Elaboration of Biobased Nonisocyanate Polyurea Materials with Shape-Memory Properties

Thermosetting biobased shape-memory materials that exhibit both shape memory effect and the ability to permanently reconfigure their shape have been prepared. These materials were composed of a synthesized nonisocyanate biobased amino-terminated polyurea (NIPUrea), a biobased multiepoxy cross-linking agent, and 4,4'-diaminodiphenyl disulfide (DADS) as a source of disulfide dynamic bonds that promote the topological rearrangement of the cross-linked network structure through thermal stimulation. DADS-based materials exhibited increasing values of Tg and Tα with DADS content, ranging from 9 to 34 °C and from 30 to 58 °C, respectively. They exhibited good thermal stability up to around 270 °C. They also displayed good mechanical properties, with Young's Modulus values increasing with the DADS content from 15 to 310 MPa. Controls with similar chemical structures but without disulfide bonds, based on 4,4′-methylenedianiline (MDA), were also prepared and exhibited thermo-mechanical properties close to those of DADS-based materials. Materials prepared with a ratio DADS (or MDA)/NIPUrea of 1/1 or 2/1 showed shape memory properties of the initial shape at room temperature and also shape reconfiguration at high temperature. However, only the material DADS 2/1, with the highest disulfide bond content, was able to effectively recover the reconfigured permanent shape at room temperature.