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Borthakur L.J.,Nowgong College | Das D.,Tezpur University | Dolui S.K.,Tezpur University
Materials Chemistry and Physics | Year: 2010

Encapsulation of inorganic nano particles (as a core) by polymers (as a shell) is one of the interesting research subjects that lead to the synthesis of nano composite. Some of the preparative methods for the synthesis of nano composite are dispersion, suspension, emulsion and mini-emulsion polymerization techniques. Here core-shell nano composite particles of poly (styrene-co-methyl acrylate) and bentonite (modified with octadecyl amine) were prepared by mini-emulsion polymerization. The mini-emulsions were prepared by dispersing bentonite in the monomers mixture (styrene and methyl acrylate) in the presence of sodium dodecyl benzene sulfate (SDBS) and Span-60 as surfactants and hexadecane as costabilizer using ultra sonication. The stability of both mini-emulsion and the obtained latex depends on premixing procedures, time of ultrasonication, and more importantly on the applied surfactants. The encapsulation of the nano clay was confirmed by FTIR and XRD analysis. The morphology of the nano composite particles was determined by SEM and TEM analysis. TGA analysis of the composite particles shows that they exhibit better thermal stability as compared to the pristine polymer. © 2010 Elsevier B.V. All rights reserved.


Borthakur L.J.,Nowgong College | Konwer S.,Tezpur University | Das R.,Tezpur University | Dolui S.K.,Tezpur University
Journal of Polymer Research | Year: 2011

A series of nearly monodispersed poly(styrene- methyl acrylate) (SMA) copolymer latex particles were coated with polypyrrole having different graphite contents. The composite particles were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Xray diffraction (XRD) and thermogravimetric analysis (TGA). The d.c. conductivity and the electrochemical behaviour of the particles were studied by using a standard four-probe method and a cyclic voltameter respectively. The dependence of electrical conductivity of the composites on the concentration of graphite in the polypyrrole shell, the methyl acrylate content in SMA copolymer and the temperature was also investigated. The electrical conductivity of the samples can be tuned by varying the graphite content in the polypyrrole shell phase. The d.c. conductivity decreases with increasing methyl acrylate content in the core particles. Electrochemical study (at a scan rate of 50 mV s-1) reveals that the particles are sufficiently stable under redox potential and should find potential applications in various optoelectronic devices. © 2010 Springer Science+Business Media B.V.


Borthakur L.J.,Nowgong College | Sharma S.,Tezpur University | Dolui S.K.,Tezpur University
Journal of Materials Science: Materials in Electronics | Year: 2011

The colloidal dispersion of silver nano particles with different concentration (0.5, 1.0 and 1.5%) were synthesized by chemical reduction method using citrate as reducing agent. Colloidal dispersion of Poly (Styrene-co-methylacrylate) (SMA) was synthesized by mini emulsion polymerization technique. The SMA micro particles were used as template for the polymerization of pyrrole in presence of dispersion of silver nano particles by oxidative coupling method. The Ag nano particles and the final core-shell composite particles were characterized by UV-visible, FTIR, SEM, EDX and TEM analysis. The thermal analysis revealed that the SMA-PPy-Ag core-shell particles possesses better thermal stability in comparision with bare PPy-Ag nano composite. The dc conductivity and the electro chemical behaviour of the particles were studied by using a standard four-probe method. The dependence of electrical conductivity of the composites on the concentration of silver in the polypyrrole shell and the methyl acrylate content in SMA copolymer were also investigated The core-shell particles show reversible electrochemical response as revealed by the cyclic voltammetry study. © 2010 Springer Science+Business Media, LLC.


Borthakur L.J.,Nowgong College | Jana T.,Tezpur University | Dolui S.K.,Tezpur University
Journal of Coatings Technology Research | Year: 2010

A series of core-shell polymeric particles with poly(n-butyl acrylate-co-methacrylic acid-co-ethylene glycol dimethylacrylate) as core and poly(styrene-co-methyl methacrylate) as shell were prepared by seeded emulsion polymerization. The role of ethylene glycol dimethylacrylate (EGDMA) is to crosslink the core so as to avoid any probability of gel formation and to bind both the core and the shell phase together. The spherical morphology of the core-shell structure was achieved at 60:40 core to shell ratio. The core-shell morphology was confirmed by SEM and TEM analyses. GPC analysis of the particles reveals that the polymer shows a bimodal mode. The first peak has M w = 382700 and M n = 245200 with polydispersity index of 1.6, and the second peak has M w = 21200 and M n = 14800 with polydispersity index of 1.4. These core-shell latexes were applied as a pigment/binder in emulsion paint and the paint properties like gloss, rock hardness, washability, opacity, etc. were compared with the standard. The results show that these core-shell latexes can provide similar hiding power with 17% reduction of TiO 2 in the paint formulation. © 2010 FSCT and OCCA.


Konwer S.,Tezpur University | Barthakur L.J.,Nowgong College | Dolui S.K.,Tezpur University
Journal of Materials Science: Materials in Electronics | Year: 2012

A series of core-shell particles (SMAP/G) having polystyrene-methylacrylate copolymer (styrenemethyl acrylate) as the core and graphite incorporated polyaniline as the shell were prepared by surfactant free mini-emulsion polymerization. Here poly (SMA) copolymer latex particles were first dispersed in water and then coated with polyaniline (PA) by in situ polymerization of aniline in presence of different percentage (0.25, 0.50 and 1.0%) of graphite. The composite particles were characterized by FTIR, XRD and TGA. TEM and SEM analysis confirms the core-shell morphology of the composite particles. DC electrical conductivity values of all the samples were measured by using a standard four-probe method. The effect of temperature and the amount of graphite incorporated into the PA shell on the dc electrical conductivity of the core-shell composites was investigated. The electro chemical behaviour of the core-shell composites was studied by using a cyclic voltammeter. Electro chemical data shows that the core-shell composites are sufficiently stable under redox potential of 50 mV/s to find applications in various electronic devices. © Springer Science+Business Media, LLC 2011.

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