Enhanced mechanical and oxygen barrier performance in biodegradable polyurethanes by incorporating cellulose nanocrystals with interfacial polylactide stereocomplexation
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Using bio-derived cellulose nanocrystals (CNCs) to reinforce the mechanical properties of biodegradable polyurethanes (PUs) is a promising approach especially when attempting to fabricate fully sustainable materials with high performance. However, the way to efficiently improve the dispersion and interfacial strength of CNCs in PU matrices is still an open question. In the current work, poly-l-lactide (PlLA) grafted CNCs (CNC-g-l) and a PU elastomer with poly-d-lactide as partial soft segments (d-PU) were first prepared separately, and then the fully biodegradable PU nanocomposites were fabricated by solution blending of CNC-g-l and d-PU. The surface grafting of PlLA can improve the thermal stability of CNCs, but has marginal effect on that of the nanocomposites. The improved dispersion of CNCs and enhanced interfacial strength, as evidenced by scanning electron microscopy, wide-angle X-ray diffraction and rheology measurements, are achieved by the construction of interfacial polylactide stereocomplexation (sc-PLA). The optimal improvement in mechanical properties of the nanocomposites is realized when only 1 wt% CNC-g-l is incorporated in the d-PU matrix. With the assistance of interfacial sc-PLA, the nanocomposite can gain 40% reduction in oxygen transmission rate at the optimal CNC-g-l content of 5 wt%. This study may provide a new method to improve the dispersion and interfacial strength of CNCs in biodegradable PUs and achieve simultaneously mechanical and barrier performance enhancement.
KeywordsBiodegradable Polyurethane elastomer Cellulose nanocrystal Interfacial strength Stereocomplexation
This work was financially supported by the National Science Foundation of China with Grant Nos. 51503055, 51673056 and the Provincial Science Foundation of Anhui with Grant No. 1608085ME88 and the National Key Research and Development Program of China with Grant No. 2017YFB0903803.
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Conflict of interest
The authors declare that they have no conflict of interest.