Giant Electrostriction via Nanodomain Engineering in Relaxor Ferroelectric Polymers

Area of Science:

• Materials Science
• Polymer Science
• Nanotechnology

Background:

• Relaxor ferroelectric (RFE) polymers are promising for artificial muscles due to high strain, stress, and response speed.
• The structural basis for their large electrostrictive deformation is not fully understood.

Purpose of the Study:

• Investigate the structural origin of differing electrostrictive properties in P(VDF-TrFE)-based RFE terpolymers.
• Understand the role of termonomers (CFE vs. CTFE) and semicrystalline structure on electrostriction.

Main Methods:

• Synthesis of P(VDF-TrFE)-co-CFE (terP-CFE) and P(VDF-TrFE)-co-CTFE (terP-CTFE) terpolymers.
• In situ electric poling combined with time-resolved wide-angle X-ray diffraction (TR-WAXD), small-angle X-ray scattering (SAXS), and Fourier transform infrared (FTIR) spectroscopy.
• Analysis of semicrystalline morphology and crystal phase transitions.

Main Results:

• TerP-CFE achieved a record transverse strain of ~10.6%, while terP-CTFE showed only ~4.2% at 190 MV/m.
• An RFE-to-ferroelectric (FE) crystal phase transition was observed in terP-CFE but not in terP-CTFE.
• Oriented amorphous fraction and crystalline defects (taut-tie molecules) were found to significantly enhance electrostriction.

Conclusions:

• The observed difference in electrostriction is attributed to the RFE-to-FE crystal phase transition in terP-CFE.
• Defect engineering within the semicrystalline structure is crucial for optimizing electrostrictive properties in RFE polymers.
• This research provides a foundation for designing advanced artificial muscle materials.