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Polymer nanocomposites exhibit unique effective properties that do not follow conventional effective media approaches. The nanoparticle-polymer interphase has been shown to strongly influence the nanocomposites behavior due o its significant volume when the particles are nano-sized, affording an opportunity to tune the dielectric response of the resulting nanocomposite. In this study, we investigate the effects of TiO2 nanoparticles on the electrical properties and the charges distribution and transport in polydimethylsiloxane (PDMS) nanocomposites. Impedance spectroscopy shows suppression of interfacial Maxwell-Wagner-Sillars (MWS) polarization accompanied by a reduction in the low frequency dielectric permittivity and loss at high temperatures in the presence of the TiO2 nanoparticles. Thermally stimulated discharge current measurements confirm that the suppression of the interfacial polarization relaxations happens by redistributing or depleting the charges through the composite and hindering their mobility, potentially resulting in lower electrical conduction and higher breakdown strength. Although the model materials investigated here are TiO2 nanoparticles and Sylgard 184 PDMS, our findings can be extended to other nanoparticulate-filled elastomer composites to design lightweight dielectrics, actuators and sensors with improved capabilities.
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Poisson ratio mismatch drives low-strain reinforcement in elastomeric nanocomposites
Introduction of nanoparticulate additives can dramatically impact elastomer mechanical response, with large enhancements in modulus, toughness, and strength. Despite the societal importance of these effects, their mechanistic origin remains unsettled. Here, using a combination of theory and molecular dynamics simulation, we show that low-strain extensional reinforcement of elastomers is driven by a nanoparticulate-jamming-induced suppression in the composite Poisson ratio. This suppression forces an increase in rubber volume with extensional deformation, effectively converting a portion of the rubber's bulk modulus into an extensional modulus. A theory describing this effect is shown to interrelate the Poisson ratio and modulus across a matrix of simulated elastomeric nanocomposites of varying loading and nanoparticle structure. This model provides a design rule for structured nanoparticulates that maximizes elastomer mechanical response via suppression of the composite Poisson ratio. It also positions elastomeric nanocomposites as having a qualitatively different character than Poisson-ratio-matched plastic nanocomposites, where this mechanism is absent.
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- Award ID(s):
- 1650460
- PAR ID:
- 10127595
- Date Published:
- Journal Name:
- Soft Matter
- Volume:
- 15
- Issue:
- 4
- ISSN:
- 1744-683X
- Page Range / eLocation ID:
- 656 to 670
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/c8sm02333f
