Synthesis of Aliphatic Carbonate Macrodiols and Their Application as Sustainable Feedstock for Polyurethane

High-molecular-weight poly(propylene carbonate) (PPC) [number-average molecular mass (M _n): 80 000-100 000] is readily alcoholized into PPC macrodiols in the presence of 1,2-propanediol (PDO), 1,4-butanediol (BDO), or 1,6-hexanediol (HDO). The high-molecular-weight PPC and small amount of diols, such as PDO, BDO, or HDO, were stirred at elevated temperatures to convert the extremely viscous high-molecular-weight polymer to low-molecular-weight macrodiols with gel permeation chromatography-measured M _n of about 3000 Da. The chopping reaction of the high-molecular-weight PPC was studied in detail, such as the influences of the catalyst residue, the kinds of alcoholysis agents, reaction temperature, and time. The reaction mechanism of alcoholysis is proposed according to the experimental results. The results indicate that the presence of a trace residue of zinc catalyst (Zn-G-III) in PPC, excess diol feeding, and higher temperature can accelerate the alcoholysis. Moreover, different diols can produce different PPC macrodiols with varying end-capping. Finally, polycarbonate ether urethane can be successfully synthesized using as-synthesized PPC macrodiols and poly(propylene glycol) (M _n ≈ 3000) as the soft segment and 4,4'-diphenylmethane diisocyanate or BDO as the hard segment. The full evaluation for the synthesized PPC macrodiols demonstrates their potential applications in the polyurethane industry.