Abstract
A series of substituted acetylenes has been polymerized with WOCl~4~/Ph~4~Sn metathesis catalyst and [Rh(cod)OMe]~2~ insertion catalyst, and the thermal degradation of the polyacetylenes prepared has been studied using pyrolysis capillary gas chromatography (Py‐GC) with flame ionization and mass spectrometric detection to obtain information on the effect of the catalyst on the head‐tail (H‐T) isomerism of polyacetylenes (poly(phenylacetylene), poly[(4‐methylphenyl)acetylene], poly(benzylacetylene), poly[(2‐fluorophenyl)acetylene], poly[(3‐fluorophenyl)acetylene], and poly[(4‐fluorophenyl)acetylene]). Cyclotrimers have been found to be the main pyrolysis products in all cases. Direct Py‐MS connection was used to determine the temperature profiles of the released pyrolysis products. 1,3,5‐Trisubstituted benzenes were found to be the predominant pyrolysis products of the polymers prepared with the insertion catalyst, which proves the presence of long head‐to‐tail sequences of monomeric units in these polyacetylenes. On the other hand, both 1,2,4‐ and 1,3,5‐trisubstituted benzenes are present in significant amounts in the pyrolysis products of polymers prepared with the metathesis catalyst, which proves the presence of a significant content of the head‐to‐head (HH) and tail‐to‐tail (TT) linkages in these isomers of polyacetylenes. Contents of the regular (HT) and inverse (HH‐TT) monomer linkages (RML and IML, respectively) in polymer chains were determined from the relative amounts of di‐, tri‐, and tetrasubstituted benzenes found in the Py‐GC products.