Effects of polymer polarity on the interface interaction of polymer/liquid metal composites

Soft polymer/liquid metal (LM) composites have attracted considerable interest in flexible electronic energy fields. Interface interaction is a key issue that limits the improvement of their electrical performances and energy density. This paper investigates the influence of the polymer polarity on the interface interaction of composites. Four polymer matrixes-polypropylene (PP), polyethylene terephthalate (PET), polyvinylidene fluoride (PVDF), and poly(vinylidenefluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) were used. It was found that the order of interaction obeyed the order of the polymer polarity: PP/LM < PET/LM < PVDF/LM ≤ (P(VDF-TrFE-CFE))/LM. The increase in polymer polarity significantly promotes the dipole-dipole interaction between polar groups of polymers and the oxide shell of the LM. The best high-polarity PVDF/LM composites display good interface interaction to suppress the dielectric loss, facilitating the PVDF/LM films to exhibit increased capacitive storage density (+44%, 1.68 J cm^-3) without degrading the energy efficiency (80%). Our findings will guide researchers to design and choose matrix materials for achieving more improved performance of LM devices.