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 (Ba0.9 K0.1 TiO2.9F0.1, 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.

中文翻译：

---

PNIPAm水凝胶-KF掺杂钛酸钡纳米粒子复合材料中的Maxwell-Wagner-Sillars动力学和增强的射频弹性力学敏感性。

在由高k纳米粒子悬浮的水凝胶组成的杂化聚合物复合材料中，研究了麦克斯韦-瓦格纳-西拉（MWS）动力学和体积相变的电磁射频（RF）驱动。使用聚乙烯醇（PVA）将聚（N-异丙基丙烯酰胺）（PNIPAm）水凝胶与10％掺杂KF的钛酸钡（Ba0.9 K0.1 TiO2.9F0.1，KBT）纳米粒子混合，该纳米粒子具有高度各向异性的介电性能形成纳米颗粒-水凝胶复合物。尽管在合成过程中添加PVA可以保持很强的体积相变，并且具有类似于标准本体PNIPAm的极化和弛豫特性，但是KBT纳米颗粒的加入由于分子内相互作用的电荷筛选而导致体积相变和MWS极化降低。添加的纳米粒子和改进的合成工艺提高了整体PNIPAm的介电常数，将RF电导率提高了7倍，并且降低了比热，同时仍保持了不连续的体积相变。发射频率为544 kHz的RF天线仅能在合成后的复合材料与大体积PNIPAm之间实现复合材料的相变。测得的加热速率比未修饰的PNIPAm高3倍。