Cellulose nanofibril as a crosslinker to reinforce the sodium alginate/chitosan hydrogels.

Hydrogels derived from natural polymers have received great attention, but their practical applications are severely hindered by the relatively poor mechanical properties. In this work, cellulose nanofibril (CNF) was used as a crosslinker to reinforce the sodium alginate (SA)/chitosan (CS) hydrogels for drug sustained release. The CNF was prepared via a combined process of ball milling and deep eutectic solvents (DESs) pretreatment and characterized using SEM, FT-IR, and XRD. Furthermore, the microstructure, mechanical/biological properties and swelling performance of SA/CS/CNF hydrogels were investigated. Results showed that 1.0 wt% CNF addition led to the increases of 23.6% in storage modulus and 54.4% in loss modulus for the SA/CS/CNF hydrogels, indicating that CNF addition was effective in reinforcing the three-dimensional entangled networks of the hydrogels. Moreover, the presence of CNF was found to weaken the swelling performance of SA/CS/CNF hydrogels. When the synthesized SA/CS/CNF hydrogel with 1.0 wt% CNF was applied as a carrier for drug release, 50.8% reduction in the release rate in simulated gastric juice was achieved, demonstrating its outstanding sustained release properties. This work suggested that CNF might be conducive to enhancing the properties of SA/CS hydrogels, which can serve as an ideal polymeric carrier for drug release.

Polylactic acid based biocomposite films reinforced with silanized nanocrystalline cellulose.

Polylactic acid (PLA) and nanocrystalline cellulose (NCC) are promising biodegradable materials that have shown great potential in a wide range of healthcare and packaging applications. In the present work, PLA and NCC were compounded at various ratios to form biocomposite films via solution casting process. In order to improve the compatibility of PLA/NCC blends, the NCC was deliberately subjected to graft modification by 3-aminopropyltriethoxysilane (KH-550). The as-prepared PLA/NCC composite films were further characterized by using SEM, FTIR, X-ray diffraction, UV-visible spectra analysis, thermal analysis, air permeability and mechanical measurements. Results showed that silanized NCC (SNCC) addition had an important effect on the overall properties of PLA based composite films. The increased SNCC was found to impart improvement in air permeability, light resistance, thermal stability and mechanical properties to the PLA based composite films. Particularly, in comparison to the controlled sample, the obtained PLA based composite films with 0.5 wt % SNCC showed increases of 53.87%, 61.46% in the tensile strength and elongation at break, respectively. Moreover, PLA/SNCC composite films exhibited a decrease of 87.9% in air permeability compared with pure PLA film. Therefore, this work may offer an effective route for reinforcing PLA based composite films.

Preparation and characterization of polylactic acid/polyaniline/nanocrystalline cellulose nanocomposite films.

Polylactic acid (PLA) serves as an ideal matrix for preparing electrically conductive materials for electrode, electromagnetic shielding and functional biological material application. Here, an environmentally friendly PLA/polyaniline (PANI)/nanocrystalline cellulose (NCC) nanocomposite film was prepared. Effects of NCC loadings on the rheological behavior of PLA/PANI/NCC suspensions and the microscopic, thermal, mechanical and conductive properties of nanocomposite films were investigated. Results revealed that PLA was wrapped with PANI particles and NCC was uniformly distributed in the obtained nanocomposite films. The PLA/PANI/NCC films exhibited an electrical conductivity of up to 2.16 S∙m-1 with 1% NCC dosage. Besides, the viscosity and viscoelasticity of the PLA/PANI/NCC suspensions were decreased and the dispersion stability of the suspensions was improved with the incorporation of NCC. Furthermore, the mechanical strength of PLA/PANI/NCC nanocomposite films was significantly improved with the reinforcement effect of NCC. In presence of 4% NCC loading, the tensile strength (TS) and tensile modulus (TM) of PLA/PANI/NCC films had an increase of 38.1% and 89.1%, respectively, while the elongation at break (Eb) exhibited a decrease of 27.3%, as compared to that of PLA/PANI films. These results demonstrated that the as-prepared PLA/PANI/NCC nanocomposite film may have the potential to be used as a bio-based electrically conductive material.