A novel acetylene monomer containing benzoxazine group was synthesized and polymerized with [(norbornadiene)rhodium(l) chloride](2) ([(nbd)RhCl](2)) to give the corresponding polymer. The effect of triethylamine as co-catalyst in the polymerization was investigated. The spectral and thermal analyses confirmed the presence of benzoxazine functionality in the resulting polymer. It is shown that polyacetylene containing benzoxazine side groups undergoes irreversible cis-trans isomerization and thermally activated curing in the absence of any catalyst forming polyacetylene thermoset with high thermal stability. (c) 2008 Elsevier Ltd. All rights reserved.