Molecular Modulation of Structure and Ferroelectric Performance of Poly( vinylidene fluoride) Free Standing Films from Aspects of Molecular Weight and Crystallization Temperature

作者：MENG Nan; LIAO Yaozu

来源：Journal of Donghua University(English Edition), 2022, 39(1): 1-6.

DOI：10.19884/j.1672-5220.202104018

• ferroelectric polymer
• poly ( vinylidene fluoride ) ( PVDF )
• solution casting
• remnant polarization
• dielectric constant

Ferroelectric polymer poly ( vinylidene fluoride ) ( PVDF) has received great research interest because of its special electroactive properties which are strongly dependent on the crystalline structures and in turn processing conditions. The effect of molecular weight and crystallization temperature on the micro-structure and macro-properties of PVDF films casted from dimethyl sulfoxide ( DMSO ) solvent is investigated. The results demonstrated that a low molecular weight ( 180 kg/mol ) and a low evaporation temperature ( 50 ℃) favored the formation of polar γ-phase, while a high molecular weight ( 1000 kg/mol ) and a high evaporation temperature ( 125 ℃) made PVDF crystallize into α-phase. Compared with films casted at 50 ℃, films casted at 125 ℃ exhibited higher dielectric loss at a low electric field and less loss conductivity at a high electric field, which was due to their low degrees of crystallinity and fine evaporation of the solvent, respectively. PVDF with a molecular weight of 180 kg/mol casted at 125 ℃ exhibited the highest remnant polarization ( 0. 062 C/m2 ) among all of the solution-processed films, being a result of high chain mobility resulted from the low molecular weight.