Bulk CO2-based Amorphous Triols Used for Designing Biocompatible Shape-Memory Polyurethanes
Precursors with sharp crystalline transition temperature have attracted significant attention in the field of shape-memory materials; however, seldom have reports been related to amorphous ones with industrial application prospects. This study introduced a new family of amorphous CO2-based hydroxyl-telechelic three-armed oligo(carbonate-ether) triol (Triol) with controllable molecular weight (Mn) and carbonate unit content (CU), which was coupled with PEG and 1,6-hexamethylene diisocyanate (HDI) to afford crosslinked polyurethanes (PU) networks with well-defined architecture. A crosslinking point was provided by Triol and PEG was used to afford networks some crystallinity. The resulting networks were characterized using attentuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and differential scanning calorimetry (DSC), and the shape-memory effect test provided insight into the relationship between shape memory behaviors and polymeric structures. The networks displayed good dual-shape memory effect when compared with others: shape fixity ratio (R f) could be controlled by changing the Triol content and Mn, and all the shape recovery ratios (R r) of the networks could unexpectedly approach 100% under the experimental conditions. Interestingly, the substructure of the Triol CU, could effectively regulate the recovery time of the networks, e.g., the recovery time decreased with the increment of Triol CU without changing Rf and Rr. Besides, crystalline transition temperature could be simply changed by altering Triol content. A typical sample Triol(2k, 50%)40-PEG(6k)60 displayed excellent dual-shape effect with almost 100% Rf and Rr at a recovery time of 40 s at 70°C. More interestingly, this sample could almost immediately recover its original shape (in less than 3 s) when immersed in 70°C water. Direct contact and MTT tests were used for assessment of cell viability and proliferation. These results confirmed the potential of these polyurethanes as a new family of tunable biomedical shape-memory materials.
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