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

Abstract

Alcoholysis of bisureas (BUs) would be of great potential among the non-isocyanate routes for preparing polyurethanes, if the issue of the high melting temperature and the poor solubility for BUs can be solved. In this study, it is proposed to introduce Li salt to assist the melting of BUs via a eutectic system. It is found that the melting point of BUs indeed can be reduced to 170 °C or even lower by adding 40 mol% of LiCl or LiBr. In the polymerizations of BUs with diols, it is found that ZnO nanoparticles (30 ± 10 nm) are the most efficient catalyst in the catalyst screening study. Four polyurethanes are successfully synthesized and the glass transition temperature of them is detected to be 34-45 °C. PU1010 is tougher than other polymers so that it is able to be molded. The Young's modulus of PU1010 is 195.1 MPa, while the strength and the elongation at break are 36.4 MPa and 280%, respectively. The toughness calculated is 67.3 J cm −3 . This Li salt-assisted melting strategy not only realizes the synthesis of polyurethanes through alcoholysis of BUs, but can also be extended to the synthesis of other high performance polymers.

Understanding of ZnO‐Catalyzed Polyurethane Synthesis from Bisurea for Further Exploration of One‐Pot Synthesis and Property Evaluation Thereof

“…[27,28] ZnO can also be used as a catalyst to promote the ring-opening polymerization of lactide and even the polymerization of methyl methacrylate. [29][30][31] In our previous study, [32] it has been confirmed that it is feasible to synthesize NIPUs via polycondensation of bisureas (BUs) with diols, and ZnO has been found as the most efficient catalyst for the alcoholysis of BUs in the formation of NIPUs. BUs can be obtained simply from urea and diamines.…”

“…The formation of PUs was performed under the catalysis of Zn(NCO) 2 (NH 3 ) 2 at 170 °C, and 40 mol% lithium bromide (LiBr) was added to the melting of 1,10-decylene bisurea (DBU) (the obtained polymers are denoted as PU-Zn-x, where x represents the loading of Zn(NCO) 2 (NH 3 ) 2 relative to DBU). In our previous work, [32] 40 h is needed to finalize PU with a sufficient molecular weight when catalyzed by 5 mol% ZnO (30 ± 10 nm). Using Zn(NCO) 2 (NH 3 ) 2 as the catalyst under the same conditions, it is found that the reaction time can be reduced to 26 h (see Table 1, PU-Zn-5).…”

“…This result is consistent with the ZnO loading in our previous study. [32] It is worth to note that when the loading of Zn(NCO) 2 (NH 3 ) 2 is increased further, some part of the catalyst cannot dissolve in the reaction system and as a result, the system is not transparent. The limited solubility of Zn(NCO) 2 (NH 3 ) 2 in the system should be taken into account.…”

Flame retarded polyurethane vitrimers containing isocyanurate rings: Synthesis and properties

“…23 The two peaks at 2945 and 2860 cm À1 correspond to the asymmetrical and symmetrical C-H stretching of the aliphatic methylene group while the signal at 1546 cm À1 correspond to the C-N stretching of urethane group. 51 The peak at 1462 cm À1 is the signal of the C-N stretching signal of the isocyanurate group. 23 For VPICU4-3/2 and VPICU6-3/2, the peaks at 1462 cm À1 are much sharper, which is understandable due to the increased content of isocyanurate segment.…”