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Shape-memory polymers with supramolecular switch have received increasing attention. This study reports the synthesis and characterization of supramolecular shape-memory polyurethane based on Cu(II)–pyridine coordination, obtained by mixing pyridine containing polyurethane with CuCl2. The results show that there are strong metal–ligand coordination interactions formed between Cu(II) and the pyridine ring in a series of CuCl2-doped polyurethane samples. The Cu(II)–pyridine coordination plays a crucial role in the enhanced physical netpoints for outstanding shape-memory properties. Indeed, the so-synthesized CuCl2-doped polyurethane exhibits not only a rapid tensile shape recovery but also excellent crimp shape recovery. The CuCl2-doped polyurethane containing suitable metal–ligand coordination interactions shows more than 99% shape fixation and more than 95% shape recovery. Our findings promote further applications of shape-memory polymers in multiple engineering fields.

In this study, a series of novel shape memory polyurethanes (SMPUs) containing tertiary amine groups are prepared by designing hexamethylene diisocyanate (HDI)–N-methyldiethanolamine (MDEA) as soft segments and HDI-BDO as hard segments. The structure and properties of the MDEA-based SMPUs are investigated using FT-IR, NMR, DSC, TGA, DMA, POM and AFM. The results demonstrate that the MDEA-based SMPU is composed of an amorphous soft phase and hard phase. The hard phase is amorphous below 20 wt% hard segment content (HSC), whereas the HDI-BDO segments form a semi-crystalline hard phase above 30 wt% HSC. This morphology exhibits good thermally induced SMEs with 100 % shape fixity and more than 80 % shape recovery. Moreover, the MDEA-based polyurethanes are expected to be further multifunctionalized for antibacterial activity, biocompatibility, multi-responsiveness and many other properties. This work provides a new strategy for designing multifunctional shape memory polymers with amine-containing polyurethanes.

Supramolecular polymers are attractive in recent years. In this article, a series of pyridine containing polyurethanes (PUPys) with various pyridine contents and various MDI-BDO contents were synthesized from 1,6-hexamethylene diisocyanate (HDI), 1,4-butanediol (BDO), N,N-bis(2-hydroxylethyl) isonicotinamine (BINA) and diphenylmethane diisocyanate (MDI). Thereafter, the moisture absorption of PUPys was mainly investigated systematically from the effect of temperature, relative humidity (RH), pyridine content, MDI-BDO content, the mechanism, and the kinetic of moisture absorption. Results show that the moisture absorption process of PUPys matches with Fick’s second law in the initial stage. The moisture absorption is dependent on the content of N,N-bis(2-hydroxylethyl) isonicotinamine (BINA), e.g., the moisture absorption decreases with the increase of MDI-BDO content as well as the decrease of BINA content. In addition, the moisture absorption increases with the increase of temperature and relative humidity (RH). Accordingly, the moisture absorption process of PUPy45 at RH = 65% and T = 25° can be expressed with the equation: lnMt = 8.88–2975(1/T) + 0.5lnt. On the basis of the moisture absorption, the shape recovery process of PUPys film under the moisture condition support that PUPys show excellent moisture-responsive shape memory effects.

Shape memory polymers are attractive for both science and industrial application. In this article, a series of pyridine-containing supramolecular shape memory polyurethanes (Py-SMPUs) with various diphenylmethane diisocyanate–butanediol (MDI–BDO) contents are synthesized from the 1,6-hexamethylene diisocyanate (HDI), N,N-bis(2-hydroxylethyl) isonicotinamide (BINA), BDO, and MDI. Then, they are investigated systematically using FT-IR, DSC, DMA, WAXD, and shape memory testing. The results show that the addition of MDI–BDO segment improves the strength of hydrogen bonding of Py-SMPUs. It promotes the formation of hard domains, but not influences the phase-separation structure, the intensity, and distribution of physical netpoints. In addition, the MDI–BDO segment improves the rubber modulus and drops the energy loss of Py-SMPUs. However, it does not influence the shape memory behaviors which are mainly influenced by the BINA content. If the BINA content is beyond 30 wt%, good shape memory effect can be achieved in the BINA–HDI–BDO–MDI system; and high shape recovery force can be obtained by increasing the MDI–BDO segment.

Thermal properties of polymer are very important to the understanding of morphology and shape memory effect of shape memory polymers (SMPs). In this article, the thermal properties of shape memory polyurethane nanofibrous nonwoven are investigated systematically from the morphology of nanofibers, crystalline structure, isothermal crystallization behavior, and thermal-dependent strain recovery. The results indicate that the thermal properties of shape memory polyurethane nanofibrous nonwoven are influenced greatly by the electro-spinning and the recrystalline condition. The crystal melting temperature (T m) decreases as the crystallization temperature (T c) decreases, while the relative degree of crystallinity (X c) increases with the decrease of T c within the temperature range of 20 to −30 °C. In particular, when the annealing temperature is higher than 150 °C, the T m shifts to higher value and the X c decreases significantly with the increase of T c. Finally, temperature-dependent strain recovery curves show that the shape memory polyurethane nanofiber tends to have a lower recovery temperature as compared with the SMPU bulk film due to their ultrafine diameter.