Tanya Das

Graphene decorated with hexagonal shaped M-type ferrite and polyaniline wrapper: a potential candidate for electromagnetic wave absorbing and energy storage device applications

The development of promising microwave absorbing materials is a booming field of research in both the commercial and defense sectors to prevent electromagnetic pollution, and also to enrich the field of stealth technology. Supercapacitors are a symbol of clean energy storage devices. The present work attends to the preparation of hexagonal shaped magnetic M-type hexaferrite, CuFe10Al2O19 (CFA) by a facile chemical co-precipitation method, and the formation of its composites (graphene/CFA) in the presence of acid modified graphene. An in situ approach was employed for the coating of graphene with CFA. Another nanocomposite (graphene/CFA/PANI) was prepared by the wrapping of graphene/CFA with polyaniline (PANI), which was prepared through the in situ chemical oxidation polymerization of aniline. The prepared multifunctional nanocomposites showed an outstanding and improved microwave absorption property (the maximum reflection loss was −63.6 dB at a thickness of 2.5 mm with a broad absorption range) and electrochemical properties (the highest specific capacitance value was 342 F g−1), in contrast to the pristine graphene and CFA. The addition of PANI also improves the microwave absorption and specific capacitance of the nanocomposites. The formation of the multifunctional nanocomposites and their structural characteristics are discussed thoroughly with their impact on the two different fields of applications i.e. microwave absorbing and energy storage device applications individually.

Specific functionalization and polymer grafting on multiwalled carbon nanotubes to fabricate advanced nylon 12 composites

This paper deals with polymer grafting of multi-walled carbon nanotubes (MWCNTs) via ultraviolet/ozone (UV/O3) assisted polymer grafting (UVOG) in order to improve the filler efficiency and thus giving a highly homogeneous dispersion, strong filler–matrix interactions and excellent distribution of individual nanotubes in the polymer matrix. Though several chemical procedures of grafting have been developed to obtain dispersible CNTs, grafting by a fast, low cost, non hazardous and controllable process is still under active research. 2-Acrylamido-2-methylpropane sulfonic acid (AMPS) monomers were employed for grafting onto MWCNTs due to their very hydrophilic and reactive sulfonic (SO3H) end groups. The structural and morphological changes in poly-AMPS grafted MWCNTs (PAG-MWCNTs) were characterized by FTIR spectroscopy, XPS, Raman spectroscopy, TEM and FESEM. When the PAG-MWCNTs were incorporated into nylon 12, the results showed excellent uniform dispersion of individual MWCNTs throughout the matrix and improved the mechanical properties of the composites. Addition of only 0.75 wt% PAG-MWCNTs showed an improvement of tensile strength and Youngs modulus by ∼43% and 33%, respectively, compared with those of neat nylon 12. Moreover, the PAG-MWCNTs/nylon 12 composites exhibited a ∼12 °C improvement in the glass transition temperature (Tg) compared to the raw MWCNTs/nylon 12 composites. From a literature survey, these results are found to be quite promising. Therefore, we believe that the polymer grafting of MWCNTs presented herein will be a useful technique to produce novel filler materials for preparing various advanced nanocomposites. Moreover, this grafting technique may also be employed to introduce other functional polymers onto the surface of MWCNTs.

Enhanced Molecular Level Dispersion and Interface Bonding at Low Loading of Modified Graphene Oxide To Fabricate Super Nylon 12 Composites

Development of advanced graphene based polymer composites is still confronted with severe challenges due to its poor dispersion caused by restacking, weak interface bonding, and incompatibility with polymer matrices which suppress exertion of the actual potential of graphene sheets in composites. Here, we have demonstrated an efficient chemical modification process with polyethylenimine (PEI) to functionalize graphene oxide which can overcome the above-mentioned drawbacks and also can remarkably increase the overall strength of the nylon 12 composites even at very low graphene loading. Chemical modification was analyzed by various surface characterizations including X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. Addition of only 0.25 and 0.35 wt % modified GO showed 37% and 54% improvement in tensile strength and 65% and 74% in Youngs modulus, respectively, compared with that of the neat polymer. The dynamic mechanical analysis showed ∼39% and 63% increment in storage modulus of the nanocomposites. Moreover, the nanocomposites exhibited significantly high thermal stability (∼15 °C increment by only 0.35 wt %) as compared to neat polymer. Furthermore, the composites rendered outstanding resistance against various chemicals.

Improved Polymer Encapsulation on Multiwalled Carbon Nanotubes by Selective Plasma Induced Controlled Polymer Grafting

Surface graft polymerization on multiwalled carbon nanotubes (MWCNTs) with several grafting mechanisms is nowadays a demanding field of nanocomposites in order to enhance the load carrying capacity, thus improving the overall performance of the composites. Here, we demonstrate the covalent grafting of a sulfonic acid terminated monomer, 2-acrylamido-2-methylpropane sulfonic acid onto sidewalls of MWCNTs via a comparative study between oxygen plasma induced grafting (OPIG), nitrogen plasma induced grafting (NPIG), and nitrogen + oxygen plasma induced grafting (NOPIG) with the aim to identify the most effective process for the preparation of polymer encapsulated carbon nanotubes. From the detail surface analysis, it has been noticed that NOPIG offered much better surface grafting than that of the OPIG and NPIG. The transmission electron microscopy (TEM) images showed that MWCNTs modified by NOPIG possess much thicker and uniform polymer coatings throughout. From thermogravimetric analysis (TGA), the grafting degree was found to be ~80 wt % for the NOPIG sample.

High performance of cyclic olefin copolymer-based capillary electrophoretic chips.

This paper demonstrates a simple, one step, and low cost surface modification technique for producing cyclic olefin copolymer (COC) polymer-based microcapillary electrophoresis chips consisting highly hemocompatible microchannels by UV-photografting with N-vinylpyrrolidone (NVP) monomer. An optimal condition has been identified to achieve the best surface grafting process. It has been found that this surface treatment enables extremely high surface wettability, hemocompatibility, and bond strength to the microchannels. The surface grafting was confirmed by attenuated total reflection Fourier transform-infrared spectroscopic (ATR-FTIR) study. In vitro protein adsorption using fluorescent labeled bovine serum albumin (FITC-BSA) into the COC microchannel results indicates that the modified chips have excellent protein resistance ability because of the increase of surface hydrophilicity. Hence, the modified chips showed fast, reproducible and high efficient separations of proteins (up to 51,000 theoretical plates per meter). Moreover, this surface modification process show no loss in the optical transparency to the modified microchannel surfaces: an important requirement for real capillary electrophoresis since the fluorescent intensity is directly related to the amount of adsorbed protein on the surface. Therefore, we believe that this simple and promising route of surface modification could be very useful for developing high performance COC microfluidic devices for the separation of proteins, amino acids, and other biomolecules.

A green technique to prepare uniform amine capped multi-walled carbon nanotubes to fabricate high strength, protein resistant polymer nanocomposites

An effort has been made to produce efficient amino functionalized carbon nanotubes (CNTs) without utilizing any hazardous chemicals, with an aim to use them in biomaterials as well as in advanced polymer nanocomposites. Because it is water soluble, biocompatible and rich in primary amines, allylamine (AA) was selected for surface functionalization. Grafting was performed by a novel approach, i.e. double UV-ozone induced grafting (DUVO) process, which is absolutely eco-friendly, fast, cost-effective and highly controllable. Optimized conditions have been identified to achieve the highest degree of grafting with uniform thickness. To explore their functionality, the PAA-g-MWCNTs were incorporated into Nylon 6 and PET matrices; remarkable increases in tensile strength (34% and 78%) and Youngs modulus (44% and 30%) at only 0.3 wt% filler loading were noticed due to excellent dispersion and strong adhesion with the polymer matrix. Moreover, in vitro BSA and Fb protein adsorption tests showed that the nanocomposites containing PAA-g-MWCNTs possess significantly higher surface antifouling property as compared to the neat polymers. It was also interesting to note that the antifouling property of the composites increased with increasing polymer grafting density on the CNTs. These results clearly suggest that the DUVO-PAA-g-MWCNTs would be versatile novel filler materials in the field of advanced polymer nanocomposites as well as in biomaterials.

Heat sensing Thermoplastic Elastomer Based on Polyolefins for Encapsulation Applications

Use of Thermoplastic Elastomers (TPEs) has become a unique pathway to meet the daily requirements of various applications. The ease of using TPEs lies in the fact that they pro‐ vide both the character of the individual properties as they are constructional polymers, which are physically crosslinked materials made up of a thermoplastic and an elastomer. There are several TPE’s in market and individual have several outstanding performances. Out of several researches, our aim in this article is to focus on the influence of Polyolefin based TPE’s. This paper focusses on the different aspects of TPO’s their physical, chemi‐ cal, mechanical, and electrical characteristics, advantages and uses of these materials along with a particular focus on their use in encapsulation application. Factors that could affect the end use are also explained here in details. Heat shrinkability test, cure time, and SEM are some of the characterisations used to demonstrate the exact criteria of polyolefin based TPE’s for encapsulation application.

Liquid Crystalline Polymer and Its Composites: Chemistry and Recent Advances

The high strength and stiffness of Liquid Crystalline polymers (LCPs) are due to their rigid rod-like molecules which forms a highly ordered structures that result in self-reinforcing characteristics. Thermotropic LCPs exhibit exceptional mechanical properties when oriented. Commercial LCP resins are often filled with glass or other types of fillers like silica, clay, carbon nanotubes, graphene, and halloysite nanotube type fillers to negate the anisotropy and to reduce the cost.