A Nonisocyanate Strategy toward Polyurethane Vitrimers from Alkylene Bisurea and Epoxide through Eutectic‐Assisted Melting

Abstract

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.

High‐Performance Vitrimeric Benzoxazines for Sustainable Advanced Materials: Design, Synthesis, and Applications

“…[28] Many epoxy vitrimers have since been reported, featuring excellent properties. Other reported vitrimers are based on polybutadienes, [78][79][80][81][82] polyurethanes, [83][84][85][86][87][88][89][90][91][92][93][94][95][96][97][98][99] polyhydroxyurethanes, [100,101] polyurethane urea, [102,103] polyesters, [104][105][106][107][108][109][110][111][112][113][114][115] polycarbonates, [116] and polyimides. [117,118] These materials have low-to-medium-tohigh glass transition temperatures, with polyimide vitrimer achieving T g of 274 °C and a 5% weight loss temperature of 429 °C.…”

Non‐Isocyanate Polyurethanes by Alcoholysis of Alkyl Bisurea with Li Salt‐Assisted Melting: Synthesis and Properties

“…BUs, including 1,10-decylene bisurea (DBU) and 1,6-hexylene bisurea (HBU), were obtained by ammonolysis of urea and diamine (1,10-decanediamine, DDA or 1,6-hexanediamine, HDA) (see Scheme 1a), according to the method described in our previous work. [27] PUs were synthesized by the alcoholysis of BUs. LiCl or LiBr was used to assist decreasing the melting temperature of BUs (the melting point of DBU and HBU are 196 and 211 °C, respectively [32] ).…”

“…For example, Gambino et al found that the melting temperature of urea can be decreased to 28-117 °C when mixing with alkali halide to form an eutectic system. [26] In our previous work, [27] ZnCl 2 has been utilized to effectively decrease the melting point of BUs, from 200 to 130 °C. However, ZnCl 2 is not a good eutectic pair in the alcoholysis of BUs since it prefers to catalyze the release of HNCO rather than NH 3 and as a result, it is difficult to obtain high performance PUs.…”

Fully Closed-Loop Recyclable Thermosetting Polythiourethane Microspheres and Their Application in Efficient Fabrication of Composites with Segregated Structures

“…The appearance of CANs provides new ideas to solve this problem . The reprocessability and recycling of CPU can be gifted by classic carbamate bonds, urea bonds, and novel dynamic piperazine–urea bonds. − Lei et al prepared a series of thermosetting polyurea elastomers (TPUEs) by using propylene oxide diamine and different diisocyanate monomers as raw materials . TPUEs can be recycled based on the dynamic urea bond and maintain remarkable mechanical properties and chemical stability after multiple rounds of recycling.…”