Rapid preparation of PAM/N-CNT nanocomposite hydrogels by DEM frontal polymerization and its performance study

In this study, a simple and eco-friendly method was proposed to efficiently prepare nanocomposite hydrogels with excellent mechanical properties and satisfactory pH response behaviour by frontal polymerization (FP) of DEM in close to 4 minutes. Acrylamide (AM) and choline chloride (ChCl) were used as raw materials to synthesize deep eutectic monomers (DEMs). Nitrogen-doped carbon nanotubes were dispersed in DEMs as fillers, and poly(acrylamide)/nitrogen-doped carbon nanotube (PAM/N-CNT) nanocomposite hydrogels were prepared by FP. The non-covalent interactions between PAM hydrogels and N-CNTs was verified by Fourier infrared spectroscopy. The mechanical properties of PAM/N-CNT nanocomposite hydrogels were investigated, as well as the swelling and pH response properties. The results showed that the compressive strength of PAM hydrogels was significantly enhanced by the addition of N-CNTs due to the hydrophobic interaction of N-CNTs, which also causes sensitive response properties of the PAM hydrogels in acid solution.

In this study, a simple and eco-friendly method was proposed to efficiently prepare nanocomposite hydrogels with excellent mechanical properties and satisfactory pH response behaviour by frontal polymerization of DEM in close to 4 minutes.

Induced neural stem cell differentiation on a drawn fiber scaffold-toward peripheral nerve regeneration

To achieve regeneration of long sections of damaged nerves, restoration methods such as direct suturing or autologous grafting can be inefficient. Solutions involving biohybrid implants, where neural stem cells are grown in vitro on an active support before implantation, have attracted attention. Using such an approach, combined with recent advancements in microfabrication technology, the chemical and physical environment of cells can be tailored in order to control their behaviors. Herein, a neural stem cell polycarbonate fiber scaffold, fabricated by 3D printing and thermal drawing, is presented. The combined effect of surface microstructure and chemical functionalization using poly-L-ornithine (PLO) and double-walled carbon nanotubes (DWCNTs) on the biocompatibility of the scaffold, induced differentiation of the neural stem cells (NSCs) and channeling of the neural cells was investigated. Upon treatment of the fiber scaffold with a suspension of DWCNTs in PLO (0.039 g l^-1) and without recombinants a high degree of differentiation of NSCs into neuronal cells was confirmed by using nestin, galactocerebroside and doublecortin immunoassays. These findings illuminate the potential use of this biohybrid approach for the realization of future nerve regenerative implants.

Surface Mechanical Characterization of Carbon Nanofiber Reinforced Low-Density Polyethylene by Nanoindentation and Comparison with Bulk Properties

Surface mechanical properties of low-density polyethylene (LDPE) reinforced by carbon nanofibers (CNFs) up to 3% weight load were investigated using nanoindentation (NI). Surface preparation of the nanocomposite was thoroughly investigated and atomic force microscopy (AFM) was used to analyze the surface roughness of the polished surfaces. The dispersion of nanofillers in the LDPE matrix was examined using scanning electron microscopy (SEM). The effect of various penetration loads on the results and scattering of the data points was discussed. It was found by NI results that the addition of 3% weight CNF increased the elastic modulus of LDPE by 59% and its hardness up to 12%. The nano/micro-scale results were compared with macro-scale results obtained by the conventional tensile test as well as the theoretical results calculated by the Halpin-Tsai (HT) model. It was found that the modulus calculated by nanoindentation was twice that obtained by the conventional tensile test which was shown to be in excellent agreement with the HT model. Experimental results indicated that the addition of CNF to LDPE reduced its wear resistance property by reducing the hardness to modulus ratio. SEM micrographs of the semicrystalline microstructure of the CNF/LDPE nanocomposite along with the calculated NI imprints volume were examined to elaborate on how increasing the penetration depth resulted in a reduction of the coefficient of variation of the NI data/more statistically reliable data.

Poly(methyl methacrylate) end-functionalized with hexabenzocoronene as an effective dispersant for multi-walled carbon nanotubes

We demonstrate that single MWCNTs can be dispersed in organic solvents using a poly(methyl methacrylate) (PMMA) end-functionalized with hexabenzocoronene.

MWCNTs/Cellulose Hydrogels Prepared from NaOH/Urea Aqueous Solution with Improved Mechanical Properties

Novel high strength composite hydrogels were designed and synthesized by introducing multiwalled carbon nanotubes (MWCNTs) into cellulose/NaOH/urea aqueous solution and then cross-linked by epichlorohydrin. MWCNTs were used to modify the matrix of cellulose. The structure and morphology of the hydrogels were characterized by Fourier transform infrared (FT-IR) spectroscopy, high resolution transmission electron microscopy (HR-TEM), and scanning electron microscopy (SEM). The results from swelling testing revealed that the equilibrium swelling ratio of hydrogels decreased with the increment of MWCNTs content. Thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) results demonstrated that the introduction of MWCNT into cellulose hydrogel networks remarkably improved both thermal and mechanical properties of the composite hydrogels. The preparation of MWCNTs modifiedcellulose-based composites with improved mechanical properties was the first important step towards the development of advanced functional materials.

Metal-catalyst-free growth of carbon nanotubes/carbon nanofibers on carbon blacks using chemical vapor deposition

Carbon black can act as catalysts to grow carbon nanotubes or carbon nanofibers through a metal-catalyst-free thermal chemical vapor deposition.

Exfoliated Graphite Reinforced PMMA Composite: A Study on Nanoindentation and Scratch Behavior

The present work aims to compare the scratch hardness (Hs) with the indentation hardness (HIT) obtained from nanoindentation measurements of exfoliated graphite/poly (methyl methacrylate) (EG/PMMA) composites. EG/PMMA composites with thickness 50 μm each were produced by in situ melt mixing method. Scratch hardness was measured from the scratch width formed at low applied load during the course of the scratch measurements. The measured scratch hardness values were compared with the indentation hardness. There is a good correlation between the scratch hardness and the indentation hardness at low indentation depths, with a linear relationship between hardness and the reinforcement content of exfoliated graphite.