Ultrathin Films from Fluorine Containing Polymers: Fabrication and Characterization

Abstract

Monolayers and ultrathin films of some fluorine containing polymers were prepared by the Langmuir-Blodgett (LB) technique. The polymers were obtained using two main synthetic approaches: firstly, polyamide (PA-1) and polyimide (PI-1) were prepared from direct polycondensation of 4,4′-hexafluoroisopropylidenediphthalic anhydride and 4,4′-hexafluoroisopropylidenedianiline in N-methyl-2-pyrrolidone (NMP). The thermogravimetric analysis (TGA) for PI-1 yielded 580°C by 1% weight loss. They formed stable monolayers with a collapse pressure of 62 mN/m and a collapse area of 0.20 nm2 per repeat unit (R.U.) in the case of PA-1, for PI-1 the collapse pressure was 60 mN/m associated with a collapse area of 0.23 nm2 per R.U. Secondly, poly[(maleic acid perfluorooctylamide-imide)-co-ethylene] (PAPE) with fluorinated side chains was synthesized from poly[(maleic anhydride)-co-ethylene]. They formed stable monolayers too. Multilayer depositions onto various substrates were possible for all the synthesized polymers. LB films were characterized by ultra-violet/visible spectroscopy (UV-Vis), surface plasmon resonance (SPR), dielectric spectroscopy and atomic force microscopy (AFM). Gas phase polymerization of tetrafluoropropyl methacrylate (TFPM) was carried out in the presence of macroinitiator, poly[octadecene-co-(maleic anhydride)] modified with tert-butyl hydroperoxide. Film thickness could be controlled on different hydrophobic substrates varying the reaction time.