Synthesis and characterization of a series of poly(alkylene carbonate) macrodiols and the effect of their structure on the properties of polyurethanes

A series of polycarbonate and copolycarbonate macrodiols was prepared by using an ester interchange reaction with ethylene carbonate and diols such as 1,6-hexanediol, 1,10-decanediol, 2,2-diethyl-1,3-propanediol, 1,4-cyclohexanedimethanol, and 1,3-bis(4-hydroxybutyl)-1,1,3,3-tetramethyldisiloxane. The diols were chosen to prepare a series of macrodiols with different structural features including linear, branched, rigid, and flexible. The macrodiols were characterized by ¹H- and ¹³C-NMR spectroscopy and DSC. The commercial macrodiol based on 1,6-hexanediol exhibited a high level of crystallinity, while with the exception of 1,10-decanediol-based copolycarbonates all the others were completely amorphous. 1,10-Decanediol-based materials showed partial crystallinity under subambient conditions. A series of polyurethane elastomers with a constant hard segment percentage (40 wt %) was prepared using 4,4′-methylenediphenyl diisocyanate and 1,4-butanediol as the hard segment. Tensile test results and Shore hardness measurements demonstrated that polyurethanes based on polycarbonate macrodiols prepared from 1,3-bis(4-hydroxybutyl)-1,1,3,3-tetramethyldisiloxane had the lowest modulus and hardness of the series of polyurethanes. The remaining polyurethanes had high tensile strength with poor elasticity. The morphology of the polyurethanes, as determined by DSC analysis, varied from completely phase-mixed to well phase-separated structures. Polyurethanes based on macrodiols prepared from 1,3-bis(4-hydroxybutyl)-1,1,3,3-tetramethyldisiloxane showed good phase-separated morphology, with sharp hard segment melting endotherms and soft segment glass transitions close to that of the pure soft segment.