Nerve repair: a conducting-polymer platform with biodegradable fibers for stimulation and guidance of axonal growth (adv. Mater. 43/2009)

Effective functional innervation of medical bionic devices, as well as re-innervation of target tissue in nerve and spinal cord injuries, requires a platform that can stimulate and orientate neural growth. Gordon Wallace and co-workers report on p. 4393 that conducting and nonconducting biodegradable polymers show excellent potential as suitable hybrid substrata for neural regeneration and may form the basis of electrically active conduits designed to accelerate nerve repair.

Structural transformation of polyacrylonitrile fibers during stabilization and low temperature carbonization

The effect of oxidative stabilization and carbonization processes on the structure, mass and mechanical properties of polyacrylonitrile (PAN) precursor fibers was analyzed. A gradual densification of the fibers occurring from mass loss, decrease in fiber diameter and increase in density were observed after stabilization at a maximum temperature of 255 °C and carbonization at a maximum temperature of 800 °C. The tensile strength and modulus of the fibers were found to decrease after stabilization but then increased after low temperature carbonization. The thermal processing of the precursor fibers affected their mode of failure after tensile loading, changing from a ductile type of failure to a brittle type. The type of failure correlated well with the crystal structure changes in the fibers. Whilst the PAN precursor fiber started to exotherm above 225 °C in air, no prominent exothermic reaction was measured in the carbonized fibers in air up to 430 °C. The aromatization index of stabilized fiber was calculated to be ∼66%, and that of carbonized fiber was ∼99%. FTIR studies indicated that the variation in the chemical structure of the fibers with the stabilization of the fibers. Radial heterogeneity in the stabilized fibers was observed however it was not promoted to the carbonized fibers. Finally, a method to calculate mass retention of PAN precursor fiber after heat treatment was developed, and the calculated percentage mass retained of the precursor fiber after oxidation and carbonization were found to be 81% and 51%, respectively. . This study proposes an effective method to calculate the percentage of mass retained by precursor fibers after stabilization and low temperature carbonization to provide a model for evaluating carbon fiber yield from a given amount of fibers.

Interactions between fibroin and sericin proteins from antheraea pernyi and bombyx mori silk fibers

Silkworm silk fibers are core-shell composites of fibroin and sericin proteins. Studying the interactions between fibroin and sericin is essential for understanding the properties of these composites. It isobserved that compared to the domestic silk cocoon Bombyx mori (B. mori), the adhesion between fibroin and sericin from the wild silk cocoon, Antheraea pernyi (A. pernyi), is significantly stronger with a higherdegree of heterogeneity. The adsorption of A. pernyi sericin on its fibroin is almost twice the value for B.mori sericin on fibroin, both showing a monolayer Langmuir adsorption. 1H NMR and FTIR studiesdemonstrate on a molecular level the stronger interactions and the more intensive complex formation between A. pernyi fibroin and sericin, facilitated by the hydrogen bonding between glycine and serine.The findings of this study may help the design of composites with superior interfacial adhesion between different components.

Electrical conductivity of single walled and multiwalled carbon nanotube containing wool fibers

The main purpose of this study was producing conductive wool fabric applying carbon nanotubes. Raw and oxidized wool samples were treated with carbon nanotubes in the impregnating bath in the presence of citric acid as a crosslinking agent and sodium hypophosphite as a catalyst while sonicating them in the ultrasonic bath. Electrical resistance, washing durability, and color variation of treated samples were assessed. Through SEM images, the surface morphology of treated samples was studied confirming the surface coating through carbon nanotubes. According to the results, the electrical resistance of treated wool with carbon nanotubes reduced substantially. However, the single-walled carbon nanotubes are more useful to increase the conductivity. In addition, the wool color changed into gray after the treatment.

The role of nano colloid of TiO2 and butane tetra carboxylic acid on the alkali solubility and hydrophilicity of proteinous fibers

One of the main problems of wool as an important proteinous fiber is low resistance against alkali media. Finding a way to solve this problem without any influences on other fiber characteristics is still a matter of research. Using nano particles on textile materials is a new approach to produce novel properties. Here, nano titanium dioxide (NTO) particles along with butane tetra carboxylic acid (BTCA) were sonicated in the ultra sound bath and applied as a nano colloid on the wool fabric. BTCA played different roles as wool cross-linker, a polyanionic agent, and stabilizer for nano TiO2. Various concentrations of NTO and BTCA were applied through impregnation of the fabric in ultrasonic bath followed by curing. The resistance of fabrics against alkali was assessed by solubility in sodium hydroxide and the hydrophilicity monitored by the water drop absorption time and the contact angle before and after UV irradiation. Interestingly, the alkali solubility of the nano TiO2 treated wool fabrics reduced while the fabric became more hydrophilic. This fact was shown by the testing results and is thoroughly discussed in the article. The response surface methodology (RSM) was also applied to find the optimum conditions for the wool fabric treatment.

Enhanced homogeneity and interfacial compatibility in melt-extruded cellulose nano-fibers reinforced polyethylene via surface adsorption of poly(ethylene glycol)-block-poly(ethylene) amphiphiles

In this paper, we demonstrate that an amphiphilic block copolymer such as polyethylene glycol-b-polyethylene can be used as both dispersing and interfacial compatibilizing agent for the melt compounding of LLDPE with cellulose nano-fibers. A simple and effective spray drying methodology was first used for the first time for the preparation of a powdered cellulose nano-fibers extrusion feedstock. Surface adsorption of the amphiphilic PEG-b-PE was carried out directly in solution during this process. These various dry cellulosic feedstock were subsequently combined with LLDPE via extrusion to produce a range of nano-composites. The collective outcomes of this research are several folds. Firstly we show that presence of surface adsorbed PEG-b-PE effectively hindered the aggregation of the cellulose nano-fibers during the extrusion, affording clear homogenous materials with minimum aggregation even at the highest loading of cellulose nano-fibers (∼23 vol.%). Secondly, the tailored LLDPE/cellulose interface arising from intra- and inter-molecular hydrogen and Van der Waals bonds yielded significant levels of mechanical improvements in terms of storage and tensile modulus. We believe this study provides a simple technological template to produce high quality and performant polyolefins cellulose-based nano-composites.

Cellulose-derived carbon fibers produced via a continuous carbonization process: investigating precursor choice and carbonization conditions

Here, the carbonization of two Lyocell type regenerated cellulose fibres is reported. Commercially available Lyocell as well as the experimental Lyocell type fibre known as Ioncell-F spun from the ionic liquid 1,5-diazabicyclo[4.3.0]non-5-ene-1-ium acetate ([DBNH]OAc) is investigated, which supports higher draw ratio and thus improves precursor mechanical properties. Lyocell fibres are known to have improved mechanical properties over other regenerated cellulose fibres and are therefore considered to be better carbon fibre precursor candidates. The Lyocell fibres used in this study are carbonized utilizing a scaled down identical replica of an in use carbon fibre line. The importance of this is the ability to assess the performance of the Lyocell fibres under more realistic continuous carbonization processing conditions. The tensile properties, morphology, and chemical composition of all fibres are determined. It is shown that by changing the carbonization temperature and atmosphere fibres with different mechanical properties and diameter can be produced. Elemental analysis confirms that each fibre has a carbon content of ≥90%.