Recent developments in montmorillonite and sepiolite filled regenerated cellulose nanocomposites: characterizations and properties

In recent years, the development of environmentally friendly materials obtained from renewable resources has attracted enormous attention due to the new sustainable development policies. Cellulose is a readily available, naturally occurring biodegradable and biocompatible linear polysaccharide. Recently, room temperature ionic liquids have been used as solvents to produce regenerated cellulose (RC) due to their attractive properties such as good chemical and thermal stability, low flammability, low melting point and ease of recycling. Polymer/nanofiller nanocomposites are believed to have strong potential to widen polymer applications due to its enhanced performance. It is also widely accepted that the incorporation of small amount of nanofiller (less than 5 wt.%) into bio-based matrices results in nano-biocomposite materials with enhanced mechanical, permeability and thermal properties. Montmorillonite (MMT) has a nanosized layered structure with large surface area thus providing sufficient interfacial regions in polymer nanocomposite. Besides, the needle like fibers based, natural hydrous magnesium silicate sepiolite has also been investigated due to its high surface area, unique geometry and its ability to form the hydrogen bonding with polymers as well as to disperse well in the matrix. This chapter aims to highlight the effect of the addition of two different types of nanofillers such as organically modified MMT and sepiolite to produce RC nanocomposites, on selected properties

Bionanocomposite regenerated cellulose/single-walled carbon nanotube films prepared using ionic liquid solvent

Electrically conductive regenerated cellulose/single-walled carbon nanotube (RC/CNT) bionanocomposite films were fabricated using an environmentally benign ionic liquid, 1-ethyl-3-methylimidazolium chloride (EMIMCl). CNTs were well dispersed in EMIMCl by employing ultrasonication prior to solution casting. The films were characterized by X-ray diffraction analysis, field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). Introduction of CNTs greatly improved the tensile strength and Young’s modulus of the bionanocomposite films, without compromising their elongation at break. Homogeneous dispersion of CNTs was confirmed by FESEM and TEM micrographs. The bionanocomposites exhibited a rapid insulator to conductor transition at CNT content as low as 0.75 wt%. Incorporation of CNTs also enhanced the thermal stability, oxygen barrier properties, as well as water absorption resistance

Biophysical properties of hydrogels for mimicking tumor extracellular matrix

The extracellular matrix (ECM) is an essential component of the tumor microenvironment. It plays a critical role in regulating cell-cell and cell-matrix interactions. However, there is lack of systematic and comparative studies on different widely-used ECM mimicking hydrogels and their properties, making the selection of suitable hydrogels for mimicking different in vivo conditions quite random. This study systematically evaluates the biophysical attributes of three widely used natural hydrogels (Matrigel, collagen gel and agarose gel) including complex modulus, loss tangent, diffusive permeability and pore size. A new and facile method was developed combining Critical Point Drying, Scanning Electron Microscopy imaging and a MATLAB image processing program (CSM method) for the characterization of hydrogel microstructures. This CSM method allows accurate measurement of the hydrogel pore size down to nanometer resolution. Furthermore, a microfluidic device was implemented to measure the hydrogel permeability (Pd) as a function of particle size and gel concentration. Among the three gels, collagen gel has the lowest complex modulus, medium pore size, and the highest loss tangent. Agarose gel exhibits the highest complex modulus, the lowest loss tangent and the smallest pore size. Collagen gel and Matrigel produced complex moduli close to that estimated for cancer ECM. The Pd of these hydrogels decreases significantly with the increase of particle size. By assessing different hydrogels' biophysical characteristics, this study provides valuable insights for tailoring their properties for various three-dimensional cancer models.Anna P. Cameron, Bijun Zeng, Yun Liu, Haofei Wang, Farhad Soheilmoghaddam, Justin Cooper-White, Chun-Xia Zha

Influence of the processing methods on the properties of poly(lactic acid)/halloysite nanocomposites

The influence of processing methods on the thermo-mechanical properties of poly (lactic acid) (PLA) nanocomposites were investigated by preparing nanocomposites reinforced by halloysite nanotubes (HNTs) (from 0 to 10 [w/w%]) using solution casting (SC) and melt compounding (MC) methods. Statistical analysis revealed that the processing methods have a significant influence on the tensile properties, where nanocomposites prepared by MC have higher tensile properties compared to those by SC. Experimental results illustrated higher tensile strength and a drop in ductility under the higher strain rate as compared to the low strain rate for PLA/HNTs nanocomposites. At lower concentrations micrographs revealed that, HNTs dispersion was better for SC films as compared to MC, but more prominent HNTs aggregation at higher loadings. MC nanocomposites exhibited a high crystallinity as compared to SC, due to the recrystallization and nucleation effects. The thermal stability and activation energy increased with addition of HNTs, regardless of the processing methods

Effect of HNTs modification in nanocomposite membrane enhancement for bacterial removal by cross-flow ultrafiltration system

This study investigated the potential of silver lactate (SL)-holloysite nanotube clay (HNTs) nano-filler embedded into the polyvinylidene fluoride (PVDF) polymer matrix as an antibacterial separator. Three different nanocomposite membranes were fabricated via phase inversion technique aimed to enhance the permeation flux and fouling resistance with complete bacterial rejection. HNT has been modified by N-β-(aminoethyl)-É£-aminopropyltrimethoxy silane (AEAPTMS) aiming for immobilization of SL on the surface HNT during dope preparation. Salmonella and Enterobacter aerogenes (E. aerogenes) were considered as two types of bacteria to be removed from contaminated water in this experimental work. Nanocomposite membranes were characterized and analyzed by thermal gravimetric analysis (TGA), Fourier transform infrared (FTIR), field emission scanning electron microscopy (FESEM) combined with energy dispersive X-ray (EDX), X-ray photoelectron spectroscope (XPS), atomic force microscopy (AFM), contact angle, molecular weight cut-off (MWCO) and tensile strength. Potential silver ion loss was assessed by measuring the silver content in the coagulation bath and in the UF permeate using inductive-coupled plasma mass spectrometer (ICP-MS). Moreover, antibacterial effect of the membrane was examined in terms of removal of microorganisms by filtration, Log Reduction Value (LRV) and thickness of inhibition zone. From the experimental results, the prepared nanocomposite membranes have shown more than 99% bacterial rejection, LRV of more than 3 and broad inhibition zones in the agar plate. In particular, the nanocomposite membrane consisting M-HNTs/SL/PVDF showed significant improvement in permeation flux and flux declination among all the tested membranes. It was also found that modification of HNTs resulted in reduction of silver leaching by uniform distributing of SL, which contributed to significant inhibition for both types of growth bacteria within 24 h of incubation