High-Humidity Shaker Aging to Access Chitin and Cellulose Nanocrystals.

To unlock nature's potential for functional biomaterials, many efforts have been devoted to isolating the nanocrystalline domains within the supramolecular structure of polysaccharides. Yet, low reactivity and yield in aqueous systems along with excessive solvent usage hinders its development. In this report, the first solvent-free pathway to access carboxylated chitin and cellulose nanocrystals with excellent mass balance is described, relying on a new method coined high-humidity shaker aging (HHSA). The method involves a mild grinding of the polysaccharide with ammonium persulfate followed by an aging phase under high-humidity and on a shaker plate. Insights into the mechanism were uncovered, which highlighted the unique role of high humidity to afford a gradual uptake of water by the material up to deliquescence when the reaction is complete. This process was then validated for direct synthesis of nanocrystals from biomass sources including crab and soft wood pulp.

Mechanochemical Transformations of Biomass into Functional Materials.

Biomass is one of the promising alternatives to petroleum-derived materials and plays a major role in our fight against climate change by providing renewable sources of chemicals and materials. Owing to its chemical and structural complexity, the transformation of biomass into value-added products requires a profound understanding of its composition at different scales and innovative methods such as combining physical and chemical processes. In this context, the use of mechanochemistry in biomass valorization is currently growing owing to its potentials as an efficient, sustainable, and environmentally friendly approach. This review highlights the latest advances in the transformation of biomass (i. e., chitin, cellulose, hemicellulose, lignin, and starch) to functional materials using mechanochemical-assisted methods. We focused here on the methodology of biomass processing, influencing factors, and resulting properties with an emphasis on achieving functional materials rather than breaking down the biopolymer chains into smaller molecules. Opportunities and limitations associated this methodology were discussed accordingly for future directions.

Epoxidized Block and Statistical Copolymers Reinforced by Organophosphorus-Titanium-Silicon Hybrid Nanoparticles: Morphology and Thermal and Mechanical Properties.

Glycidyl methacrylate (GMA) and a mixture of alkyl methacrylates (average chain length of 13 carbons; termed C13MA; derived from vegetable oils) were copolymerized by nitroxide-mediated polymerization to form epoxidized statistical and block copolymers with similar compositions (F GMA ∼0.8), which were further cross-linked by a bio-based diamine. Hybrid plate-like nanoparticles containing organophosphorus-titanium-silicon (PTS) with an average size of ∼130 nm and high decomposition temperature (485 °C) were synthesized via a hydrothermal reaction to serve as additives to simultaneously enhance the thermal and mechanical properties of the blend. Nanocomposites filled with PTS were prepared at different filler-loading levels (0.5, 2, 4 wt %). Transmission electron microscopy (TEM) of the cured block copolymer displayed reaction-induced macrophase-separated domains. TEM also showed an effective dispersion of PTS hybrids in the matrix without intense agglomeration. Thermogravimetric analysis at different heating rates revealed the activation energy of poly (GMA-stat-C13MA) at maximum decomposition increased from 143.5 to 327.2 kJ mol-1 with 4 wt % PTS. Decomposition temperature and char residue improved 12 °C and ∼7 wt %, respectively, and T g increased 12 °C by adding 4 wt % PTS. Targeting various PTS concentrations enabled tuning of the tensile modulus (up to 75%), tensile strength (up to 46%), and storage modulus in both glassy state (up to 59%) and rubbery plateau regions (up to 88%). Oscillatory frequency sweeps indicated that PTS makes the storage modulus frequency dependent, suggesting that the inclusion of the nanoparticles alters the relaxation of the surrounding matrix polymer.

A comprehensive study on the fabrication and properties of biocomposites of poly(lactic acid)/ceramics for bone tissue engineering.

The fabrication of a suitable scaffold material is one of the major challenges for bone tissue engineering. Poly(lactic acid) (PLA) is one of the most favorable matrix materials in bone tissue engineering owing to its biocompatibility and biodegradability. However, PLA suffers from some shortcomings including low degradation rate, low cell adhesion caused by its hydrophobic property, and inflammatory reactions in vivo due to its degradation product, lactic acid. Therefore, the incorporation of bioactive reinforcements is considered as a powerful method to improve the properties of PLA. This review presents a comprehensive study on recent advances in the synthesis of PLA-based biocomposites containing ceramic reinforcements, including various methods of production and the evaluation of the scaffolds in terms of porosity, mechanical properties, in vitro and in vivo biocompatibility and bioactivity for bone tissue engineering applications. The production routes range from traditional approaches such as the use of porogens to provide porosity in the scaffolds to novel methods such as solid free-form techniques.