Morphology transition control of polyaniline from nanotubes to nanospheres in a soft template method

A soft template route is reported for the fabrication of polyaniline nanospheres via the oxidative polymerization of aniline in the presence of β‐naphthalenesulfonic acid (β‐NSA) as both surfactqant and dopant, and ammonium persulfate as oxidant at 2–5 °C. Control over the morphology and size of the nanoparticles was achieved by changing the reaction medium via addition of an organic cosolvent (i.e. ethanol or ethylene glycol) and by controlling the concentrations of aniline and β‐NSA and the molar ratio of β‐NSA to aniline. By this means the size of the β‐NSA–aniline micelles and the way that aniline monomer interacts with the micelles were controlled. In fact the lower dielectric constant of organic cosolvent, due to reduction of the possibility of dissociation of ionic species, causes the monomer to exist mostly as neutral aniline molecules rather than as anilinium cations. The neutral aniline molecules form aniline‐filled micelles with β‐NSA, which act as soft templates for the formation of polyaniline nanospheres. Scanning and transmission electron microscopies, dynamic light scattering, and Fourier transform infrared and UV‐visible spectroscopies were used to characterize the products. The mechanism of morphology transition from nanotubes to nanoparticles is discussed based on the experimental observations. © 2014 Society of Chemical Industry     

Design and Implementation of an Inverse Dynamics Controller for Uncertain Nonholonomic Robotic Systems

This paper addresses the trajectory tracking control problem of nonholonomic robotic systems in the presence of modeling uncertainties. A tracking controller is proposed such that it combines the inverse dynamics control technique and an adaptive robust PID control strategy to preserve robustness to both parametric and nonparametric uncertainties. A SPR-Lypunov stability analysis demonstrates that tracking errors are uniformly ultimately bounded (UUB) and exponentially converge to a small ball containing the origin. The proposed inverse dynamics tracking controller is successfully applied to a nonholonomic wheeled mobile robot (WMR) and experimental results are presented to validate the effectiveness of the proposed controller.     

The Influence of Neutron Irradiation on the Critical Temperature and Normal Phase Resistance of YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>7−<Emphasis Type="Italic">δ</Emphasis></Subscript> High Temperature Superconductors

The variation of the normal phase resistance, transition width and critical temperature T _c by the irradiation bulk samples of Y123 with different doses of neutrons at the temperature range of 70<T<300 K has been investigated comparatively. The nonirradiated sample shows a superconducting transition temperature of T _c=86 K (zero-resistance temperature). The irradiation produced clear enhancement of normal phase resistance at all investigated temperatures, which provides the evidence for the enhancement of residual resistance, so the results of experiments showed that the transition width and critical temperature of specimens varies nonlinearly with increasing irradiation fluencies. These results are explained in terms of oxygen declension, and some defects induced by neutrons.      

The influence of plasticizer molecular weight on spreading droplet size of HPMC aqueous solutions using an indirect method

Film coating is a complex process that involves many factors. To ensure spreading and/or film capability, plasticizers are added. The role of different molecular weights of polyethylene glycol on the behavior of hydroxypropylmethylcellulose (HPMC) with different grades was determined and compared with values for the film without the plasticizer using a real method for spreading. The droplet size, distribution, and shape were analyzed as the criterion. The results show that the polymer grades and plasticizer types are important in droplet size formation.     

Facile synthesis and characterization of TiO<Subscript>2</Subscript>–graphene–ZnFe<Subscript>2−<Emphasis Type="Italic">x</Emphasis></Subscript>Tb<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>4</Subscript> ternary nano-hybrids

Rare earth ion (Tb³⁺)-doped zinc ferrite (ZnFe₂O₄) nanoparticles grown on reduced graphene oxide (RGO) prepared through sol–gel method have been reported. During the sol–gel process, graphene oxide was reduced to RGO, and, subsequently, anatase TiO₂ and cubic spinel ZnFe_2?x Tb _x O₄ were grown in situ on the surfaces of the RGO nano-sheets. The structure, surface morphology and chemical composition of ternary nano-composites were studied using scanning electron microscopy, energy-dispersive X-ray, X-ray diffraction (XRD), Fourier transform infrared spectroscopy, photoluminescence spectra and vibrating sample magnetometer (VSM). XRD results showed that the produced TiO₂ was composed of anatase and some rutile phases and ZnFe₂O₄ with a cubic spinel structure. The particle sizes of ZnFe₂O₄ and TiO₂ nanoparticles were in the ranges of ~65–80 and ~17–20 nm, respectively. The saturation magnetization (M _S) determined from VSM was found to linearly increase with Tb³⁺ concentration.     

Temperature and frequency‐dependent creep and recovery studies on PVDF‐HFP/organo‐modified layered double hydroxides nanocomposites

A series of poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) loaded with various contents of layered double hydroxides (LDHs) nanoparticles were prepared via a melt mixing method. Detailed investigations on LDH dispersion state in the polymeric matrix conducted by TEM revealed intercalated/exfoliated, and agglomerated structures at low (1 wt %) and high (>3 wt %) loadings of LDH contents, respectively. Wide angle X‐ray scattering and DSC results showed that incorporation of LDH into PVDF‐HFP matrix reduced its overall crystallinity and helped to form polar crystallites, while the crystal size at 020 crystallographic directions was found to be most affected by presence and dispersion state of LDH in the matrix. TGA results showed LDH improved thermal stability of matrix however, unlike many other nanomaterials it significantly reduced the residual mass which highlights catalytic role of LDH in degradation of residual carbon char. Detailed analysis on creep and recovery data over wide range of selected temperatures revealed that the creep compliance of nanocomposites are basically controlled by crystallinity and presence of LDH at low and high temperatures, respectively. Based on obtained storage modulus and creep compliance master curves it was also found that the influence of LDH on decreasing the creep compliance and improving viscoelastic properties of PVDF‐HFP over long time period and over high frequency ranges becomes more pronounced. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46352.     

Mobility enhancement of solution-processed Poly(3-Hexylthiophene) based organic transistor using zinc oxide nanostructures

This work reports the mobility enhancement of p-type organic transistors formed using Poly(3-Hexylthiophene) (P3HT) using the dispersion of ZnO (zinc oxide) nanostructures. The ZnO nanostructures considered here are nanorods that were fabricated via a simple one-step aqueous-based chemical approach. Organic Thin Film Transistors (OTFTs) based on these nanocomposites show a mobility enhancement of more than 60% for the P3HT/ZnO nanorod composite compared to its pristine state polymer devices. The results presented here show a great promise for the mobility enhancement of p-type solution processed OFETs and applications.     

Cure kinetics of a polymer‐based composite friction material

In the present article, cure kinetics of a commercially available composite friction material used in railroad vehicles is investigated using the rheometer measurements. Effect of ingredients of friction material compound, including rubber matrix, phenolic resin, and fillers, on overall cure kinetics of friction compound is also investigated by comparing the cure kinetics of friction material and rubber matrix compound. A phenomenological model and an Arrhenius‐type equation is developed for cure kinetics and induction time of both friction material and rubber matrix. The parameters of the models are extracted from experimental data, using the rheometer at different temperatures and utilizing appropriate optimization method. The good agreement between experimental measurement and models prediction indicates the good performance of the models developed in this study. The results demonstrate that phenolic resin and fillers have dominant effects on the overall cure behavior of the friction material compound. A comparison between the present results and other published data based on the differential scanning calorimetry (DSC) shows a reasonable agreement as well. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 100: 9–17, 2006