Add time:07/31/2019         Source:sciencedirect.com

AA-BB and AB-type Non-Isocyanate Polyurethanes (NIPUs) were synthesized through a cross metathesis polymerization between methyl carbamate and methyl carbonate groups within AA-BB and AB monomers. These monomers were prepared by reaction of diamines, diols or amino-alcohols with an excess of dimethylcarbonate (DMC), using 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as catalyst. Due to a slight chain extension, dimethyl dicarbonate monomers as well as AB-type monomers contained few carbonate groups, which were present within the final NIPUs. The polymerization was performed in bulk at 200 °C, using K2CO3 as catalyst. Except for AB-type monomers obtained from amino-alcohols with 3 and 4 methylene groups, the polymerization was successful leading selectively to the expected NIPUs. These materials exhibited good thermal properties with Tg ranging from −35 to 10 °C, Tm ranging from 96 to 256 °C and degradation temperature above 200 °C. The polyurethane properties were generally intermediate comparing to those of polyurea and polycarbonate analogues prepared in the same conditions.

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