原位高压下聚偏二氟乙烯(PVDF)的结构相变OA

Polyvinylidene fluoride(PVDF)is a versatile semi-crystalline polymer exhibiting outstanding piezoelectric,pyroelectric and dielectric properties,and is therefore widely employed in sensors,energy devices and biomedical applications.Its performance is governed by crystallinity and the polymorphic constitutiona(α,β,γ,δ,ε),among which the polar β-phase possesses superior electromechanical characteristics compared with the non-polar α-phase.Nevertheless,the α-phase remains the most stable and the most readily obtained thermodynamical form.The structural evolution of PVDF under high pressure is investigated by means of in situ X-ray diffraction and Fourier-transform infrared spectroscopy.At ambient conditions the powder consists primarily of the α-phase with a minor fraction of β.Upon compression to 0-20 GPa,the α phase gradually diminishes;the emergence of new diffraction peaks and band shifts indicates sequential α→β and β→γ transformations,accompanied by a pronounced increase in β content and concomitant formation of γ.When the pressure exceeds 20 GPa,severe lattice distortion destroys long-range crystalline order,resulting in peak broadening and eventual amorphization.The study unveils the intricate interplay between pressure-induced chain rearrangement and polymorphic transitions,clarifies the high-pressure phase-transformation pathway and structural evolution of PVDF,and thereby deepens the structure-property understanding of this polymer.The findings also provide a theoretical basis for tailoring its performance under extreme conditions and for designing high-pressure technologies.