Add time:07/30/2019         Source:sciencedirect.com

Non-isocyanate thermoplastic polyureas (NIPUreas) were synthesized using an original approach. Dimethyl dicarbamates (DC) were prepared as monomers, by the reaction of a diamine with an excess of dimethylcarbonate (DMC), in presence of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as catalyst. Then, self-polymerization of DC was performed through a methylcarbamate metathesis reaction, in presence of K2CO3 or TBD as catalysts. The reaction was conducted under neat conditions at 160 or 200 °C. NIPUrea analogues were also synthesized by melt transurethane polycondensation between DC and corresponding diamine, in presence of K2CO3 or TBD as catalyst at 160 °C. The thermal properties were dramatically dependent on the synthesis approach and operating conditions. The obtained NIPUreas displayed Tg values varying from −37 to 118 °C, Tm values varying from 95 to 289 °C, and thermal stabilities above 200 °C. The metathesis reaction with TBD has been found not effective. Using K2CO3 as catalyst, metathesis seems to afford higher molecular weight comparing to transurethanization.

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