Patent Title: DYNAMIC UREA BONDS FOR POLYMERS
Number/Link: W02016/069582
Applicant/Assignee: University of Illinois
Publication date: 6-05-2016
“Gist”: Urea bonds prepared from sterically hindered amines and isocyanates
Why it is interesting: The N-C bond in urea is very stable due to conjugation of the lone electron pair of the nitrogen atom with the cabonyl group. According to this invention, the nitrogen atom can be subsituted with a strongly hindering group such that the coplanarity, and therefore most of the conjugation, of the C-N and C=O bonds is lost. These hindered urea bonds are much less stable and can reversibly depolymerize at relatively low temperatures. Thermoreversible bonds can be useful in a number of smart materials such as self-healing-, “4D printing”- , and reprogrammable shape memory materials. In an example a shape memory material with a Tg of 53°C and a Young’s Modulus of about 2 GPa was prepared by reacting 2-(t-buylamino)ethanol (TBAE) and trimerized hexamethylene diisocyanate (THDI). The ‘permanent shape’ of the material could be re-programmed by forcing the material in a new shape for 72 hours at 60°C.
Poly(urethane-urea) with thermoreverisble urea bonds
Innovation in Polyurethanes 