser pulses, With Solutions of high concentrations showing better performances. The third-order nonlinear Susceptibility of the copolymers was as high as 4.62 X 10(-11) esu, which are two orders of magnitude larger than those of poly(PA), and larger than that of poly(N-carbazoylacetylene), and poly(1-naphthylacetylene). (c) 2005 Elsevier Ltd. All rights reserved.