Design of triple-shape memory polyurethane with photo-cross-linking of cinnamon groups

A triple-shape memory polyurethane (TSMPU) with poly(ε-caprolactone) -diols (PCL-diols) as the soft segments and diphenyl methane diisocyanate (MDI), N,N-bis (2-hydroxyethyl) cinnamamide (BHECA) as the hard segments was synthesized via simple photo-crosslinking of cinnamon groups irradiated under λ > 280 nm ultraviolet (UV) light. Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance ((1)H-NMR) and ultraviolet-visible absorption spectrum (UV-vis) confirmed the chemical structure of the material. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) results demonstrated that the photo-crosslinked polymer possessed two transition temperatures, one is due to the melting point of the soft segment PCL-diols, and the other is due to the glass transition temperature. All these contributed to the cross-linked structure of the hard segments and resulted in an excellent triple-shape memory effect. Alamar blue assay showed that the material has good non-cytotoxicity and can be potentially used in biomaterial devices.