Effect of Trough Parameters and Substrates on the PVDF LB Films

Abstract

Polyvinylidene Fluoride (PVDF) is known to have some very attractive mechanical, electrical and chemical properties. It is being used for parts and applications that require high purity and great mechanical strength. PVDF exists in several crystallized phases such as a nonpolar α-phase, a polar β-phase, a partially polar γ-phase, a partially polar δ-phase, and a nonpolar ε-phase. For various applications, polar β crystals are of critical importance because they show ferroelectric properties. The Langmuir-Blodgett (LB) technique is an effective method for producing thin films of PVDF homopolymer with ferroelectric β phase. In this work, the effect of varying the trough parameters on PVDF homopolymer Langmuir films was studied. These films were fabricated on different types of substrates by the LB deposition method. The changing of compression rate and subphase temperature was reflected on the monolayers as they were characterized using the surface pressure-area isotherms. Initially, the most suitable conditions for the final deposition were the one having a maximum value of static elasticity of solid phase at any specified parameter. The stability of a monolayer at a particular compression rate was confirmed by the cyclic expansion and compression. The oscillating barrier experiment was performed at various values of compression rate and the subphase temperature. This was done to calculate the value of dynamic elasticity of the monolayer and to verify the conditions decided for the final deposition. Finally, the deposition of monolayers was done only for the upstrokes one at a time. For the purpose of depositing multiple layers the process of changing the subphase and dispersing the monolayer was done after the deposition of every layer.