Sandip Maiti

A strategy to achieve high electromagnetic interference shielding and ultra low percolation in multiwall carbon nanotube–polycarbonate composites through selective localization of carbon nanotubes

Here, we report a simple method that involves solution blending of polycarbonate (PC) in the presence of multiwall carbon nanotubes (MWCNTs) and commercial PC beads for the preparation of electrically conducting MWCNT–PC composites with high electromagnetic interference shielding effectiveness (EMI SE) and electrical conductivity at very low (∼0.021 wt%) percolation threshold (pc). Thus, electrical conductivity of ∼4.57 × 10−3 S cm−1 was achieved in the MWCNT–PC composites at an extremely low MWCNT loading (0.10 wt%) in the presence of 70 wt% PC beads in the composites. Finally, optimizing the ratio of PC beads and MWCNT loading in the composites, a very high EMI SE value (∼23.1 dB) was achieved at low loading (2 wt%) of MWCNT with 70 wt% PC beads. The effective concentration of MWCNT increases in the solution blended PC region with increasing the amount of PC beads. Thus, a strong interconnected conductive network structure of CNT–CNT is developed throughout the matrix and the presence of strong π–π interaction among the electron-rich phenyl rings of PC and MWCNT in the composites plays a crucial role in increasing the EMI shielding value and electrical conductivity of the MWCNT–PC composites.

Compatibilization Mechanism of Nanoclay in Immiscible PS/PMMA Blend Using Unmodified Nanoclay

Organically modified nanoclays have been reported to play the role of a compatibilizer for immiscible polymer blends. However, the mechanism of compatibilization by nanoclay has been reported differently. In this work, we investigated the exact mechanism of compatibilization of nanoclay in immiscible polystyrene (PS)/poly(methyl methacrylate) (PMMA) blend in the presence of sodium-montmorillonite (Na-MMT) through selective dispersion of clay in the matrix phase. Through a detailed investigation of the morphology of PS/PMMA/Na-MMT blend nanocomposites, the plausible mechanism behind the compatibilization effect of clay in immiscible blends has been proposed.

Electrochemical and electrical performances of cobalt chloride (CoCl2) doped polyaniline (PANI)/graphene nanoplate (GNP) composite

The present study represents a simple and scalable method that involves in situ polymerization of cobalt chloride (CoCl2·6H2O) doped aniline in the presence of graphene nanoplates (GNPs) in HCl medium, for the preparation of CoCl2 doped polyaniline (PANI)/GNP composites (PGC) as a supercapacitor electrode material with noteworthy performance. The maximum specific capacitance and energy density of the PGC composites were found to be ≈634 F g−1 and ≈427 W h kg−1, respectively, at a 10 mV s−1 scan rate. Through judicious control of the GNP content and CoCl2 doped PANI in the composites, a very high electrical conductivity (≈12.2 S cm−1) was achieved at unprecedented low GNP content. The PGC composites also exhibited high alternating current (AC) electrical conductivity in the frequency region of ∼101 to ∼107 Hz. The morphology of the composites was successfully studied by field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM).

An approach to reduce the percolation threshold of MWCNT in ABS/MWCNT nanocomposites through selective distribution of CNT in ABS matrix

In this article, we demonstrate a facile route to prepare ABS/MWCNT nanocomposites with high electrical conductivity at a significantly low percolation threshold of the CNT. The strategy involves in situ co-polymerization of styrene and acrylonitrile monomers in the presence of multi-wall carbon nanotubes (MWCNT) and commercially available acrylonitrile butadiene styrene (ABS) beads. A dramatic improvement in the electrical conductivity in the nanocomposites was evident with increasing content of ABS beads at a constant CNT loading, which might be explained in terms of the formation of a continuous network structure of CNTs throughout the in situ polymerized ABS matrix. Such selective dispersion of MWCNTs results in an electrical conductivity (3.01 × 10−7 S cm−1) in the nanocomposites at 30 vol% loading of ABS beads and 0.24 vol% loading of MWCNTs. An increase in electrical conductivity to 4.50 × 10−5 S cm−1 was evident when the ABS bead content was increased to 60 vol% at the same loading of MWCNTs. The morphological analysis of the nanocomposites indicates selective distribution of the MWCNTs in the in situ co-polymerized ABS phase of the nanocomposites leaving the externally added ABS beads free from CNT dispersion. This leads to an increase in effective concentration of the CNTs in the in situ co-polymerized ABS phase of the nanocomposites, which in turn creates a path of MWCNTs throughout the matrix, resulting in a decrease in the percolation threshold of the nanocomposites to a lower value (0.2 vol% MWCNT).

Grafting of poly(vinyl chloride) with methyl methacrylate—I. Synthesis and characterization

Abstract Poly(vinyl chloride) was first dehydrochlorinated in an alkaline medium and then grafted with methyl methacrylate using benzoyl peroxide as free radical initiator in an inert atmosphere. Studies were carried out to determine the effects on grafting of synthesis conditions such as time, initiator concentration, ratio of monomer to polymer, dehydrochlorination at various temperatures and solvent concentration. A maximum of 33% grafting was obtained for the optimum set of conditions. Percentage graft and grafting efficiency were determined from chlorine contents of the grafted products.

Grafting of poly(vinyl chloride) with methyl methacrylate—II. Thermal and mechanical behaviour

Abstract Graft copolymers of poly(vinyl chloride) with poly(methyl methacrylate) were initially characterized by i.r. spectroscopy; absorption bands corresponding to carbonyl peaks (1744 cm−1) showed a linear increase with the increase in the percentage of grafts. Uniformity of grafts in each case was represented by single transitions which correspond to Tg for that sample. Thermogravimetric analysis has shown a marked improvement in thermal stability as graft content increased. Intrinsic viscosity data showed increase in viscosity with increasing graft content. Stress/strain studies showed an increase in yield stress and initial modulus but a decrease in yield strain and percentage elongation with increase in graft content.