Langmuir and Langmuir-Blodgett (LB) films of 4-dicyanomethylene,4H-cyclopenta[2,1-b,3,4-b′] dithiophene

Attempts at forming Langmuir monolayers and Langmuir-Blodgett (LB) multilayer films of 4-dicyanomethylene-4H-cyclopenta[2,1-b,3,4-b']dithiophene (CDM), a low bandgap polymer precursor, are reported for the first time. The CDM was rendered soluble in different mixtures of common organic solvents with acetonitrile (CH3CN). Highly condensed monolayers of both the CDM monomer and mixed films with stearic acid were obtained on ultrapure water, and transferred by vertical dipping onto glass, ITO (indium tin oxide-coated glass) and gold surfaces with good visual uniformity. The LB films were characterized by UV-vis and Raman spectroscopy, atomic force microscopy (AFM), and DC electrical conductivity (sigma) measurements. AFM images show that deposited films are composed of microscopic crystallites, indicating that microcrystallites of CDM are formed during spreading and/or compression on the subphase surface. Comparing the average him thickness with the unit cell dimensions deduced from X-ray diffraction supports this view. The in-plane conductivity of pure CDM LB him was found to be similar to 2 X 10(-9) S/cm. (C) 2000 Elsevier Science S.A. All rights reserved.