Initiation of free-radical polymerization of acetylene monomers with molecular chlorine at low temperatures

The reactions of molecular chlorine with phenylacetylene (PA) and para-diethinylbenzene (p-DEB) at low temperatures (77–210 K) were studied by electronic paramagnetic resonance (EPR), size exclusion chromatography, double bond analysis (DBA), calorimetry, and UV, visible, and IR spectroscopy. The low-temperature (100–210 K) reactions of molecular chlorine without high-energy chemical (HEC) effects formed radicals capable of oligomerizations and polymerizations. A readily soluble polymer para-diethinylbenzene having no spatial cross-linkages (but possibly having a branched structure) was obtained. Polymerization occurred in direct contact with chlorine. It accelerated near the melting point (Tm) of chlorine and proceeded vigorously along with chlorination at Tm = 172 K. The occurrence of low-temperature polymerization without HEC treatment points to the high reactivity of the reagents. From the viewpoint of applications, low-temperature oligomerization or polymerization of monomers with molecular chlorine can afford oligomers or polymers with definite properties, which cannot be obtained by other initiation procedures.