Qualification: 
Ph.D, MSc
gnk_swamy@blr.amrita. edu
Phone: 
+91-9886883788

Dr. Kumaraswamy G. N. currently serves as Chairperson and  Associate Professor at the Department of Physics, Amrita School of Engineering, Bengaluru campus. He pursued his M.Sc. from University of Mysore in 2002 and Ph. D. from University of Mysore in 2007.

Publications

Publication Type: Journal Article

Year of Publication Publication Type Title

2017

Journal Article

K. V. Aneesh Kumar, Kumaraswamy, G. N., Ranganathaiah, C., and Ravikumar, H. B., “Influence of oxygen ion implantation on the free volume parameters and electrical conductivity of a polymer-based bakelite RPC detector material”, Journal of Applied Polymer Science, vol. 134, 2017.[Abstract]


We have investigated the effect of ion implantation on structural modification and the electrical conductivity of Bakelite-resistive plate chamber (RPC) detector material used in high energy physics experiments. Samples of Bakelite polymer were exposed to 100 keV and 150 keV oxygen ions in the fluence of 1012 to 1015 ions cm−2. Ion implantation induced microstructural changes have been studied using positron annihilation lifetime spectroscopy, X-ray diffraction and Fourier transform infrared techniques. Positron lifetime parameters viz., o-Ps lifetime and its intensity showed formation of radicals, secondary ions due to the creation of interior tracks by high-energy ions followed by chain scission at lower fluence of 100 keV implantation. The decreased free volume size at 150 keV ion implantation is an indication of crosslinking and filling up of interior tracks by the implanted ions. Variation of ac conductivity with frequency obeys Jonscher power law at 100 keV and the conduction mechanism is explained by barrier hopping model. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44962. © 2017 Wiley Periodicals, Inc.

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2009

Journal Article

C. Ranganathaiah and Kumaraswamy, G. N., “New method of determining miscibility in binary polymer blends through hydrodynamic interaction: The free volume approach”, Journal of Applied Polymer Science, vol. 111, pp. 577–588, 2009.[Abstract]


A new method has been developed to determine the probability of miscibility in binary polymer blends through hydrodynamic interaction. This is achieved by the measurement of the free volume content in blends of carefully selected systems—styrene acrylonitrile (SAN)/poly(methyl methacrylate) (PMMA), PMMA/poly(vinyl chloride) (PVC), and PVC/polystyrene (PS)—with positron annihilation lifetime spectroscopy. The free volume content can predict the miscible/immiscible nature of the blends but provides no information on the extent of miscibility for different compositions of the blends. We have generalized a model used to understand the viscometric behavior of polymer/solvent systems to polymer/polymer systems through the free volume approach. This model provides two important parameters: a geometric factor (γ) and a hydrodynamic interaction parameter (α). γ depends on the molecular architecture, whereas α accounts for the excess friction at the interface between the constituents of the blend, and we propose that α can serve as a precursor to miscibility in a system and indicate which composition produces a high probability of miscibility. The efficacy of this proposition has been checked with measured free volume data for the three blend systems. The SAN/PMMA system produces a maximum α value of −209 at 20% PMMA; PVC/PMMA produces a maximum α value of −57 at 10% PMMA. Interestingly, for the PS/PVC system, α is close to zero throughout the entire concentration range. Therefore, we infer that α is perhaps an appropriate parameter for determining the composition-dependent probability of miscibility in binary blend systems. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 More »»

2009

Journal Article

C. Ranganathaiah and Kumaraswamy, G. N., “Experimental evaluation of hydrodynamic interaction parameter as a precursor to polymer/polymer miscibility: a free volume approach”, J. Appl. Polym. Sci. , 2009.

2007

Journal Article

R. F. Bhajantri, Ravindrachary, V., Harisha, A., Ranganathaiah, C., and Kumaraswamy, G. N., “Effect of barium chloride doping on PVA microstructure: positron annihilation study”, Applied Physics A, vol. 87, pp. 797–805, 2007.[Abstract]


Microstructural studies on BaCl2 doped polyvinyl alcohol (PVA) polymer films were carried out using density, PAL and dielectric measurements at room temperature. The positron annihilation studies on these samples shows considerable effect on the PVA microstructure due to doping and is understood by invoking the chemical reaction between Ba2+ ions of BaCl2 with OH groups of PVA via intra/inter molecular hydrogen bonding, which forms the complex. This complex formation modifies the free volume content in the amorphous fraction, and results in an enhancement of the polymer crystallinity. At higher dopant concentrations, the number of such complexes increases, and ends up with the formation of dopant aggregates or agglomerates leading to certain phase separation into a polymer-rich phase and a dopant-rich phase. These phase separations are thought to be due to the existence of two or more crystalline phases within the polymer matrix. The XRD study also supports this enhancement of PVA crystallinity due to doping. The electrical studies on the doped PVA reflects that the complex formation due to doping affects the microstructure and hence the dielectric properties including the dc and ac conductivities of the polymer. All of these observed results were analyzed and understood based on the microstructural modification of PVA as a function of dopant concentrations. More »»

2007

Journal Article

A. K. Subramani, Byrappa, K., Kumaraswamy, G. N., Ravikumar, H. B., Ranganathaiah, C., Rai, K. M. Lokanatha, Ananda, S., and Yoshimura, M., “Hydrothermal preparation and characterization of TiO2:AC composites”, Materials Letters, vol. 61, pp. 4828 - 4831, 2007.[Abstract]


A new photocatalyst titania:activated carbon (TiO2:AC) composite was prepared by impregnating anatase type TiO2 nanoparticulates onto the activated carbon surface through a mild hydrothermal route. A varied ratio of TiO2 to \{AC\} was considered for impregnation. As-prepared TiO2:AC composite was characterized by various techniques such as powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), \{BET\} surface area and positron annihilation lifetime spectroscopy (PALS). Powder \{XRD\} results showed the persisting nature of anatase phase of TiO2 deposited on the activated carbon surface. The BET, \{FTIR\} and \{PALS\} results revealed the impregnation threshold. The TiO2 particulates were well adhered and uniformly dispersed on the carbon surface as confirmed by SEM. More »»

2006

Journal Article

G. N. Kumaraswamy, Ranganathaiah, C., Urs, M. V. Deepa, and Ravikumar, H. B., “Miscibility and phase separation in SAN/PMMA blends investigated by positron lifetime measurements”, European Polymer Journal, vol. 42, pp. 2655 - 2666, 2006.[Abstract]


Miscibility and phase separation in SAN/PMMA blends have been investigated using DSC, İR\} spectroscopy and positron lifetime spectroscopy (PLS). Single broad glass transition observed throughout the blend compositions, may be due to overlap of two glass transitions. İR\} measurements clearly indicate the absence of strong interactions. This supports miscibility is due to intramolecular repulsive forces in the \{SAN\} component. On the other hand, free volume data show negative deviation from linear additivity indicating the blends are miscible. The interchain interaction parameter β exhibits a complex behavior and the extent of miscibility is not revealed. Following Wolf’s treatment, we have evaluated the geometry factor γ and hydrodynamic interaction parameter α and found α is a suitable parameter in predicting the miscibility window. The cloud points in SAN/PMMA blends increase with decreasing \{PMMA\} content. The change in free volume size correlates well with the observed change in cloud point. More »»

2006

Journal Article

B. G. Soares, Almeida, M. S. M., Urs, M. V. Deepa, Kumaraswamy, G. N., Ranganathaiah, C., ,, and Mauler, R., “Influence of curing agent and compatibilizer on the physicomechanical properties of polypropylene/nitrile butadiene rubber blends investigated by positron annihilation lifetime technique”, Journal of Applied Polymer Science, vol. 102, pp. 4672–4681, 2006.[Abstract]


A series of thermoplastic vulcanizates of polypropylene (PP)/nitrile butadiene rubber (NBR) (50/50) have been prepared by melt-mixing method, using phenolic resin/SnCl2 as the curing system and maleic anhydride-functionalized PP (PP-g-MA) and carboxylated NBR (NBRE-RCOOH) as the compatibilizing system. Triethylenetetramine was also employed to promote the reaction between the functionalized polymers. The effects of curing agent and compatibilizer on the mechanical and morphological properties have been studied. A novel technique based on positron annihilation lifetime spectroscopy has been used to measure the free volume parameters of these systems. The positron results showed minimum free volume size and free volume fraction at 5.0% of the curing agent suggesting some crosslinking in the rubber phase. The reduction in free volume holes at 2.5% of the compatibilizer is interpreted as improvement in the interfacial adhesion between the components of the blend. The observed variation of free volume fraction is opposite to the tensile strength and exhibits the correlation that, lesser the free volume more is the tensile strength at 2.5% of the compatibilizer in the blend. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4672–4681, 2006. More »»

2006

Journal Article

G. N. Kumaraswamy and Ranganathaiah, C., “Free volume microprobe studies on poly(methyl methacrylate)/poly(vinyl chloride) and poly(vinyl chloride)/polystyrene blends”, Polymer Engineering & Science, vol. 46, pp. 1231–1241, 2006.[Abstract]


Blends of Poly(methyl methacrylate) (PMMA)/Poly(vinyl chloride) (PVC) and Poly(vinyl chloride) (PVC)/Polystyrene (PS) of different compositions were prepared by solution casting technique. The blends were characterized using Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), and Positron Lifetime Spectroscopy. DSC data were found to be inadequate to describe whether PMMA/PVC blends are miscible or not, possibly because of the small gap in their glass transition temperatures. On the other hand, PVC/PS blends were clearly found to be immiscible by DSC. FTIR results for PMMA/PVC indicate the possible interactions between the carbonyl group of PMMA and α-hydrogen of PVC. Free volume data derived from Positron lifetime measurements showed that the PMMA/PVC blends to be miscible in low PVC concentration domain. For the first time, the authors have evaluated the hydrodynamic interaction parameter α, advocated by Wolf and Schnell, Polymer, 42, 8599 (2001), to take into account the friction between the component molecules using the free volume data. This parameter (α) has a high value (−57) at 10 wt% of PVC, which could be taken to read miscibility for PMMA/PVC blends to be high. In the case of PVC/PS blends, the positron results fully support the DSC data to conclude the blends to be immiscible throughout the range of concentration. As expected, the hydrodynamic interaction parameter α does not show any change throughout the concentration in PVC/PS blends, further supporting the idea that α is another suitable parameter in the miscibility study of polymer blends. POLYM. ENG. SCI., 46:1231–1241, 2006. © 2006 Society of Plastics Engineers More »»

2006

Journal Article

H. B. Ravikumar, Ranganathaiah, C., Kumaraswamy, G. N., Urs, M. V. Deepa, Jagannath, J. H., Bawa, A. S., and Thomas, S., “Differential scanning calorimetric and free volume study of reactive compatibilization by EPM-g-MA of poly(trimethylene terephthalate)/EPDM blends”, Journal of Applied Polymer Science, vol. 100, pp. 740–747, 2006.[Abstract]


Differential scanning calorimetry (DSC) and positron annihilation lifetime measurements have been carried out to study the effect of the compatibilizer maleic anhydride grafted ethylene propylene copolymer (EPM-g-MA) in poly trimethylene terephthalate and ethylene propylene diene monomer (PTT/EPDM) immiscible blends. The DSC results for the blends of 50/50 and 30/70 compositions show two clear glass transition temperatures, indicating that the blends are two-phase systems. With the addition of compatibilizer, the separation between the two glass transitions decreased, suggesting an increased interaction between the blend components with compatibilizer. At 5 wt % of compatibilizer, the separation between the Tgs reduced in both 50/50 and 30/70 blends. The positron results for the blends without compatibilizer showed an increase in relative fractional free volume, as the EPDM content in the blend is increased. This suggests the coalescence of free volume of EPDM with the free volumes of PTT due to phase separation. However, the effect of compatibilizer in the blends was clearly seen with the observed minimum in free volume parameters at 5% of the compatibilizer, further suggesting that this percent of compatibilizer seems to be the optimum value for these blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 740–747, 2006 More »»

2005

Journal Article

H. B. Ravikumar, Ranganathaiah, C., Kumaraswamy, G. N., and Thomas, S., “Positron annihilation and differential scanning calorimetric study of poly(trimethylene terephthalate)/EPDM blends”, Polymer, vol. 46, pp. 2372 - 2380, 2005.[Abstract]


The blends of poly(trimethylene terephthalate) (PTT) and ethylene propylene diene monomer (EPDM) with different composition have been studied by positron lifetime technique (PLT) and differential scanning calorimetric (DSC) measurements. The \{DSC\} results for the blends of 50/50 and 40/60 show clear two glass transition temperatures indicating two-phase system. No melting point depression was observed for the blend system, which strongly supports the incompatibility. From the positron results an increase in free volume hole size and its concentration has been observed with the increase in \{EPDM\} content of the blend which indicates further that there is coalescence of free volumes of \{EPDM\} with the \{PTT\} to some extent and phase separation behavior continues. Another interesting aspect is that the relative fractional free volume exhibits neither negative nor positive deviation from the log additivity rule. It agrees well with the log additivity rule. The interchain interaction parameter evaluated from these results show some complex behavior. \{XRD\} results show the decrease in crystallinity of the blend with the increase in fractional free volume with the increase in concentration of EPDM. More »»

2005

Journal Article

H. B. Ravikumar, Ranganathaiah, C., Kumaraswamy, G. N., and , “Influence of free volume on the mechanical properties of Epoxy/poly (methylmethacrylate) blends”, Journal of Materials Science, vol. 40, pp. 6523–6527, 2005.[Abstract]


Positron lifetime measurements have been performed to investigate the free volume dependence of the mechanical properties of Epoxy/poly methyl methacrylate (PMMA) blends of varying composition of PMMA (2.5, 5, 7.5, 10, 12.5, 15, and 17.5 wt{%}). The mechanical properties of the blends have been evaluated according to the (ASTM) standard. The positron results indicate that the mechanical properties like tensile strength and surface hardness have a significant dependence on the free volume of the blends. It is also found that the blends of the present study show positive deviation from the familiar linear additivity rule suggesting the immiscible nature of the blends. Further, up to 5-wt{%} of PMMA in the blend, an increase in relative fractional free volume correlates well with a decrease of tensile strength. More »»

2005

Journal Article

H. Kumar, ,, Kumaraswamy, G. N., Ravikumar, H. B., and Ranganathaiah, C., “Free volume and the physico-mechanical behaviour of polyurethane/polyacrylonitrile interpenetrating polymer networks: positron annihilation results”, Polymer International, vol. 54, pp. 1401–1407, 2005.[Abstract]


A series of semi-interpenetrating polymer networks (SIPNs) of polyurethane (PU) and polyacrylonitrile (PAN) in the weight ratios 90/10, 70/30, 60/40 and 50/50 PU/PAN were prepared using polyethylene glycol, 4,4′-diphenylmethane diisocyanate and acrylonitrile by sequential polymerization. Differential scanning calorimetry and scanning electron microscopy techniques were used to find the glass transition temperature and surface morphology of SIPNs. The tough and transparent SIPN films were characterized for physico-mechanical properties such as density, surface hardness and tensile properties. Positron annihilation lifetime spectroscopy (PALS) was used to measure the free volume behaviour of the IPNs. The sorption behaviour of IPNs with benzene penetrant was also measured. An attempt was made to correlate the PALS results with the mechanical and sorption properties of the SIPNs. Copyright © 2005 Society of Chemical Industry More »»

Publication Type: Conference Paper

Year of Publication Publication Type Title

2016

Conference Paper

Sa Shilpa, Venkatachalaiah, K. Nb, Damle, Rc, Kumar, Pd, Kanjilal, Dd, and Kumaraswamy, G. N., “Effect of low energy ion irradiation on the transport and structural behavior of PEDOT:PSS systems”, in AIP Conference Proceedings, 2016, vol. 1731.[Abstract]


In the past two decades, organic conductors have been widely explored for use in different applications. One of the extensively studied organic material for the use in the field of electronic devices is PEDOT:PSS. Organic/inorganic nanocomposite systems have been developed to improve the properties of organic materials. In the present study, we have made an attempt to understand the effect of low energy oxygen ion beam irradiation on the electrical and structural properties of PEDOT:PSS and PEDOT:PSS/TiO2 nanocomposites. The observed reduction in electrical properties in PEDOT:PSS systems may be linked to radiation induced phase change. The nanocomposite systems show better stability to the ion irradiation compared to the pure systems. © 2016 Author(s).

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2016

Conference Paper

H. Manjunatha, Damle, Rb, and Kumaraswamy, G. N., “Ion beam irradiation as a tool to improve the ionic conductivity in solid polymer electrolyte systems”, in AIP Conference Proceedings, 2016, vol. 1728.[Abstract]


Solid polymer electrolytes (SPEs) have potential applications in solid state electronic and energy devices. The optimum conductivity of SPEs required for such applications is about 10-1-10-3 Scm-1, which is hard to achieve in these systems. It is observed that ionic conductivity of SPEs continuously increase with increasing concentration of inorganic salt in the host polymer. However, there is a critical concentration of the salt beyond which the conductivity of SPEs decreases due to the formation of ion pairs. In the present study, solid polymer thin films based on poly (ethylene oxide) (PEO) complexed with NaBr salt with different concentrations have been prepared and the concentration at which ion pair formation occurs in PEOxNaBr is identified. The microstructure of the SPE with highest ionic conductivity is modified by irradiating it with low energy O+1 ion (100 keV) of different fluencies. It is observed that the ionic conductivity of irradiated SPEs increases by one order in magnitude. The increase in ionic conductivity may be attributed to the enhanced segmental motion of the polymer chains due to radiation induced micro structural modification.

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2016

Conference Paper

K. VaAneesh Kumar, Ranganathaiah, Cb, Kumaraswamy, G. N., and Ravikumar, H. Ba, “Oxygen ion implantation induced microstructural changes and electrical conductivity in Bakelite RPC detector material”, in AIP Conference Proceedings, 2016, vol. 1728.[Abstract]


In order to explore the structural modification induced electrical conductivity, samples of Bakelite Resistive Plate Chamber (RPC) detector materials were exposed to 100 keV Oxygen ion in the fluences of 1012, 1013, 1014 and 1015 ions/cm2. Ion implantation induced microstructural changes have been studied using Positron Annihilation Lifetime Spectroscopy (PALS) and X-Ray Diffraction (XRD) techniques. Positron lifetime parameters viz., o-Ps lifetime and its intensity shows the deposition of high energy interior track and chain scission leads to the formation of radicals, secondary ions and electrons at lower ion implantation fluences (1012 to1014 ions/cm2) followed by cross-linking at 1015 ions/cm2 fluence due to the radical reactions. The reduction in electrical conductivity of Bakelite detector material is correlated to the conducting pathways and cross-links in the polymer matrix. The appropriate implantation energy and fluence of Oxygen ion on polymer based Bakelite RPC detector material may reduce the leakage current, improves the efficiency, time resolution and thereby rectify the aging crisis of the RPC detectors. © 2016 Author(s). More »»

2014

Conference Paper

H. Manjunatha, Kumaraswamy, G. N., Damle, R., and , “Effect of low energy oxygen ion beam irradiation on ionic conductivity of solid polymer electrolyte”, in AIP Conference Proceedings, 2014.[Abstract]


Over the past three decades, solid polymer electrolytes (SPEs) have drawn significant attention of researchers due to their prospective commercial applications in high energy-density batteries, electrochemical sensors and super-capacitors.The optimum conductivity required for such applications is about 10-2 - 10-4 S/cm, which is hard to achieve in these systems.It is known that the increase in the concentration of salt in the host polymer results in a continuous increase in the ionic conductivity. However, there is a critical concentration of the salt beyond which the conductivity decreases due to formation of ion pairs with no net charge. In the present study, an attempt is made to identify the concentration at which ion pair formation occurs in PEO: RbBr. We have attempted to modify microstructure of the host polymer matrix by low energy ion (Oxygen ion, O+1 with energy 100 keV) irradiation. Ionic conductivity measurements in these systems were carried out using Impedance Spectroscopy before and after irradiation to different fluencies of the oxygen ion. It is observed that the conductivity increases by one order in magnitude. The increase in ionic conductivity may be attributed to the enhanced segmental motion of the polymer chains. The study reveals the importance of ion irradiation as an effective tool to enhance conductivity in SPEs.

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2009

Conference Paper

J. M. Raj, Kumaraswamy, G. N., and Ranganathaiah, C., “Interfacial stabilization of binary polymer blends through radiation treatment: A free volume approach”, in Physica status solidi. C, Conferences and critical reviews, 2009, vol. 6, pp. 2404-2406.[Abstract]


Blending is a widely used technique in polymer research to improve the physical/mechanical properties of homopolymers. Blending of two polymers may either result in a miscible system or immiscible system. From thermodynamic viewpoint whether one likes it or not, quite often immiscible or partially miscible blends are produced. In order for successful application of these types of blends, interfacial stabilization is required which are done through compatibilization. Recently compatibilization through radiation treatment in binary polymer blends have been gaining importance due to its advantages over other methods. Irradiation by high-energy radiation like electrons has been tried but with little success. The cross-linking between blend constituents which occurs after irradiation is expected to improve many properties such as optical, mechanical, electrical etc. On the other hand use of microwave-irradiation, which is an alternative to conventional heating, seems to be a promising approach for the above purpose. One expect that the polar group present in the blend systems may absorb the microwaves and thus become highly reactive thereby initiating improved interaction between the blend components thereby improving many properties. In the present study we have employed the positron lifetime method to study the microstructural changes brought out by e-beam and microwave irradiation in two polymer blend systems namely PS/PMMA and PVC/SAN through free volume monitoring. Though the free volume data shows the overall modification occurred in the blend sample, but it could not reveal the information about the actual site of modification whether it has occured at the interface or within the blend constituents. To overcome this hurdle, based on Wolf et al. theory we recently developed a new method [3] for characterizing the changes at the interface through hydrodynamic interaction existing between the constituents of binary polymer blend. The hydrodynamic interaction parameter α derived from the very same free volume data measures the excess friction generated at the interface between the chains of constituent polymers. It represents the strength of hydrodynamic interaction or it is a measure of the adhesion strength at the interface. Therefore, through the parameter α, the extent of interfacial stabilization occurred through irradiation in polymer blend systems can be effectively studied. In the present study, a comparison of results with e-beam and microwave induced phase modification is done to figure out which route is better to stabilize the interface depending upon the system of study. More »»

2007

Conference Paper

C. Ranganathaiah, Kumaraswamy, G. N., and Raj, J. M., “Measurement of hydrodynamic interaction parameter for miscibility test of polymer blends by positron lifetime method”, in Proceedings of DAE-BRNS symposium on nuclear and radiochemistry, 2007.[Abstract]


Positron Annihilation Lifetime Spectroscopy is used to determine the free volume content in the blends of SAN/PMMA and PS/PVC. Though the free volume data indicate the miscible/immiscible nature of the blends, the extent of miscibility for different weight compositions is not forthcoming. Therefore the hydrodynamic interaction parameter α which accounts for the excess friction between the constituents of the blend system is evaluated for this purpose. The SAN/PMMA system produces a maximum α of -209 at 20% of PMMA concentration while PS/PVC almost zero. It appears sound that hydrodynamic interaction parameter, α, is a suitable parameter to understand the composition dependent miscibility level in polymer blends. More »»

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