Maxwell-Wagner-Sillars Dynamics and Enhanced Radio-Frequency Elastomechanical Susceptibility in PNIPAm Hydrogel-KF-doped Barium Titanate Nanoparticle Composites

Ezekiel Walker; Yukikuni Akishige; Tong Cai; James Roberts; Nigel Shepherd; Shijie Wu; Zhiming Wang; Arup Neogi

doi:10.1186/s11671-019-3171-z

Maxwell-Wagner-Sillars Dynamics and Enhanced Radio-Frequency Elastomechanical Susceptibility in PNIPAm Hydrogel-KF-doped Barium Titanate Nanoparticle Composites

Nanoscale Res Lett. 2019 Dec 19;14(1):385. doi: 10.1186/s11671-019-3171-z.

Authors

Ezekiel Walker^{1

2}, Yukikuni Akishige³, Tong Cai⁴, James Roberts⁴, Nigel Shepherd⁵, Shijie Wu⁶, Zhiming Wang⁶, Arup Neogi⁴

Affiliations

¹ Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, 610054, People's Republic of China. ezekiel.walker@echonovus.com.
² Department of Physics, University of North Texas, 210 Avenue A, Denton, USA. ezekiel.walker@echonovus.com.
³ Faculty of Education, Shimane University, Matsue, Shimane, Japan.
⁴ Department of Physics, University of North Texas, 210 Avenue A, Denton, USA.
⁵ Department of Materials Science and Engineering, University of North Texas, Discovery Park E118, Denton, USA.
⁶ Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, 610054, People's Republic of China.

Abstract

Maxwell-Wagner-Sillars (MWS) dynamics and electromagnetic radio-frequency (RF) actuation of the volumetric phase change are investigated in a hybrid polymer composite consisting of hydrogel suspended with high-k nanoparticles. Poly(N-isopropylacrylamide) (PNIPAm) hydrogels were combined with 10% KF-doped barium titanate (Ba_0.9 K_0.1 TiO_2.9F_0.1, KBT) nanoparticles with highly anisotropic dielectric properties using poly(vinyl alcohol) (PVA) to form a nanoparticle-hydrogel composite. Whereas the addition of PVA to the synthesis maintains a strong volumetric phase transition with polarization and relaxation features similar to standard bulk PNIPAm, the addition of KBT nanoparticles results in reduced volumetric phase transition and MWS polarization due to charge screening of intramolecular interactions. The added nanoparticles and modified synthesis process enhanced the dielectric permittivity of bulk PNIPAm, increased RF conductivity up to 7×, and decreased the specific heat while still maintaining a discontinuous volumetric phase transition. An RF antenna emitting at 544 kHz was only able to actuate a phase change in the composites with modified synthesis versus bulk PNIPAm. Measured heating rates were 3× greater than that of un-modified PNIPAm.

Keywords: Dielectric; High-k nanoparticles; Hydrogel; Maxwell-Wagner-Sillars; PNIPAm; Permittivity; Radio frequency.

Grants and funding

N/A/Japan Society for Physics Students