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Polyurethane by Ionic Liquid Crosslink; A New Class of Super Shape-Memory Like Polymer


This investigation reports on the synthesis of a new class of ionic liquid crosslinked shape-memory polyurethane (PU-IL) based on polycaprolactone diol and 4,4′-methylenebis(phenyl isocyanate) (MDI), which can overcome the major drawbacks of conventional shape-memory polyurethanes. In this case, the ionic liquid crosslinker in PU-IL exhibited not only the higher shape-recovery ratio (98%), but also showed excellent shape-fixity (98%). In the second cycle of the cyclic tensile test, PU-IL showed almost complete shape recovery while maintaining excellent shape fixity. The higher shape-fixity value in PU-IL was also supported by its higher crystallization and melting enthalpy, as evidenced by the DSC analysis. The properties of this PU-IL were compared with those of conventional linear PU having 1,4 butanediol (BDO) as chain extender as well as of non-ionic crosslinked PU using trimethylolpropane (TMP). Ionic liquid as crosslinker reduced the glass transition temperature (Tg), whereas the non-ionic crosslinker increased the Tg. Interestingly, the soft segment crystallinity as well as melting enthalpy of PU-IL is higher than that of PU-BDO, whereas no melting or crystallization peak was observed in the DSC thermograms of PU-TMP. The DSC results were supported by the DMA analysis. The higher Tg and the absence of soft domain melting transition indicated complete intermixing of hard and soft phases in PU-TMP, but the ionic interaction in PU-IL restricted this. The inter-domain mixing in PU-TMP was also supported by the absence of a scattering peak in SAXS analysis. FT-IR spectroscopy showed the stronger hydrogen bonding in PU-BDO followed by PU-TMP and PU-IL.

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Publication details

The article was received on 10 Apr 2018, accepted on 11 Jun 2018 and first published on 12 Jun 2018

Article type: Paper
DOI: 10.1039/C8PY00549D
Citation: Polym. Chem., 2018, Accepted Manuscript
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    Polyurethane by Ionic Liquid Crosslink; A New Class of Super Shape-Memory Like Polymer

    P. K. Behera, P. Mondal and N. K. Singha, Polym. Chem., 2018, Accepted Manuscript , DOI: 10.1039/C8PY00549D

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