Reprocessable polyhydroxyurethane networks crosslinked with trifunctional polyhedral oligomeric silsesquioxanes via Diels-Alder reaction

In this contribution, we reported the polyhydroxyurethane (PHU) networks crosslinked with trifunctional polyhedral oligomeric silsesquixanes (POSS) via Diels-Alder (D-A) reaction. First, a linear PHU was synthesized via the step-growth polymerization of a difunctional six-membered bicyclic carbonate (6BCC) with an & alpha;,& omega;-diamino-terminated polytetrahydrofuran (NH2-PTHF-NH2) as well as 2,5-diaminomethylfuran. Second, an incompletely-condensed POSS macromer carrying three maleimido groups was synthesized via the multiple re-actions involving silylation, Heck and imidization. The linear PHU was crosslinked with the POSS macromer via the D-A reaction of furyl groups in the main chain of PHU with maleimido groups of the POSS macromer. The morphological investigation showed that the PHU-POSS networks displayed the microphase-separated nano -structures, in which the POSS cages were self-assembled into the spherical aggregates with the diameter of 20-30 nm. Compared to the linear PHU, the PHU-POSS networks displayed the improved thermomechanical properties. Thanks to the introduction of D-A linkages, more importantly, the networks possessed the excellent recycling (or reprocessing) and reconfigurable shape memory properties.

Automated summary

In this study, polyhydroxyurethane (PHU) networks crosslinked with trifunctional polyhedral oligomeric silsesquixanes (POSS) via Diels-Alder (D-A) reaction were reported. The networks showed microphase-separated nano-structures with self-assembled spherical aggregates. The introduction of D-A linkages improved the thermomechanical properties and enabled excellent recycling and reconfigurable shape memory properties.