The present work highlights the crucial role of the interfacial compatibilization on the design of polylactic acid (PLA)/Magnesium (Mg) composites for bone regeneration applications. In this regard, an amphiphilic poly(ethylene oxide-b-L,L-lactide) diblock copolymer with predefined composition was synthesised and used as a new interface to provide physical interactions between the metallic filler and the biopolymer matrix. This strategy allowed (i) overcoming the PLA/Mg interfacial adhesion weakness and (ii) modulating the composite hydrophilicity, bioactivity and biological behaviour. First, a full study of the influence of the copolymer incorporation on the morphological, wettability, thermal, thermo-mechanical and mechanical properties of PLA/Mg was investigated. Subsequently, the bioactivity was assessed during an in vitro degradation in simulated body fluid (SBF). Finally, biological studies with stem cells were carried out. The results showed an increase of the interfacial adhesion by the formation of a new interphase between the hydrophobic PLA matrix and the hydrophilic Mg filler. This interface stabilization was confirmed by a decrease in the damping factor (tanδ) following the copolymer addition. The latter also proves the beneficial effect of the composite hydrophilicity by selective surface localization of the hydrophilic PEO leading to a significant increase in the protein adsorption. Furthermore, hydroxyapatite was formed in bulk after 8 weeks of immersion in the SBF, suggesting that the bioactivity will be noticeably improved by the addition of the diblock copolymer. This ceramic could react as a natural bonding junction between the designed implant and the fractured bone during osteoregeneration. On the other hand, a slight decrease of the composite mechanical performances was noted.

An innovative mixing device RMX (Reactor/elongational flow MiXer), based on an elongational flow, is used to formulate new biocomposites based on Doum palm fiber (at various proportions) and PLA polymer. Due to its high elongational flow, RMX has the ability to mix immiscible products and to disperse the solid phase (fiber) in the viscous phase. The morphological aspect of PLA/Palm composites shows a good appearance and high fiber orientation and dispersive efficiency as confirmed by X‐ray tomography. For higher fiber content, the porosity rate decreases from 19% for untreated biocomposites to 11% for the treated ones. An enhancement of crystallinity degree is also recorded, mainly for alkali treated PLA biocomposites. This is explained by the nucleating effect of palm fiber which could favor the germination and the growth of spherolites around reinforcements. Moreover, the tensile performances show a progressive increase in Young moduli and a decrease in tensile strength upon increasing the fibers fraction and applying alkaline treatment. We highlight an enhancement in Young moduli at about 50% and 9% for treated ones compared to PLA matrix and untreated systems respectively. These improvements are attributed to the enhancement and improvement of interfacial adhesion as confirmed by scanning electron microscopy (SEM), carried out on fractured surfaces. In addition, viscoelastic behavior was evaluated by DMA analysis and further discussed. POLYM. COMPOS., 39:E519–E530, 2018. © 2017 Society of Plastics Engineers

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