Catégories
Natural, reborn and eco-friendly polymers for biomedical and other bioapplications (NRE-BIOPOL)

Atmospheric plasma: a simple way of improving the interface between natural polysaccharides and polyesters

Atmospheric plasma: a simple way of improving the interface between natural polysaccharides and polyesters

X Carette, R Mincheva, M Herbin, X Noirfalise, T C Nguyen, P Leclere, T Godfroid, H Kerdjoudj, O Jolois, M Boudhifa

Abstract :  In this study, a novel simple and fast method was developed of immobilizing a natural polysaccharide (chitosan) on a polylactide (PLA) surface. In order to overcome the lack of surface adhesion between the chitosan and the PLA due to incompatibility issues, atmospheric pressure plasma was used. The plasma activation was able to modify the PLA surface by generating surface chemistry proper for stabilizing the chitosan layer. The activation of the surface was monitored through water contact angle (WCA) measurements and X-ray photoelectron spectroscopy (XPS). Indeed, the introduction of new functionalities lowers the hydrophobicity of the PLA surface allowing an effective spreading and immobilization of the chitosan layer. The presence of chitosan on the polyester’s surface was proven by Fourier transform infrared spectroscopy (FTIR).

Catégories
Natural, reborn and eco-friendly polymers for biomedical and other bioapplications (NRE-BIOPOL)

Substantial Effect of Water on Radical Melt Crosslinking and Rheological Properties of Poly(Ε-Caprolactone)

Substantial Effect of Water on Radical Melt Crosslinking and Rheological Properties of Poly(Ε-Caprolactone)

Angelica Avella, Rosica Mincheva, Jean-Marie RAquez, Giada Lo Re

Abstract :  One-step reactive melt processing (REx) via radical reaction was evaluated with the aim of improving the rheological properties of poly(ε-caprolactone) (PCL). In particular, a water-assisted REx was designed under the hypothesis of increasing crosslinking efficiency with water as a low viscous medium in comparison with a slower PCL macroradicals diffusion in the melt state. To assess the effect of dry vs. water-assisted REx on PCL, its structural, thermo-mechanical and rheological properties were investigated. Water-assisted REx resulted in increased PCL gel fraction compared to dry REx (from 1 to 34 %), proving the rationale under the formulated hypothesis. From dynamic mechanical analysis and tensile tests, the crosslink did not significantly affect the PCL mechanical performance. Dynamic rheological measurements showed that higher PCL viscosity was reached with increasing branching/crosslinking and the typical PCL Newtonian behavior was shifting towards a progressively more pronounced shear thinning. A complete transition from viscous- to solid-like PCL melt behavior was recorded, demonstrating that higher melt elasticity can be obtained as a function of gel content by controlled REx. Improvement in rheological properties offers the possibility of broadening PCL melt processability without hindering its recycling by melt processing.

Catégories
Natural, reborn and eco-friendly polymers for biomedical and other bioapplications (NRE-BIOPOL)

Epimerization and chain scission of polylactides in the presence of TBD

Epimerization and chain scission of polylactides in the presence of TBD

Julie Meimoun, Audrey Favrelle,-Huret, Marc Bria, Nicolas Merle, Grégory Stoclet, Julien De Winter, Rosica Mincheva, Jean-Marie Raquez, Philippe Zinck

Abstract :  The epimerization of polylactide is reported in the presence of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) at 105 °C in toluene. The extent of the reaction depends on the amount of TBD introduced and the reaction time. Up to ca. 46% D units can be formed starting from poly(l-lactide) in the presence of 5 mol% TBD. The epimerization rate is slightly higher for D-stereoisomers vs. L-stereoisomers. From the decrease of the number-average molecular weight observed, a concomitant chain scission reaction is observed. A possible mechanism based on a nucleophilic attack of TBD is proposed based on NMR analyses, notably DOSY, MALDI ToF mass spectrometry and IR spectroscopy. The implications of the work in the field of polymer synthesis and chemical recycling of polylactide are discussed.

Catégories
Natural, reborn and eco-friendly polymers for biomedical and other bioapplications (NRE-BIOPOL)

Interfacial compatibilization of PLA and Mg in composites for bioresorbable bone implants

Interfacial compatibilization of PLA and Mg in composites for bioresorbable bone implants

M Ben Abdeljawad, X Carette, R Mincheva, J. Odent1 and J-M Raquez

Abstract :  In this study, polylactide (PLA)/magnesium (Mg) composites were produced through extrusion and compression-molding. In order to enhance the interfacial adhesion between the hydrophobic matrix and the hydrophilic filler, an amphiphilic PEO-b-PLLA block copolymer was used. The morphological study shows an effective improvement of the PLA/Mg interactions following the copolymer addition. Moreover, the surface contact angle test proves the decrease of the PLA hydrophobicity. Thus, a significant influence on the cell adhesion is expected. Furthermore, hydroxyapatite formation in bulk after eight weeks of the immersion in a simulated body fluid (SBF) is also shown, suggesting that the bioactivity will be noticeably improved. However, a decrease in mechanical properties and cell adhesion is observed.

Catégories
Natural, reborn and eco-friendly polymers for biomedical and other bioapplications (NRE-BIOPOL)

Design of melt-recyclable poly(ε-caprolactone)-based supramolecular shape-memory nanocomposites

Design of melt-recyclable poly(ε-caprolactone)-based supramolecular shape-memory nanocomposites

Florence Pilate, Zhi-Bin Wen, Farid Khelifa, Yan Hui, Sebastien Delpierre, Luo Dan, Rosica Mincheva, Philippe Dubois, Ke-ke Yang, Jean-Marie Raquez

Abstract :  A novel poly(epsilon-caprolactone) (PCL) supramolecular network exhibiting shape-memory behavior was successfully constructed with pendant UPy units that are highly able to dimerize. The dynamic network was obtained by a simple and versatile strategy consisting of chain-extension reaction between α,ω-dihydroxyoligoPCL and hydroxylated UPy units in the presence of hexamethylene diisocyanate as a coupling agent and further intermolecular dimerization of the UPy along the polyurethane backbone. 1H NMR analyses confirmed the dynamic features of the system, and DMTA in tensile mode was investigated to assess the SMP properties. Recyclability was also assessed by taking advantage of these supramolecular networks. Further addition of cellulose nanocrystals into the polymer network enabled adjustment of the extent of the net-points and therefore the SMP features. As confirmed by dispersion tests in solution and SEM observations, these bio-based nanofillers were homogeneously distributed in the network via supramolecular interaction between the hydroxyl groups present on their surface and UPy moieties along the polyurethane backbone. Thus, the here developed nanomaterials might reveal applicability in areas where a combination of SMP and biocompatibility is needed.