Synthesis and characterization of poly(propylene sulfite) from sulfur dioxide and propylene oxide using zinc derivatives as catalysts

The zinc glutarate catalyzed copolymerization of sulfur dioxide (SO₂) and propylene oxide (PO) was investigated in detail by varying temperature, time, monomer feed ratio, and PO feed per catalyst as well as by using solvents, such as PO and chloroform. An optimized copolymerization [PO]/[catalyst] = 300, and no solvent at 60°C, 40 h, [PO]/[SO₂] = 1, resulted in poly(propylene sulfite) (PPS) with high molecular weight I_n = 42 000 (I_w /I_n = 2.1) never achieved before. PPS was obtained in a yield of 66.9 g per g of catalyst (namely, 12.93 kg per mol of catalyst) and determined to consist of 90.4 mol‐% sulfite‐linkage and 9.6 mol‐% ether‐linkage. A polymer containing a large amount of ether‐linkages was additionally formed as a minor component. However, no formation of cyclic propylene sulfite as byproduct was detected. In addition, zinc hexacyanoferrate(III) was prepared and used in the copolymerization as a catalyst, but showed almost no catalytic activity.