A Nonisocyanate Strategy toward Polyurethane Vitrimers from Alkylene Bisurea and Epoxide through Eutectic-Assisted Melting
Nonisocyanate polyurethanes (NIPUs) are nowadays considered as green alternatives to conventional polyurethanes, without using the toxic isocyanates. NIPUs usually are synthesized from cyclic carbonates and di(poly)amines. Herein a novel pathway toward polyurethane vitrimers (PUVs) based on epoxide (1,4-butanediol diglycidyl ether, BDE) and alkylene bisureas (BUs) is reported, which can easily be prepared from renewable urea and diamines. Due to the high melting temperature and the poor solubility, BUs are rarely applied in the synthesis of polyurethanes. To enhance the mellability of BUs, ZnCl 2 is introduced to form eutectic system and therefore to assist melting of BUs (eutectic-assisted melting). When 100 mol% of ZnCl 2 is added, BUs are able to melt at 130 °C at which polymerization between BUs and BDE is then triggered and can be finished within 10 min. Interestingly, the obtained polymers are found to be polyurethane vitrimers, for which the relationship between the relaxation time ( τ *) and the temperature ( T ) fits with Arrhenius equation. PUV-10 samples before and after reprocessing remains similar appearance and mechanical properties ( E : ≈90 MPa; σ b : ≈17 MPa; ε b : ≈200%). A new synthetic strategy is apparently offered here for NIPUs and even for PUVs without adding any crosslinker.
危险品化学品经营许可证（带存储）