Study on the growth of functional crystals guided by coalescence and stacking behaviors of P(VDF-TrFE) ferroelectric lamellar crystals

Abstract

The unique polarity of P(VDF-TrFE) crystalline phase below curie transition temperature is attributed to the lattice packing of all-trans molecular segments which allocates most of substituted fluorine atoms on one side of molecular segments and hydrogen atoms on the other side In this study the growth habits and stacking behavior of crystalline lamellae within thin films were explored The coalescence of lamellar crystals has been identified to occur during the secondary crystallization above Curie temperature It is viewed that for the residue amorphous fractions in between lamellar crystals the further crystallization above Curie temperature causes the assembly and coalescence of present lamellar crystal With the presence of a limited fraction of amorphous poly(methyl methacrylate) (PMMA) the continuous coalescence and growth of lamellar crystals eventually result in regular stacking arrays Furthermore the shrinkage and deformation of the PMMA domains is observed as a result of continuous lamellae growth above the Curie temperature and then the PMMA domains extends along the stacking direction of lamellar crystals The fullerene derivative of [6 6]-phenyl C61 butyric acid methyl ester (PCBM) is observed to preferentially assemble into PMMA globular domains during solution casting Due to the stress from deformed amorphous environment the later induced crystal growth of PCBM is identified to be generally along the PMMA extension direction The anisotropic deformation of PMMA amorphous domains is thus realized able to modify crystal growth within deformed domains The involved phase interactions is expected to yield fruitful influences on the evolution of thin-film structures for desired physical properties

Date of Award	2019
Original language	English
Supervisor	Jr-Jeng Ruan (Supervisor)