| 초록 |
We developed freeze drying as a versatile processing technique for polymeric nanostructures. Monodisperse poly(vinylidene fluoride) (PVDF) nanostructures, whose aspect ratio and molecular alignment could be controlled, were fabricated by confined directional freezing process in anodic aluminum oxide membranes. Two major parameters, solution concentration and 3D temperature distribution, were controlled to reliably control the nucleation and crystal growth of PVDF. Regarding the first parameter, an increase in concentration increased aspect ratio from nanospheres to nanorods. Single crystalline nanospheres could be obtained at a low concentration cases. A plausible mechanism involves uniform nucleation in confined space and subsequent diffusion-controlled or confined directional growth. Under unidirectional temperature gradient, PVDF crystallized into an anisometrically oriented ferroelectric g form of nanospheres, nanocapsules and nanorods in confined spaces. |
