Facile preparation of highly oriented poly(vinylidene fluoride) Langmuir-Blodgett nanofilms assisted by amphiphilic polymer nanosheets

We describe a facile and novel method for preparing highly dense Langmuir-Blodgett (LB) nanofilms of poly(vinylidene fluoride) (PVDF) with precisely adjustable film thickness from several to hundreds of nanometers, assisted by amphiphilic poly(N-dodecylacrylamide) (pDDA) nanosheets. Even at a molar mixing ratio of PVDF:pDDA up to 50:1, the high collapse surface pressure of 44.4 mN/m obtained using this method is a breakthrough for the preparation of PVDF LB nanofilms, which is devoted to the resulting high-density PVDF nanofilms. As shown by FTIR and XRD measurements, the mixed LB nanofilms without any postprocessing comprised dominant ferroelectric β phase of ∼95% and negligible paraelectric α phase. Furthermore, through control of the surface pressure, controllable PVDF crystal morphologies were achieved. Moreover, β phase PVDF dominates in all cases. After applying a dc bias of 5 V through a conductive cantilever, the local polarized pattern on the surface of a nine-layer mixed LB nanofilm observed using Kelvin probe force microscopy indicates that it is possible to induce all dipoles in one direction in the mixed LB nanofilm, which is promising for application in low-voltage nanoelectronics.