Nanocomposites Assembled via Electrostatic Interactions between Cellulose Nanocrystals and a Cationic Polymer.

On account of their high strength and stiffness and their renewable nature, cellulose nanocrystals (CNCs) are widely used as a reinforcing component in polymer nanocomposites. However, CNCs are prone to aggregation and this limits the attainable reinforcement. Here, we show that nanocomposites with a very high CNC content can be prepared by combining the cationic polymer poly[(2-(methacryloyloxy)ethyl) trimethylammonium chloride] (PMETAC) and negatively charged, carboxylated CNCs that are provided as a sodium salt (CNC-COONa). Free-standing films of the composites can be prepared by simple solvent casting from water. The appearance and polarized optical microscopy and electron microscopy images of these films suggest that CNC aggregation is absent, and this is supported by the very pronounced reinforcement observed. The incorporation of 33 wt % CNC-COONa into PMETAC allowed increasing the storage modulus of this already rather stiff, glassy amorphous matrix polymer from 1.5 ± 0.3 to 6.6 ± 0.1 GPa, while the maximum strength increased from 11 to 32 MPa. At this high CNC content, the reinforcement achieved in the PMETAC/CNC-COONa nanocomposite is much more pronounced than that observed for a reference nanocomposite made with unmodified CNCs (CNC-OH).

One pot preparation of chitosan/hyaluronic acid-based triple network hydrogel via in situ click reaction, metal coordination and polyion complexation in water.

Development of biopolymer hydrogels with multiple networks is regarded as a way to obtain gel strengths with bio-related properties. The present work, for the first time, demonstrates preparation of one pot triple network hydrogel of chitosan (CS) and hyaluronic acid (HA) (HA-triazole/CS-Cu(II) gel), formed by triazole linkage, metal-coordination, and CS-HA polyion complexation. The salt containing water system favors polyion complex formation of CS and HA without precipitation. HA functionalized with alkyne and azide groups in aqueous EDC/NHS allows crosslinking of HA via triazole linkage using Cu(I) azide-alkyne Click chemistry (CuAAC). The required Cu(I) catalyst is generated from Cu(II) in the CS-Cu complex upon addition of sodium ascorbate. The CS/NHS system leads to the solubilization of CS, thus enabling ionic gelation. The mechanical properties and morphologies can be controlled by simply varying the CS-HA mole ratios. In addition, the CS-HA triple-network (TN) hydrogels show biocompatibility based on studies with chondrocyte cells.

Chitosan whisker grafted with oligo(lactic acid) nanoparticles via a green synthesis pathway: Potential as a transdermal drug delivery system.

Chitosan whisker (CSWK) grafted with oligo(lactic acid) (OLA) nanoparticles (NPs) in water is developed to aid transferring therapeutic agents through the skin in a transdermal drug delivery system. Although several works in the past have shown grafting of poly(lactic acid) onto chitosan, the present work shows a green grafting system for the first time. The nano-sized CSWK provided effective conjugation of lactic acid even in a heterogeneous water-based system followed by polycondensation to form OLA. The OLA chain length is controlled by the lactic acid content and modulates the lipophilicity of CSWK-OLA. This fine tunes not only the size of the NPs but also the encapsulation efficiency of the hydrophobic drug lidocaine. A detailed chemical structure analysis, including the factors related to the development of NPs, is presented and extends the studies to the model drug encapsulation and delivery.