Structural Instability Origins in Polythiocarbonates: O/S Exchange Phenomenon and Stability Hierarchy

Polythiocarbonates (PTCs) represent a class of polymers derived from polycarbonates. While numerous synthetic methodologies have been reported, their practical applications remain unexplored. This study employs a one-pot bulk polymerization approach using propylene oxide (PO) and carbon disulfide (CS2) to synthesize polythiocarbonates, systematically investigating the effects of reaction temperature and duration on polymer properties. Results demonstrate that optimized reaction conditions fail to suppress O/S exchange, inevitably yielding polymers containing diverse thiocarbonate groups with varying stabilities. Consequently, we established the structural thermal stability hierarchy of thiocarbonate linkages: S(C═O)O > S(C═O)S > O(C═S)O > S(C═S)S > S(C═S)O. Density functional theory (DFT) calculations of bond dissociation energies (BDEs) corroborate this experimentally determined sequence. Our findings identify inherent structural instability as the fundamental barrier to polythiocarbonate applications, providing critical design principles for developing functionally stable PTCs.