Poly(thiocarbonate) Synthesis from Carbonyl Sulfide (or Carbon Disulfide), Diol, and Dichlorides: A Step Growth Route to PE-like Sulfur-containing Polymers

The facile synthesis of high-valued polymers from waste molecules or low-cost common chemicals presents a significant challenge. Here, we develop a series of degradable poly(thiocarbonate)s from the new step-growth polymerization of diols, carbonyl sulfide (COS, or carbon disulfide, CS₂), and dichlorides. Diols and dichlorides are common chemicals, and COS (CS₂) is released as industrial waste. In addition to abundant feedstocks, the method is efficient and performed under mild conditions, using common organic bases as catalysts, and affording unprecedented polymers. When COS, diols, and dihalides were used as monomers, optimized conditions could completely suppress the oxygen-sulfur exchange reaction, enabling the efficient synthesis of well-defined poly(monothiocarbonate)s with melting points ranging from 48 °C to 101 °C. These polymers, which have a structure similar to polyethylene with low-density in-chain polar groups, exhibit remarkable toughness and ductility that rival those of high-density polyethylene (melting point: 90 °C, tensile strength: 21.6±0.7 MPa, and elongation at break: 576%). Moreover, the obtained poly(monothiocarbonate)s can be chemically degraded by alcoholysis to yield small-molecule diols and dithiols. When CS₂ was used in place of COS, a pronounced oxygen-sulfur exchange reaction occurred. By optimizing reaction condition, it was found that polymers with -S(C=O)S- and -S(C=S)S- as the main repeating units exhibited high thermal stability and crystallinity. Thus, a new approach for regulating the structure of polythiocarbonates via the oxygen-sulfur exchange reaction is developed. Overall, the polymers hold great potential for green materials due to their facile synthesis, readily available feedstocks, excellent performance, and chemical degradability.