Thermal characteristics of the Langmuir-Blodgett film fabricated with bipyridinium bis-(tetracyanoquinodimethane anion radical) salts

Abstract

The phase transition of the headgroup in a Langmuir-Blodgett film fabricated with bipyridinum bis-(tetracyanoquinodimethane anion radical) salts attached with long chain alkyl groups has been studied using electron spin resonance spectroscopy. The Cia double chain attached more efficiently to the dipyridinium stabilized the alkyl chain and headgroup structure than the C(22) single chain. The stability of the film may be due to the size matching between headgroup and hydrocarbon. The headgroup melting temperature of the double chain compound was 367 K and that of the single chain compound was 347 K, which was identified by ESR spectroscopy. A pretransition between two gel states was found. The viscosity estimated with the rotational correlation time of electron spin resonance spectroscopy was 0.8 poise for the Langmuir-Blodgett films.