Phase Inversion Processing of PVDF-HFP Membranes for Enhanced Ionic Liquid Uptake, β-Phase Content, and Electroactive Actuation
POSTER
Abstract
Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) is a widely used matrix for ionic-liquid-based electroactive polymer actuators, yet processing–structure–property relationships for high ionic liquid (IL) uptake and actuation remain poorly understood. We investigate how phase inversion processing of PVDF-HFP membranes can be used to simultaneously enhance IL uptake, stabilize the electroactive β-phase, and improve bending actuation.
PVDF-HFP membranes were prepared from a 15 wt% PVDF-HFP solution in a mixed N,N-dimethylformamide (DMF)/acetone solvent system (80/20 wt%), cast, and immersed in non-solvent baths under controlled phase inversion conditions. Dried membranes were subsequently equilibrated with the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI) under vacuum at elevated temperature, achieving IL uptake of ~400 wt%. The resulting morphology and crystalline phase content were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). Electroactive performance was assessed via bending actuation under an applied electric field of up to 20V.
We find that appropriately tuned phase inversion produces a porous yet mechanically robust morphology that significantly increases IL uptake relative to non–phase-inverted films, while also promoting a higher fraction of the β-phase. This work identifies simple phase inversion parameters as effective levers to tailor PVDF-HFP/IL actuator membranes and establishes a processing map linking casting conditions, β-phase formation, liquid uptake, and electro-mechanical response.
PVDF-HFP membranes were prepared from a 15 wt% PVDF-HFP solution in a mixed N,N-dimethylformamide (DMF)/acetone solvent system (80/20 wt%), cast, and immersed in non-solvent baths under controlled phase inversion conditions. Dried membranes were subsequently equilibrated with the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI) under vacuum at elevated temperature, achieving IL uptake of ~400 wt%. The resulting morphology and crystalline phase content were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). Electroactive performance was assessed via bending actuation under an applied electric field of up to 20V.
We find that appropriately tuned phase inversion produces a porous yet mechanically robust morphology that significantly increases IL uptake relative to non–phase-inverted films, while also promoting a higher fraction of the β-phase. This work identifies simple phase inversion parameters as effective levers to tailor PVDF-HFP/IL actuator membranes and establishes a processing map linking casting conditions, β-phase formation, liquid uptake, and electro-mechanical response.
*This material is based upon work supported by the National Science Foundation.
Presenters
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Nihad Ahmadli
- University of Houston