(6et) Unique Physicochemical Phenomena in Polymer Nanocomposites

Unique physicochemical phenomena in polymer nanocomposites (PNCs), including giant magnetoresistance (GMR), negative permittivity, interfacial polarization and reduced viscosity attracted more attention owing to their significant effects on both the scientific community and the practical applications. However, how to achieve the properties by tailoring the structure of the PNCs is still unknown. Understanding the structure-property relationship is the key solution to the challenge, which strongly relies on mechanism study of these phenomena. Semi-conductive nanocomposites with the aforementioned unique properties have been developed and are applied to explore the working mechanism. In composition optimization and structure design, materials with different magnetic property, electrical conductivity and morphologies will be integrated to achieve the targeting performances and reveal the structure-property-performance relationship.

Targeting the GMR and negative permittivity, a surface initiated polymerization method has been developed to fabricate the polyaniline (PANI) nanocomposites with ferrite and perovskites nanoparticles, the polymerization process takes place on the surface of the nanoparticles and the microstructure study reveals a distinctive structure with the insulated nanoparticles coated by the conductive PANI. Depending on the localization or delocalization function of the nanoparticle plays on PANI, PNCs show different GMR value. PNCs with ferrite nanoparticles show negative GMR and positive real permittivity, however, the PNCs with perovslites nanoparticles have positive GMR and negative real permittivity. The positive and negative GMR were analyzed theoretically from the wave functional shrinkage model and forward interference model, respectively. And the negative permittivity was attributed to the delocalization of charges and the metallic state in PANI.

Targeting the reduced viscosity and interfacial polarization, PNCs with different kinds of conductive nanofillers including polyaniline nanofibers and nanospheres, polypyrrole nanofibers and nanospheres, carbon coated iron (Fe@C) nanospheres, carbon nanotubes, graphene nanosheets and graphene nanosheets decorated with core-shell nanoparticles have been fabricated. The embedded nanoparticles in polymer matrix were found to favor the disentanglement of the polymer chain. And the reduced viscosity of PNCs was attributed to the attraction between the nanofiller and polymer matrix caused by physical or chemical mechanism. The interfacial polarization were found to depending on the specific surface area of the nanofiller, an enlarged interfacial area between the nanofiller and polymer matrix allows more charge carriers blocked at the interfaces and leads to enhanced interfacial polarization.  

SELECTED PEER-REVIEWED PUBLICATIONS (7 out of 28):

1. X. Zhang, V. Bitaraf, H. A. Colorado, S. Wei and Z. Guo, Vinyl Ester Resin: Rheological Behaviors, Curing Kinetics, Thermo-mechanical and Tensile Properties, AIChE Journal, 60(1), 266-274 (2014).
2. X. Zhang, O. Alloul, Q. He, J. Zhu, M. J. Verde,Y. Li, S. Wei and Z. Guo, Strengthened Magnetic Epoxy Nanocomposites with Protruding Nanoparticles on the Graphene NanoSheets, Polymer, 54(14), 3594–3604 (2013).
3. X. Zhang, O. Alloul, J. Zhu, Q. He, Z. Luo, H. A. Colorado, N. Haldolaarachchige, D. P. Young, T. D. Shen, S. Wei and Z. Guo, Iron Core Carbon Shell Nanoparticles Reinforced Electrically Conductive Magnetic Epoxy Resin Nanocomposites with Reduced Flammability, RSC Advacnes, 3, 9453-9464 (2013).
4. X. Zhang, Q. He, H. Gu, S. Wei and Z. Guo, Polyaniline Stabilized Barium Titanate Nanoparticles Reinforced Epoxy Nanocomposites with High Dielectric Permittivity and Reduced Flammability, Journal of Materials Chemistry C, 1, 2886-2899 (2013). 
5. X. Zhang, Q. He, H. Gu, H. A. Colorado, S. Wei and Z. Guo, Flame Retardant   Electrical Conductive Nano-polymers based on Bisphenol F Epoxy Resin Reinforced with Nano Polyanilines, ACS Applied Materials & Interfaces, 5(3) 898-910 (2013).
6. X. Zhang, S. Wei, N. Haldolaarachchige, H. A. Colorado, Z. Luo, D. P. Young and Z. Guo, Magnetoresistive Conductive Polyaniline - Barium Titanate Nanocomposites with Negative Permittivity, Journal of Physical Chemistry C, 116(29), 15731–15740 (2012).
7. X. Zhang, J. Zhu, N. Haldolaarachchige, J. Ryu, D. P. Young, S. Wei, and Z. Guo, Synthetic Process Engineered Polyaniline Nanostructures with Tunable Morphology and Physical Properties, Polymer, 53(10), 2109–2120 (2012).

AWARDS/HONORS:

1. 3^nd Place Research Excellence Award in the 2013 Chinese-American Chemical Society Southwest Chapter (CACS-SW) Annual Poster Competition, Houston, TX, USA, October 2013.
2. Honorable Mention Award in student poster competition at International Polyolefins Conference 2013, Houston, TX, USA, February 2013.
3. Scholarship Award, SPE (Society of Plastics Engineers) Thermoplastic Materials & Foams Division, at International Polyolefins Conference 2013, Houston, TX, USA, February 2013.
4. 2^nd Place Research Excellence Award in the 2011 Chinese-American Chemical Society Southwest Chapter (CACS-SW) Annual Poster Competition, Houston, TX, USA, October 2011.