Concerning the occurrence of in‐stent restenosis and stent thrombosis of stent implantation with balloon angioplasty, a dual‐induced self‐expandable stent based on biodegradable shape memory polyurethane nanocomposites (PCLAU/Fe3O4) was developed. The stent could maintain its temporary shape at body temperature for a certain period of time while it was able to recover to its permanent shape at the temperature a little above body temperature (around 40 °C) in both a water bath and an alternating magnetic field. The trigger temperature and remote local heating ensured enough operation time and harmless activation without heating the body tissue. The nanocomposites had high fixing ratios above 99% and recovery ratios above 82% at both 37 and 40 °C. Cytotoxicity and in vitro degradation showed the nanocomposites had good biocompatibility and biodegradability. The PCLAU/Fe3O4 nanocomposites with dual‐responsive shape memory effects, desirable mechanical properties, biocompatibility, and biodegradability show great potential for vascular stents. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45686.

Polylactide-based polyurethane shape memory nanocomposites (Fe 3 O 4 /PLAUs) with fast magnetic responsiveness are presented. For the purpose of fast response and homogeneous dispersion of magnetic nanoparticles, oleic acid was used to improve the dispersibility of Fe 3 O 4 nanoparticles in apolymer matrix. A homogeneous distribution of Fe 3 O 4 nanoparticles in the polymer matrix was obtained fornanocomposites with low Fe 3 O 4 loading content. A smallagglomeration was observed fornanocomposites with 6 wt% and 9 wt% loading content, leading to a smalldecline in themechanical properties. PLAU and its nanocomposites have glass transition around 52 °C, which can be used as the triggering temperature. PLAU and its nanocomposites have shape fixity ratios above 99%, shape recovery ratios above 82% for the first cycle and shape recovery ratios above 91% for the second cycle. PLAU and its nanocomposites alsoexhibit a fast water bath or magnetic responsiveness. The magnetic recovery time decreases with anincrease inthe loading content of Fe 3 O 4 nanoparticles due to animprovement in heating performance for increased weight percentage of fillers. The nanocomposites have fast responses in an alternating magnetic field and have potential applicationin biomedical areas such as intravascular stent.

A series of random copolymers (PCLAs) were synthesized by ring-opening polymerization of D,L-lactide (LA) and ε-caprolactone (CL) with different molar ratios. PCLA based polyurethanes (PCLAUs) were obtained by chain-extending of PCLA and polytetramethylene ether (PTMEG) with hexamethylene diisocyanate (HDI). All the PCLAUs exhibit good shape memory properties with high shape fixity ratios above 98% and shape recovery ratios above 82% in the first cycle and 91% in the second cycle. PCLAUs with less CL content show faster recovery speed and PCLAUs with more CL content show higher shape recovery ratio. The trigger temperature can be tuned or controlled around body temperature by adjusting the molar ratio of LA to CL. The PCLAUs have potential applications in implant biomedical devices, especially for minimally invasive deployable devices.

Ester-based polyurethane (PU) was found to have excellent shape memory properties with low trigger temperature. Polyhedral oligomeric silsesquioxanes (POSS) have drawn considerable interest due to their hybrid organic-inorganic structures consisting of a silica cage surrounded by eight organic groups. Incorporation of functional POSS in polymers normally improves the mechanical properties of polymer matrix. For the purpose of obtaining shape memory materials with low trigger temperature and quick response, octa(3-hydroxypropyl) polyhedral oligomeric silsesquioxane (POSS-(OH) 8 ) was incorporated into polyurethane by solution casting. The chemical structures and microstructures were characterized by Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD) and field emission scanning electron microscope (FESEM). The thermal properties and dynamic mechanical properties were investigated by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The mechanical properties were also evaluated. Shape memory properties were characterized by cyclic thermal mechanical tests and physical shape recovery tests. The results show that the nanocomposites with low POSS-(OH) 8 loading content (1 and 3 wt.%) possess higher breaking strength and elastic modulus, resulting in higher shape fixity, recovery ratios and faster recovery. The nanocomposites might have potential applications for controlling tags or proof marks in the area of low temperature storage.