Fabrication of FerroelectricPolymer Nanocrystals with Tunable Morphologies.

We developed a procedure for the reliable and reproducibleformation of monodispersed polymer nanocrystals whose morphologiescan be easily controlled to produce structures ranging from nanoparticlesto nanorods. The directional cooling crystallization of ferroelectricpolymer solutions under nanoconfinement allowed polyvinylidene fluorideto form single crystalline monodisperse nanocrystals without the useof surfactants or stabilizers. An important growth condition necessaryto yield highly crystalline ferroelectric polymers was a regulatedthermal gradient under nanoconfinement to induce uniform nucleationand controlled directional growth. While other methods involving thenanoconfined crystallization of polymers are restricted to yield nanofibersor nanotubes with a high aspect ratio, our unidirectional coolingmethod produced nanocrystals of ferroelectric polymers with nanosphere,nanocapsule, and nanorod structures. Field-emission scanning electronmicroscopy, transmission electron microscopy, dynamic contact electrostaticforce microscopy, grazing incidence X-ray diffraction, and differentialscanning calorimetry were used to characterize the morphologies andstructures of the nanocrystals. The results suggest that the directionalcooling method facilitates nucleation and directional growth by controllingdiffusion and promoting molecular alignment from the preferred crystalorientations due to the unidirectional thermal gradient. This studyprovides a novel method of rational material design to fabricate polymernanocrystals by directing nucleation and growth of molecular crystalsfrom solution. [ABSTRACT FROM AUTHOR]