The thermal polymerization of arylacetylene compounds has been studied from a monofunctional model compound, 4-(hexyloxy)phenylacetylene I. I was synthesized and bulk polymerized under several experimental conditions. The reaction products were analysed by chromatography, spectroscopy and spectrometry techniques. The observed average polymerization degree is low. The lowest molecular weight compounds were isolated and identified : they are two naphthalenic dimers and three benzenic trimers. They represent 30wt% of the whole polymerization product. We have shown also that the thermal polymerization of I is temperature and time dependent and that a depolymerization process takes place at high temperature.