R.R. Deshmukh

Highly dispersible graphene oxide reinforced polypyrrole/polyvinyl alcohol blend nanocomposites with high dielectric constant and low dielectric loss

In the present study, we report the fabrication and characterizations of flexible dielectric nanocomposites consisting of water soluble polypyrrole (WPPy)/polyvinyl alcohol (PVA)/graphene oxide (GO) at different GO loadings (0.5–3 wt%). The WPPy/PVA/GO nanocomposites were characterized using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, UV-vis spectroscopy (UV), X-ray diffraction (XRD), thermogravimetric analysis (TGA), polarized optical microscopy (POM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). FTIR studies indicate the strong chemical interaction between GO and polymer systems. SEM results confirm that GO was homogeneously dispersed within the polymer matrix. The nanocomposites exhibit significant enhancement in the dielectric constant with low dielectric loss values as a function of GO loading which resulted from the fine dispersion of GO in the polymer matrix. The dielectric constant increases from (e = 27.93, 50 Hz, 150 °C) for WPPy/PVA (50/50) blend to (e = 155.18, 50 Hz, 150 °C) for nanocomposites with 3 wt% GO loading and the dielectric loss increases from (tan δ = 2.01, 50 Hz, 150 °C) for WPPy/PVA (50/50) blend to (tan δ = 4.71, 50 Hz, 150 °C) for nanocomposites with 3 wt% GO loading. Thus, these high-κ WPPy/PVA/GO nanocomposites are potential flexible high-performance dielectric materials for electronic devices such as high-frequency capacitors or embedded capacitors.

Influence of K2CrO4 Doping on the Structural, Optical and Dielectric Properties of Polyvinyl Alcohol/K2CrO4 Composite Films

ABSTRACT Polyvinyl alcohol/potassium chromate (K2CrO4) composite films were prepared by solution casting technique using distilled water as a solvent, and were further investigated using Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, X-ray diffraction, thermogravimetric analysis, optical microscopy, scanning electron microscopy, and dielectric measurements. Microscopic studies reveal that K2CrO4 was homogenously mixed with polyvinyl alcohol matrix due to interfacial interaction between polyvinyl alcohol and K2CrO4. The composite films showed very high dielectric constant and relatively low dielectric loss. Hence, such composite materials with improved dielectric properties could be useful for fabrication of electrical charge storage device. GRAPHICAL ABSTRACT

Eco-Friendly Synthesis of Graphene Oxide Reinforced Hydroxypropyl Methylcellulose/Polyvinyl Alcohol Blend Nanocomposites Filled with Zinc Oxide Nanoparticles for High-k Capacitor Applications

ABSTRACT Polymer/inorganic nanocomposites comprising of hydroxypropyl methylcellulose and polyvinyl alcohol as a polymer matrix and unique combination of graphene oxide and zinc oxide nanoparticles as fillers have been prepared using colloidal processing technique and characterized using various analytical methods. The dielectric properties of the nanocomposites are investigated using impedance analyzer. The nanocomposites show improvement in the dielectric properties compared to hydroxypropyl methylcellulose/polyvinyl alcohol (50/50) blends, which results from the homogeneous dispersion of fillers into the polymer matrix. The results indicate that these nanocomposites have a potential to meet the technological demands of high-k dielectrics and/or embedded capacitors. GRAPHICAL ABSTRACT

Influence of operating parameters on surface properties of RF glow discharge oxygen plasma treated TiO2/PET film for biomedical application

In this paper, a thin transparent titania (TiO2) film was coated on the surface of flexible poly(ethylene terephthalate) (PET) film using the sol-gel method. The surface properties of the obtained TiO2/PET film were further improved by RF glow discharge oxygen plasma as a function of exposure time and discharge power. The changes in hydrophilicity of TiO2/PET films were analyzed by contact angle measurements and surface energy. The influence of plasma on the surface of the TiO2/PET films was analyzed by atomic force microscopy (AFM) as well as the change in chemical state and composition that were investigated by X-ray photo electron spectroscopy (XPS). The cytotoxicity of the TiO2/PET films was analyzed using human osteoblast cells and the bacterial eradication behaviors of TiO2/PET films were also evaluated against Staphylococcus bacteria. It was found that the surface roughness and incorporation of oxygen containing polar functional groups of the plasma treated TiO2/PET films increased substantially as compared to the untreated one. Moreover the increased concentration of Ti(3+) on the surface of plasma treated TiO2/PET films was due to the transformation of chemical states (Ti(4+)→Ti(3+)). These morphological and chemical changes are responsible for enhanced hydrophilicity of the TiO2/PET films. Furthermore, the plasma treated TiO2/PET film exhibited no citotoxicity against osteoblast cells and antibacterial activity against Staphylococcus bacteria which can find application in manufacturing of biomedical devices.

Effects of operating parameters on DC glow discharge plasma induced PET film surface

A DC glow discharge plasma surface modification techniques are used to modify surface properties of polymeric materials such as adhesivity, hydrophobicity, hydrophilicity and biocompatibility. The plasma interaction with the surface produces modifications of its chemical structure and morphology. The objective of this study is to examine the effect of operating parameters such as discharge potential, pressure and exposure time on surface properties of polyethylene terephthalate (PET) film. The changes in hydrophilic properties of PET films were studied in detail using contact angle and surface energy measurements. The surface morphology and chemical composition of plasma modified film surfaces were studied by atomic force microscopy (AFM) and X-ray photo electron spectroscopy (XPS). It was found that the efficiency of the surface treatment increases with increasing discharge potential, pressure and exposure time. The AFM and XPS analysis showed changes in surface topography and formation of polar groups on the plasma modified PET surfaces.

Effect of TEOS plasma polymerization on corn starch/poly(ε-caprolactone) film: characterization, properties and biodegradation

Polymeric packaging materials are preferred because they are lightweight and cost-effective as compared to conventional packaging. Plasma enhanced chemical vapor deposition (PECVD) of organo-silicon compounds is one of the ways to deposit silicon oxide (SiOx) coating on polymers to improve barrier properties. In this paper, a tetraethyl orthosilicate (TEOS) precursor was used to deposit a SiOx coating on corn starch/poly(e-caprolactone) (CSPCL) films through PECVD. The effect of the deposition time on various properties was studied. ATR-FTIR, XPS and XRD revealed that the coating has a highly cross-linked SiOx glass like structure. AFM and SEM suggested a smooth and conformal morphology. Adhesive properties were studied from the peel strength and correlated with the work of adhesion. Barrier properties were studied from the water vapor and the oxygen transmission rates and showed significant improvement. The effect of the plasma polymerized TEOS (ppTEOS) coating on the biodegradation of CSPCL films was evaluated using an indoor soil burial method (to simulate natural degradation) with the single micro-organism, Bacillus subtilis MTCC 121 (BS 121) (to understand the interaction between micro-organisms & the modified surface). Biodegradation through the indoor soil burial method was assessed by measuring the change in tensile properties and growth of soil micro flora on the surface using optical light microscopy. Biodegradation by BS 121 was assessed by measuring the increase in its number along with the changes it brought about on the sample surface using optical light microscopy and SEM. It was observed that there was a reduction in the adhesion of soil flora and reduced growth of BS121 on ppTEOS coated CSPCL films. Thus ppTEOS coated CSPCL films seem to be an attractive option for environmentally benign packaging applications.

Preparation and Performance Characterization of Soft Polymer Composites as a Function of Single and Mixed Nano Entities

Soft polymer composite (SPC) was prepared by mixing a polyvinyl alcohol (PVA) host system with conducting carbon black (CCB) as a single nano entity (SNE) and CCB+Montmorillonite (MMT) clay as mixed nano entities (MNE). The modified crystalline phase to amorphous exhibits the impact of filler. The destroyed crystalline phases are also evident from XRD spectra where interplanar distance decreased. Addition of MNE resulted in inhibition of foreign bond formation and also prevented stretching and bending of substrate molecules, which were detected by Fourier Transform Infrared (FTIR) spectroscopy. The morphology of SPC was studied by optical and scanning electron microscopy (SEM). Improvement of glass transition temperature (Tg), Youngs modulus and AC conductivity was observed as a function of SNE and MNE loading.

Plasma Surface Modification of Biomaterials for Biomedical Applications

Application oriented selection of a material depends on the bulk properties of that material. However, a first encountering feature of any material in an application is its surface and thus material’s surface is one of the foremost parameter that decides the fate of material performance. Modulating the surface properties is considered as a potential approach to meet the application requirement. In past, various techniques (like, chemical, γ-irradiation, mechanical abrasion) have been developed for the surface modification of materials. These methods have certain disadvantages, like chemical treatment involve the disposal of polluted solvents/water in the environment, whereas other techniques may affect bulk properties of the material. Since three decades, plasma surface modification technique has attracted attention of scientists and technologists for creating new surfaces for various end-use applications such as textiles, food packaging, coatings, medical devices etc. Especially, low temperature plasma (low pressure and atmospheric pressure glow discharge) has attracted for its potential application in the new biomedical devices and biomaterials development. Plasma processing has proved itself a very promising and potent technology for modification of surface properties in an effective, environment friendly and economical way for converting low cost materials into a value added materials. The surface properties and biocompatibility can be enhanced selectively and precisely without affecting material’s bulk properties by the use of plasma surface modification technique. This chapter is providing a brief overview of low temperature plasma as a versatile technology for surface modification and its application pertaining to biomedical materials research. Various inferences are also drawn from the types of plasma used in the biomedical applications.

Influence of non-thermal TiCl4/Ar + O2 plasma-assisted TiOx based coatings on the surface of polypropylene (PP) films for the tailoring of surface properties and cytocompatibility

The superior bulk properties (corrosion resistance, high strength to weight ratio, relatively low cost and easy processing) of hydrocarbon based polymers such as polypropylene (PP) have contributed significantly to the development of new biomedical applications such as artificial organs and cell scaffolds. However, low cell affinity is one of the main draw backs for PP due to its poor surface properties. In tissue engineering, physico-chemical surface properties such as hydrophilicity, polar functional groups, surface charge and morphology play a crucial role to enrich the cell proliferation and adhesion. In this present investigation TiOx based biocompatible coatings were developed on the surface of PP films via DC excited glow discharge plasma, using TiCl4/Ar+O2 gas mixture as a precursor. Various TiOx-based coatings are deposited on the surface of PP films as a function of discharge power. The changes in hydrophilicity of the TiOx/PP film surfaces were studied using contact angle analysis and surface energy calculations by Fowkes approximation. X-ray photo-electron spectroscopy (XPS) was used to investigate the surface chemical composition of TiOx/PP films. The surface morphology of the obtained TiOx/PP films was investigated by scanning electron and transmission electron microscopy (SEM &TEM). Moreover, the surface topography of the material was analyzed by atomic force microscopy (AFM). The cytocompatibility of the TiOx/PP films was investigated via in vitro analysis (cell viability, adhesion and cytotoxicity) using NIH3T3 (mouse embryonic fibroblast) cells. Furthermore the antibacterial activities of TiOx/PP films were also evaluated against two distinct bacterial models namely Gram positive Staphylococcus aureus (S.aureus) and Gram negative Escherichia coli DH5α. (E.coli) bacteria. XPS results clearly indicate the successful incorporation of TiOx and oxygen containing polar functional groups on the surface of plasma treated PP films. Moreover the surface of modified PP films exhibited nano structured morphology, as confirmed by SEM, TEM and AFM. The physico-chemical changes have improved the hydrophilicity of the PP films. The in-vitro analysis clearly confirms that the TiOx coated PP films performs as good as the standard tissue culture plates and also are unlikely to impact the bacterial cell viability.

Evaluation of surface properties of low density polyethylene (LDPE) films tailored by atmospheric pressure non-thermal plasma (APNTP) assisted co-polymerization and immobilization of chitosan for improvement of antifouling properties

This work describes the development of antifouling functional coatings on the surface of low density polyethylene (LDPE) films by means of atmospheric pressure non-thermal plasma (APNTP) assisted copolymerization using a mixture of acrylic acid and poly (ethylene glycol). The aim of the study was to investigate the antifouling properties of the plasma copolymerized LDPE films and the same was carried out as a function of deposition time with fixed applied potential of 14 kV. In a second stage, the plasma copolymerized LDPE films were functionalized with chitosan (CHT) to further enhance its antifouling properties. The surface hydrophilicity, structural, topographical and chemistry of the plasma copolymerized LDPE films were examined by contact angle (CA), X-ray diffraction (XRD), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Coating stability was also studied in detail over a storage time of 15 days by storing in water and air. The antifouling properties of the plasma copolymerized LDPE films were examined via protein adsorption and platelet adhesion studies. CA study showed significant changes in surface wettability after the coating process. XPS and FTIR analysis proved the presence of a dense multifunctional coating and an efficient immobilization of CHT. Substantial amendments in surface topography were observed, positively enhancing the overall surface hydrophilicity. Finally, in-vitro analysis showed excellent antifouling behavior of the surface modified LDPE films.