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

Abstract

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 α,ω-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 reactions 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 nanostructures, 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.