To modulate thermal conductivity of poly(vinylidene fluoride) by electric fields.

Phonon engineering focusing on the heat transport modulation on the atomic scale has arisen in recent decades. In addition to the reported ways of phonon engineering like controlling material size, doping and mechanical stretching, in this work, we show that electric field can also modulate heat transport. Thermal conductivity of poly(vinylidene fluoride) (PVDF), one typical electroactive ferroelectric polymer, is investigated by molecular dynamics simulation. Interestingly, the electric-field-poled PVDF array shows higher thermal conductivity than that of unpoled one along all three directions, and the enhancement ratio approach 225% along the polarization direction. The morphology and phonon property analysis reveal that the enhancement of thermal conductivity arises from the higher inter-chain lattice order, stronger inter-chain interaction, higher phonon group velocity and suppressed phonon scattering in poled PVDF. Moreover, it shows that the enhancement is more obvious at lower temperature. Investigation on thermal conductivity versus electric field shows that the enhancement is transient after the field exceeds the threshold. Our study offers a new strategy of phonon engineering.