First Principles Study of Phase Transformations in Polyvinylidene Fluoride

Polyvinylidene fluoride (PVDF) with a small concentration of chlorotrifluoroethylene (CTFE) has been observed to store very high energy [1] as compared to currently used polymers. Chain rotations within the PVDF crystal have been proposed as the reason behind the high energy storage. However, in a recent work, we suggested [2] that the ultra-high energy storage in P(VDF-CTFE) is due to an electric-field induced phase transition from the non-polar $\alpha$ to the polar $\beta$-PVDF. We have now determined a low-energy relaxation path from $\alpha$- to $\beta$-PVDF which confirms this suggestion. Our first-principles calculations reveal an intricate relationship between the kinetics of the chain rotation and the phase transformatio \\[4pt] [1] B. Chun, Science \textbf{313}, 334 (2006).\\[0pt] [2] V. Ranjan, Phys. Rev. Lett. \textbf{99}, 047801 (2007).