Study on the curie transition of P(VDF-TrFE) copolymer

International Conference on Chemistry and Material Science 2017

化学;材料科学

Septiyani Arifin, Devi Eka^1 ; Ruan, J.J.^2

Department of Metallurgical Engineering, Faculty of Engineering, Jenderal Achmad Yani University, Bandung, Indonesia^1

Department of Materials Science and Engineering, College of Engineering, National Cheng Kung University, Tainan, Taiwan^2

关键词: Confinement effects;    Curie transition;    Curie transition temperature;    Piezoelectric crystals;    Poly(vinylidene fluoride-trifluoroethylene);    Segmental rotations;    Solid-solid transitions;    Thermal kinetic energies;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/299/1/012056/pdf
DOI  :  10.1088/1757-899X/299/1/012056

学科分类：材料科学（综合）

来源: IOP

【 摘 要 】

A systematic study was carried out to decipher the mechanism of Curie transition of piezoelectric crystals of poly(vinylidene fluoride trifluoroethylene) P(VDF-TrFE). The unique polarity of P(VDF-TrFE) crystalline phase below curie transition temperature is attributed to the lattice packing of all-trans molecular chains, which allocates all the substituted fluorine atoms on one side of molecular chains and hydrogen atoms on the other side. Therefore, a net dipole moment is created across the lateral packing of molecular chains. Nevertheless, due to the mutual repulsion among fluorene atoms, this all-trans conformation is not stable, and ready to change above Curie temperature, where thermal kinetic energy is sufficient to cause segmental rotation. As being illustrated by in-situ recorded X-ray diffraction and thermal analysis, the concerned curie transition is deciphered as a one-step process which is involved two process and this is different from conventional one-step solid-solid transitions. Accompanied with this one-step process during heating, the occurrence of lamellar bending is inferred for elucidating the decline of stacking regularity of crystalline lamellae, which reversibly recover during subsequent cooling. However, as the crystalline lamellae of P(VDF-TrFE) are confined in between the stacking of crystalline lamellae of PVDF, lamellar bending is restricted accordingly. As a result, a certain fraction of the piezoelectric crystalline lamellae was found to survive through the Curie transition. Thus, in addition to the suggestion of a one-step process as a new concept for understanding the Curie transition, the relationship between the lamellar stacking and transition of molecular packing is unveiled as well in this research.