Thermally-activated shape memory behaviour of bionanocomposites reinforced with cellulose nanocrystals
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Bionanocomposites with thermally-activated shape memory ability have been designed based on a synthesized poly(ester-urethane) matrix reinforced with both neat and functionalized cellulose nanocrystals. The functionalization of the cellulose nanocrystals was performed by grafting poly(l-lactic acid) (PLLA) chains onto their surface. The matrix has a block copolymer structure of two biodegradable and biocompatible polymers, poly(ε-caprolactone) (PCL) and PLLA. This research is focused on the effects of cellulose nanofillers on the thermally-activated shape memory response of the neat matrix confirming that the bionanocomposites are able to show shape memory effects at 35 °C, close to the human body temperature, making these materials good candidates for biomedical applications. Three thermo-mechanical cycles at 50 % of deformation were performed in order to check the thermally-activated shape memory ability of the bionanocomposites and to determine the shape memory parameters, namely the strain fixity (Rf), and the strain recovery (Rr) ratio. Both bionanocomposites, with neat and functionalized cellulose nanocrystals, present excellent shape memory behaviour maintaining the recovery behaviour at values of about 90 % as measured previously for the pure matrix, indicating that the addition of the nanofiller maintains the good ability to recover the initial shape of the matrix. The cellulose nanofillers clearly improve the ability of the polymer to fix the temporary shape. In fact, the bionanocomposites show Rf at about 90 %. Moreover, bionanocomposites reinforced with the functionalized cellulose nanocrystals maintain constant their performance during all the thermo-mechanical cycles thus confirming that the improvement in the shape memory behaviour can be mainly attributed to the increase of the interactions between the functionalized cellulose nanocrystals with the polymeric matrix.
KeywordsPoly(l-lactic acid) Poly(ε-caprolactone) Bionanocomposites Thermally-activated shape memory behaviour Cellulose nanocrystals
We are indebted to the Spanish Ministry of Economy and Competitiveness (MINECO) for their economic support of this research (MAT2013-48059-C2-1-R). LP acknowledges also, the support of a JAEdoc Grant from CSIC cofinanced by FSE. We thank the technical support of Marco Rallini and Franco Dominici from the STM group of the University of Perugia for SEM photographs and microextruder blending, respectively.
- Huang WM, Zhao Y, Wang CC, Ding Z, Purnawali H, Tang C, Zhang JL (2012) Thermo/chemo-responsive shape memory effect in polymers: a sketch of working mechanisms, fundamentals and optimization. J Polym Res 19(9):1–34 Google Scholar
- Lendlein A, Kelch S (2002) Shape-memory polymers. Angewandte Chemie (Int ed Eng) 41(12):2035–2057Google Scholar
- Lu Q, Tang L, Lin F, Wang Q, Chen Y, Chen X, Huang B (2014) Preparation and characterization of cellulose nanocrystals via ultrasonication-assisted FeCl3-catalyzed hydrolysis. Cellulose. doi: 10.1007/s10570-014-0376-2
- Navarro-Baena I, Marcos-Fernandez A, Fernandez-Torres A, Kenny JM, Peponi L (2014a) Synthesis of PLLA-b–PCL-b–PLLA linear tri-block copolymers and their corresponding poly(ester-urethane)s: effect of the molecular weight on their crystallisation and mechanical properties. RSC Adv 4(17):8510–8524CrossRefGoogle Scholar
- Peponi L, Navarro-Baena I, Kenny JM (2014) Shape memory polymers: properties, synthesis and applications. In: Aguilar MR, San Román J (eds) Smart polymers and their applications. Woodhead Publishing, Cambridge, pp 204–236Google Scholar
- Raquez J-M, Vanderstappen S, Meyer F, Verge P, Alexandre M, Thomassin J-M, Jerome C, Dubois P (2011) Design of cross-linked semicrystalline poly(epsilon-caprolactone)-based networks with one-way and two-way shape-memory properties through diels–alder reactions. Chem Eur J 17(36):10135–10143CrossRefGoogle Scholar
- Rueda L, Saralegui A, Fernández d’Arlas B, Zhou Q, Alonso-Varona A, Berglund LA, Mondragon I, Corcuera MA, Eceiza A (2013a) In situ polymerization and characterization of elastomeric polyurethane-cellulose nanocrystal nanocomposite. Cell response evaluation. Cellulose 20(4):1819–1828CrossRefGoogle Scholar