Sulfide bond formation for the synthesis of poly(thioarylene) through oxidation of sulfur chloride with aromatics

A new homogeneous series of hydrocarbon polymers having phenoxy and thiophenoxy units in the main chain were prepared by oxidative polymerization of α,ω-diphenoxyalkanes (m = 2-8, 10) with S₂Cl₂. Polymers with weight-average molecular weights in the range of 4800-33 500 have been obtained in high yields (>94%). The effect of the chain length of the methylene units on the thermal properties of the polymers is discussed. Increasing the length of the methylene units results in a decrease in the glass transition temperature (T_g) of the polymers. An alternating odd-even effect in melting temperatures (T_m) and molecular weights is observed. The resulting polymers having even numbers of methylene units possess a higher melting temperature and lower molecular weight than those of the odd numbered ones. Polymerization of S₂Cl₂ with other aromatic compounds, such as p-xylene, durene, and diphenyl ether, is also demonstrated to yield the corresponding poly(thioarylene)s. The polymerization proceeds via a cationic mechanism through the oxidation of the disulfide bond.