Organic-inorganic polyureas with benzyl hindered urea bonds and POSS cages in the main chains: Synthesis, shape memory and reprocessing properties

Abstract

The organic–inorganic polyureas with benzyl hindered urea bonds (HUBs) and POSS cages as the main-chain structural units were synthesized via the polyaddition of 4,4′-diphenylmethane diisocyanate with α,ω-dibenzyl diamines including α,ω-dibenzylamino-terminated poly(ethylene oxide), N,N’-dibenzylhexamethylene-1,6-diamine and 3,13-dibenzylaminoanilino double decker silsesquioxane. The organic–inorganic PUreas were microphase-separated, in which the POSS cages were self-assembled into the microdomains via POSS-POSS interactions. The POSS microdomains acted as the physical crosslinking points and thus the organic–inorganic PUreas behaved as the crosslinked elastomers; the physical crosslinking remained thermally stable even at elevated temperature as high as 200 °C. In spite of the high thermal stability, the networks can be reprocessed with the plasticity in solids via the dynamic exchange of benzyl HUBs. Due also to the physical crosslinking, the organic–inorganic PUreas possessed the excellent shape memory properties; the original shapes were re-configurable by taking advantage of the benzyl HUBs in the main chains.