Poly(vinylidene fluoride) under finite electric displacement fields: a removable α → δ reorientation barrier and a persistent first-order δ → β conformational change

Research by Shaohui Qiu¹, Jacob C. Dean¹, Rajagopalan Thiruvengadathan², Ramanujam Brahmadesam Thoopul Srinivasa Raghava^3,4, and Yiming Su^5,6

¹Department of Chemistry and Physics, Southern Utah University, Cedar City, Utah, USA; ²Department of Engineering and Technology, Southern Utah University, Cedar City, Utah, USA; ³Department of Physics, Amrita School of Physical Sciences, Amrita Vishwa Vidyapeetham, Coimbatore, India; ⁴Functional Materials Laboratory, Amrita School of Engineering, Amrita Vishwa Vidyapeetham, Coimbatore, India; ⁵Utah Water Research Laboratory, Logan, Utah, USA; ⁶Department of Biological and Chemical Engineering, Utah State University, Logan, Utah, USA

Polyvinylidene fluoride (PVDF) is a polymer whose electrical properties depend on how its molecular chains are arranged. The material can take several structural forms, including three known as alpha (α), delta (δ), and beta (β). The forms have differing molecular arrangements and responses to electrical forces. Researchers can transform PVDF from one form to another by applying an electric field or mechanically stretching the material, but they have not fully understood why these methods produce different results.

Using quantum-mechanical computer simulations on computational resources at the Center for High Performance Computing, Qiu et al. investigated how electrical conditions affect the stability of these three forms and how much energy each transformation requires. Their calculations show that changing the electrical conditions can favor a progression from the α form to the δ form and eventually to the β form. The transition from α to δ requires relatively small changes in molecular structure and becomes much easier under stronger electrical conditions. In contrast, the transition to β requires substantial straightening and stretching of the polymer chains. This transformation remains energetically difficult, even under strong electrical conditions. The researchers also identified conditions under which the δ and β forms can coexist.

Molecular structures of three forms of polyvinylidene fluoride (PVDF): alpha, delta, and beta. The alpha form has opposing electrical polarizations in neighboring chains, while the delta and beta forms have aligned polarizations. The beta form also features straighter molecular chains. — Molecular structures of three forms of polyvinylidene fluoride (PVDF): α (left), δ (center), and β (right). The α and δ forms have similar molecular structures but differ in the alignment of their electrical polarizations. The β form features straighter molecular chains, helping explain why researchers typically use mechanical stretching rather than an electric field alone to produce it. Credit: Qiu *et al.*, preprint on arXiv (2610.31926, 2026).

These findings help explain why applying an electric field tends to produce the δ form, while producing the β form generally requires mechanical stretching. The results also suggest that modifying how the polymer's molecular structure responds to electrical forces could make it possible to produce the β form using an electric field alone. Although the team primarily modeled idealized conditions at absolute zero, their preliminary estimates indicate that temperature may affect the relative stability of the different structures. The study provides a foundation for developing new ways to control the molecular structure and electrical properties of PVDF.

The researchers shared a preprint of their manuscript if you would like to learn more.