All issues / Volume 7 (2013) / Issue 9 (September)
This is an editorial article. It has no abstract.
Present work reports novel synthesis of Polyaniline (PANI)/Se nanocomposites. Se nanowires are prepared from SeO2 under assistance of vitamin C and polyaniline is synthesized through chemical oxidation. The effect of composition of Se nanowires on the properties of polyaniline was investigated and five orders increase in conductivity after doping has been observed. The electrical properties of nanocomposites show that conduction is through hopping process due to the wide range of localized states present near fermi level. FTIR (Fourier Transform Infrared spectroscopy) and ultraviolet (UV)-visible studies confirm the occurrence of polyaniline in conducting emeraldine salt form in the composites and suggest incorporation of Se in polymer. The optical studies indicate that absorption mechanism is due to indirect allowed transition and the optical band gap tends to decrease after doping. The thermal stability of composites has been ascertained on the basis of DSC (Differential Scanning Calorimetery) measurements. TEM (Transmission Electron Microscopy) and SEM (Scanning Electron Microscopy) analysis have also been carried out for morphological studies.
Guar gum (GG) and Guar gum/borax (GGb) hydrogels are studied by means of rheology, Low Field Nuclear Magnetic Resonance (LF NMR) and model drug release tests. These three approaches are used to estimate the mesh size (ζ) of the polymeric network. A comparison with similar Scleroglucan systems is carried out. In the case of GGb, the rheological and Low Field NMR estimations of ζ lead to comparable results, while the drug release approach seems to underestimate ζ. Such discrepancy is attributed to the viscous effect of some polymeric chains that, although bound to the network to one end, can freely fluctuate among meshes. The viscous drag exerted by these chains slows down drug diffusion through the polymeric network. A proof for this hypothesis is given by the case of Scleroglucan gel, where the viscous contribution is not so significant and a good agreement between the rheological and release test approaches was found.
We report a method to prepare the poly(vinyl alcohol)/reduced graphene oxide (PVA/rGO) nanocomposites with low percolation threshold and high electrical conductivity by using the large-area reduced graphene oxide (LrGO) sheets. The large-area graphene oxide (LGO) sheets are expected to overlap better with each other and form the continuous GO network in PVA matrix than small-area graphene oxide (SGO). During the thermal reduction process, the LGO sheets are easily restored and improve the electrical conductivity of nanocomposites due to their low damage level of conjugate-structure. As a result, the percolation threshold of PVA/LrGO nanocomposites is ~0.189 wt% lower than present reports (0.5~0.7 wt%). At the LrGO content of 0.7 wt%, the electrical conductivity of PVA/LrGO nanocomposites reaches 6.3•10–3 S/m. Besides that, this method only takes 15~30 min to reduce the PVA/GO nanocomposites effectively.
Electrically conductive bacterial cellulose composite membranes produced by the incorporation of graphite nanoplatelets in pristine bacterial cellulose membranes
T. Zhou, D. Chen, J. Jiu, T. T. Nge, T. Sugahara, S. Nagao, H. Koga, M. Nogi, K. Suganuma, X. Wang, X. Liu, P. Cheng, T. Wang, D. Xiong
Vol. 7., No.9., Pages 756-766, 2013
Vol. 7., No.9., Pages 756-766, 2013
Graphite nanoplatelets (GNPs) were utilized to improve the electrical conductivity of pristine bacterial cellulose (BC) membranes. By physical and chemical methods, flake-shaped GNPs, weaving through the surface layer of web-like cellulose nanofibrils, were indeed fixed or trapped by the adjacent nanofibrils in the BC surface network, for comparison, rod-shaped multi-walled carbon nanotubes (MWCNTs) were homogeneously inserted into BC membrane through the pore structures and tunnels within the BC membrane. Strong physical and chemical interaction exists between the BC nanofibrils and the particles of GNP or MWCNT even after 15 h sonication. BC membrane with 8.7 wt% incorporated GNPs reached the maximum electrical conductivity of 4.5 S/cm, while 13.9 wt% MWCNT/BC composite membrane achieved the maximum electrical conductivity of 1.2 S/cm. Compared with one dimensional (1-D) MWCNTs, as long as GNPs inserted into BC membranes, the 2-D reinforcement of GNPs was proven to be more effective in improving the electrical conductivity of BC membranes thus not only break the bottleneck of further improvement of the electrical conductivity of BC-based composite membranes but also broaden the applications of BC and GNPs.
The current study focuses on three-components material systems (poly(lactic acid) (PLA), poly(ε-caprolactone) (PCL) and wollastonite (W)) in view of possible application a biomedical scaffold constructs. Melt extruded PLA/PCL/W composites (PLCL15, PLCLW1, PLCLW4, PLCLW8 containing 0, 1, 4, 8 phr filler respectively) are batch foamed using compressed CO2 and the porous foams are studied for in vitro biocompatibility by seeding osteoblast cells. SEM images of the unfoamed polymers show immiscibility in all compositions. Materials have been tested under compressive load using dry and wet conditions (using phosphate buffered saline at pH 7.4) for in vitro study. Contact angle measurement shows enhanced hydrophilicity in the composites changing from 80° in PLCL15 to 72° in PLCLW8. The foams are found to be microcellular (5–8 µm) in morphology showing quite uniform pore distribution in the composites. The prepared foams, when studied as scaffold constructs, show osteoblast cell attachment and proliferation over the incubation period of 7 days. As expected, PLCLW8 containing highest amount of CaSiO3 supported maximum cell growth on its surface as visible from MTT assay data and SEM scans.
Structural characteristics and enhanced mechanical and thermal properties of full biodegradable tea polyphenol/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) composite films
H. X. Xiang, S. H. Chen, Y. H. Cheng, Z. Zhou, M. F. Zhu
Vol. 7., No.9., Pages 778-786, 2013
Vol. 7., No.9., Pages 778-786, 2013
Full biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) composite films were prepared with 5~40 wt% green tea polyphenol (TP) as toughener. The effects of mixing TP on mechanical properties, thermal properties and hydrophilic-hydrophobic properties of composite films were investigated. Tension test results show that the incorporation of TP in the PHBV matrix can enhance the toughness of the composite films. Differential scanning calorimetric (DSC) studies show that there is a single glass transition temperature and the lower melting point temperature. Fourier transform infrared (FT-IR) results confirm that the intermolecular hydrogen bonding interactions in composite films. Contact angle measurements show that the hydrophilicity of TP/PHBV composite films can be controlled through adjusting the composition of TP.
Low odour-emissive polylactide/cellulose fibre biocomposites, intended for car interior, were prepared and characterised. The impact of the different stages of processing (drying cycles, compounding, injection moulding) on the extent of polylactide degradation and on biocomposites properties was investigated by size exclusion chromatography, thermogravimetry, differential scanning calorimetry. In parallel, the odour emission of these materials was quantified via dynamic dilution olfactometry and Field of odours® method. The changes in molecular weight and global odour emission indicated that compounding had a strong impact on polylactide degradation and odour emission, while injection moulding had no significant impact. Adding 0.5 wt% of an absorbent agent based on poly(1-methylpyrrol-2-ylsquaraine could) divide the global odour concentration by a factor 2. The morphology, mechanical and thermal properties of injection moulded PLAbiocomposites were not affected by the presence of the absorbent agent.