Non-equilibrium segmental dynamics driven by multiwall carbon nanotubes in PS/PVME blends

Xavier, Priti; Bose, Suryasarathi

doi:10.1039/c4cp00832d

Cited by 17 publications

(16 citation statements)

References 30 publications

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“…77 Bimodal relaxations suggesting different 'dynamical' environments were noted in the case of PS/PVME blends in the presence of MWNTs. 80 The dielectric loss modulus spectra showed a bimodal distribution in the presence of MWNTs. This is the characteristic of a heterogeneous environment.…”

Section: Polymer Grafted Nanoparticlesmentioning

confidence: 96%

Nanoparticle induced miscibility in LCST polymer blends: critically assessing the enthalpic and entropic effects

Xavier

Rao

Bose

2016

Phys. Chem. Chem. Phys.

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The use of copolymer and polymer blends widened the possibility of creating materials with multilayered architectures. Hierarchical polymer systems with a wide array of micro and nanostructures are generated by thermally induced phase separation (TIPS) in partially miscible polymer blends. Various parameters like the interaction between the polymers, concentration, solvent/non-solvent ratio, and quenching temperature have to be optimized to obtain these micro/nanophase structures. Alternatively, the addition of nanoparticles is another strategy to design materials with desired hetero-phase structures. The dynamics of the polymer nanocomposite depends on the statistical ordering of polymers around the nanoparticle, which is dependent on the shape of the nanoparticle. The entropic loss due to deformation of polymer chains, like the repulsive interactions due to coiling and the attractive interactions in the case of swelling has been highlighted in this perspective article. The dissipative particle dynamics has been discussed and is correlated with the molecular dynamics simulation in the case of polymer blends. The Cahn-Hillard-Cook model on variedly shaped immobile fillers has shown difference in the propagation of the composition wave. The nanoparticle shape has a contributing effect on the polymer particle interaction, which can change the miscibility window in the case of these phase separating polymer blends. Quantitative information on the effect of spherical particles on the demixing temperature is well established and further modified to explain the percolation of rod shaped particles in the polymer blends. These models correlate well with the experimental observations in context to the dynamics induced by the nanoparticle in the demixing behavior of the polymer blend. The miscibility of the LCST polymer blend depends on the enthalpic factors like the specific interaction between the components, and the solubility product and the entropic losses occurring due to the formation of any favorable interactions. Hence, it is essential to assess the entropic and enthalpic interactions induced by the nanoparticles independently. The addition of nanoparticles creates heterogeneity in the polymer phase it is localized. This can be observed as an alteration in the relaxation behavior of the polymer. This changes the demixing behavior and the interaction parameter between the polymers. The compositional changes induced due to the incorporation of nanoparticles are also attributed as a reason for the altered demixing temperature. The particle shape anisotropy causes a direction dependent depletion, which changes the phase behavior of the blend. The polymer-grafted nanoparticles with varying grafting density show tremendous variation in the miscibility of the blend. The stretching of the polymer chains grafted on the nanoparticles causes an entropy penalty in the polymer blend. A comparative study on the different shaped particles is not available up to date for understanding these aspects. Hence, we have juxtaposed the ...

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Section: Polymer Grafted Nanoparticlesmentioning

confidence: 96%

Nanoparticle induced miscibility in LCST polymer blends: critically assessing the enthalpic and entropic effects

Xavier

Rao

Bose

2016

Phys. Chem. Chem. Phys.

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“…It can be found that when the temperature is in the range where the segmental dynamics is active in the frequency window, the temperature‐dependent loss peaks corresponding to segmental dynamics ( α relaxation) of PVME can be superposed for unfilled, filled systems and the width and maximum of hardly change with the incorporation of A200 or R974, indicating that the nanoparticles can hardly retard the segmental dynamics of PVME in the homopolymer or miscible blend matrix. In some previous works, the restriction of segmental mobility is induced by surface adsorption of polymer to nanoparticles and then leads to the retarded kinetics of phase separation, while the influence of nanoparticles on the segmental dynamics is clearly not the main cause for the constrain phase separation in our study. Similar phenomenon with the unaltered glass transition temperature ( T g ) or segmental relaxation time ( τ seg ) were also observed for other nanocomposties …”

Section: Resultsmentioning

confidence: 46%

Evolution of concentration fluctuation during phase separation of polystyrene/poly(vinyl methyl ether) blend in the presence of nanosilica

Chen

Zuo

Yang

et al. 2017

J. Polym. Sci. Part B: Polym. Phys.

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The influence of nanosilica on the concentration fluctuation of polystyrene/poly (vinyl methyl ether) (PS/PVME) mixtures was investigated during phase separation. The amplitude of concentration fluctuation was quantified by dielectric spectrums based on the idea of Lodge-Mcleish model and the linearized Cahn-Hilliard theory could describe the amplitude evolution of concentration fluctuation at the early stage of phase separation. Hydrophilic nanosilica A200 dispersed in PVME-rich phase behaved an obvious inhibition effect on the concentration fluctuation of blend matrix, while hydrophobic nanosilica R974 dispersed in PS-rich phase had little effect on the concentration fluctuation. The kinetics and amplitude evolution of concentration fluctuation during phase separation for PS/PVME/A200 nanocomposites were remarkably restrained due to the surface adsorption of PVME on A200. As the segmental dynamics of PVME and PS in homogeneous matrix was hardly influenced by A200 and R974, the enhanced miscibility and the significantly constrained flow relaxation of PVME chains might contribute to the retarded concentration fluctuation of PS/PVME/A200 nanocomposites. While the weak interaction between R974 and components of blend matrix and little effect of R974 on the molecular dynamics of PS chains may result in the weak retardation of concentration fluctuation for blend matrix.

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“…13,29,30 In the case of PS/PVME blends, the segmental relaxations can be coupled with the conductivity. Apart from increasing the local concentration in a given phase, it also manipulates the phase separation dynamics.…”

Section: Evolution Of Electrical Conductivity Using Electro-rheology mentioning

confidence: 99%

Electromagnetic shielding materials and coatings derived from gelation of multiwall carbon nanotubes in an LCST mixture

Xavier

Bose

2014

RSC Adv.

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Thermally induced demixing in an LCST mixture, polystyrene (PS)/poly[vinyl methyl ether] (PVME), was used as a template to design materials with high electrical conductivity. This was facilitated by gelation of multiwall carbon nanotubes (MWNTs) in a given phase of the blends. The MWNTs were mixed in the miscible blends and the thermodynamic driven demixing further resulted in selective localization in the PVME phase of the blends. This was further confirmed by atomic force microscopy (AFM). The time dependent gelation of MWNTs at shallow quench depth, evaluated using isochronal temperature sweep by rheology, was studied by monitoring the melt electrical conductivity of the samples in situ by an LCR meter coupled to a rheometer. By varying the composition in the mixture, several intricate shapes like gaskets and also coatings capable of attenuating the EM radiation in the microwave frequency can be derived. For instance, the PVME rich mixtures can be molded in the form of a gasket, O-ring and other intricate shapes while the PS rich mixtures can be coated onto an insulating polymer to enhance the shielding effectiveness (SE) for EM radiation. The SE of the various materials was analyzed using a vector network analyzer in both the X-band (8.2 to 12 GHz) and the K u -band (12 to 18 GHz) frequency. The improved SE upon gelation of MWNTs in the demixed blends is well evident by comparing the SE before and after demixing. A reflection loss of À35 dB was observed in the blends with 2 wt% MWNTs. Further, by coating a layer of ca. 0.15 mm of PS/PVME/MWNT, a SE of À15 dB at 18 GHz could be obtained.

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Non-equilibrium segmental dynamics driven by multiwall carbon nanotubes in PS/PVME blends

Cited by 17 publications

References 30 publications

Nanoparticle induced miscibility in LCST polymer blends: critically assessing the enthalpic and entropic effects

Nanoparticle induced miscibility in LCST polymer blends: critically assessing the enthalpic and entropic effects

Evolution of concentration fluctuation during phase separation of polystyrene/poly(vinyl methyl ether) blend in the presence of nanosilica

Electromagnetic shielding materials and coatings derived from gelation of multiwall carbon nanotubes in an LCST mixture

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