Preparation and characterization of cross-linked polyurethanes using β-CD [3]PR as slide-ring cross-linker

To explore the toughening and damping potential of slide-ring (SR) structure as an energy dissipation unit, a β-cyclodextrin (CD) [3]polyrotaxane (β-CD [3]PR) was prepared via the self-assembly of β-CDs with polyethylene glycol (PEG) diamine 1,1′-disubstituted ferrocene as a site-complementary polymer axle followed by end-capping with N-(triphe-nylmethyl)glycine. Subsequently, it served as a SR cross-linker to cross-link PEG and poly- (1,6-hexanediol)carbonate (PC) diols in the presence of 4,4′-diisocyanato dicyclohexyl-methane (HMDI) to give polyurethanes (PUs). Similar to β-CD as a cross-linker, the β-CD [3]PR cross-linked PUs also held a low, but relatively higher sol fraction range of 0.50 w%-3.20 w%. As a semi-crystalline prepolymer, the β-CD and β-CD [3]PR cross-linked PEG PUs presented a typical crystalline polymer tensile stress-strain behavior, while the cross-linked PUs using PC as an amorphous polymer showcased a pseudo-J-shaped stress-strain curve. Compared to the β-CD cross-linked PUs, the β-CD [3]PR cross-linked ones exhibited remarkably higher swelling ratio, fracture energy and loss tangent values, indicating β-CD [3]PR as an energy dissipation unit enabling to toughen and damp a variety of polymer materials.