Laser Raman Optical-Wave-Guide Study of Mono- and Multilayer Langmuir-Blodgett Films of Poly(diacetylenes) Containing a Carboxylic Acid Group

Coherent mono- and multilayer polymer films of the 11–8 diacetylenic fatty acid CH₃-(CH₂)11C≡CC≡C(CH₂)₈COOH were formed by the Langmuir-Blodgett technique. The films thus formed were characterized by traditional force-area isotherms while on a pure water subphase. Molecular organization in both mono- and multilayer films was investigated by the resonance Raman optical-wave-guide method. Our results show that the molecular organizations in both the monolayer and multilayer films are the same and also show no dependence on the nature of the substrate. Furthermore, both monolayer and multilayer films can be prepared in either blue or red forms. The study of the Raman spectral change as a function of the blue-to-red polymer-form conversion reveals that the phase transformation involves a two-phase heterogeneous process.