Synthesis, Dynamic Mechanical Properties, and Shape Memory Effect of Poly(benzoxazine-ether-urethane)s

Two series of poly(benzoxazine-ether-urethane)s (PBEUs) are prepared through thermally activated ring-opening polymerization (ROP) of bi-functional benzoxazines containing ether-urethane moieties. The bi-functional benzoxazines are synthesized through coupling reaction of hydroxyl-containing mono-functional monomers based on phenol, o-allylphenol, o-cresol, p-cresol, diglycolamine, and paraformaldehyde with 1,6-hexamethylene diisocyanate (HDI) and 2,4-toluene diisocyanate (TDI), respectively. The ROP temperature of each HDI-based benzoxazine is higher than that of the counterpart based on TDI, and they are in descending order ortho-, para-, and unsubstituted phenol for both series. Due to the difference in structure symmetry between the two series monomers, the variation of polymerization rate with temperature of each TDI-based benzoxazine is different from that of the counterpart based on HDI. The ortho- and para-substituted-phenol-based PBEUs show lower glass transition temperatures than that of the phenol-based counterpart. In the vicinity of the glass transition temperature, the HDI-based PBEUs exhibit thermally induced one-way dual-shape memory effect.