A recent study published a report on the synthesis of novel ionic liquid crosslinked shape memory polyurethanes.
The new ionic liquid crosslinked shape memory polyurethane (PU-IL) is based on polycaprolactone diol and 4,4-methylisocyanate (phenyl isocyanate) (MDI), which can overcome the main shortcomings of traditional shape memory polyurethane. In this case, the ionic liquid cross-linking agent in PU-IL not only exhibited a higher shape recovery rate (98%), but also exhibited excellent shape fixability (98%). The second in the cyclic tensile test. During the cycle, PU-IL showed almost complete recovery of shape recovery while maintaining excellent shape fixability. The higher shape fixability of PU-IL was confirmed by DSC thermal analysis (Differential Scanning Calorimeter). Its higher crystallinity and support of melting enthalpy.
Reduce the glass transition temperature
Performance of a novel ionic liquid crosslinked shape memory polyurethane (PU-IL) with conventional linear polyurethane (PU-BDO) using 1,4-butanediol (BDO) as a chain extender, and using trimethylolpropane (TMP) The performance of nonionic crosslinked polyurethane (PU-TMP) was compared. The ionic liquid as a crosslinker reduces the glass transition temperature (Tg), while the nonionic crosslinker increases the glass transition temperature (Tg). Interestingly, the soft segmental crystallinity and melting enthalpy of PU-IL are higher than the soft segmental crystallinity and melting enthalpy of PU-BDO, while no melting or crystallization peak is observed in the DSC thermogram of PU-TMP. .
Dynamic thermomechanical analysis (DMA) support
The analysis results of DSC thermal analysis are supported by dynamic mechanical analysis (DMA). Higher glass transition temperature (Tg), and there is no soft segment melting transition, indicating hard segment and soft in PU-TMP The segments are completely mixed, but the ionic interactions in PU-IL limit this.
The SAXS analysis showed that PU-TMP has no scattering peaks and supports the mixing of soft and hard segments. FT-IR spectroscopy shows that PU-BDO has strong hydrogen bonds, followed by PU-TMP and PU-IL.