Randomly copolymerized poly(carbonate) glycols were employed as starting materials for the synthesis of polyurethane elastomers (PUEs). The poly(carbonate) glycols had hexamethylene (C 6 ) and tetramethylene (C 4 ) units between carbonate groups in various composition ratios (C 4 /C 6 ϭ 0/100, 50/50, 70/30, and 90/10), and the number-average molecular weights of these poly(carbonate) glycols were 1000 and 2000. The PUEs were synthesized with these poly(carbonate) glycols, 4,4Ј-diphenylmethane diisocyanate, and 1,4-butanediol by a prepolymer method. Differential scanning calorimetry measurements revealed that the difference between the glass-transition temperature of the soft segment in the PUEs and the glass-transition temperature of the original glycol polymer decreased and the melting point of the hard-segment domain increased with an increasing C 4 composition ratio. The microphase separation of the poly(carbonate) glycol-based PUEs likely became stronger with an increasing C 4 composition ratio. Young's modulus of these PUEs increased with an increasing C 4 composition ratio. This was due to increases in the degree of microphase separation and stiffness of the soft segment with an increase in the C 4 composition ratio. The molecular weight of poly(carbonate) glycol also influenced the microphase-separated structure and mechanical properties of the PUEs. The addition of different methylene chain units to poly(carbonate) glycol was quite effective in controlling the microphase-separated structure and mechanical properties of the PUEs.

Mechanical properties of thermoplastic polyurethane elastomers based on either polyether or polycarbonate (PC)-glycols, 4,4’-dipheylmethane diisocyanate (1,1’-methylenebis(4-isocyanatobenzene)), 1,4-butanediol, were controlled by restriction of crystallization of polymer glycols. For the polyether glycol based-polyurethane elastomers (PUEs), poly(oxytetramethylene) glycol (PTMG), and PTMG incorporating dimethyl groups (PTG-X) and methyl side groups (PTG-L) were employed as a polymer glycol. For the PC-glycol, the randomly copolymerized PC-glycols with hexamethylene (C6) and tetramethylene (C4) units between carbonate groups with various composition ratios (C4/C6 = 0/100, 50/50, 70/30 and 90/10) were employed. The degree of microphase separation and mechanical properties of both the PUEs were investigated using differential scanning calorimetry, dynamic viscoelastic property measurements and tensile testing. Mechanical properties could be controlled by changing the molar ratio of two different monomer components.