THE STRUCTURE OF LANGMUIR-BLODGETT-FILMS FROM SUBSTITUTED PHTHALOCYANINATO-POLYSILOXANES

Tetra(methoxy)tetra(octyloxy)phthalocyaninatopolysiloxane forms macroscopically oriented LB films with the long axes of the rigid-rod polymer molecules oriented parallel to the direction of film tranfer. The dichroic ratio of the absorption of the phthalocyanine chromophore which is 2.3 is used as the order parameter to quantity this orientation. The polarization of vibration modes with respect to the chain axis is evaluated from polarized transmission and "grazing-incidence reflection" (GIR) IR spectra. The analysis of the transmission spectra with respect to their linear dichroism gives a mean deviation of the polymer chain axis from the direction of film transfer in terms of a mean deviation angle of 〈sin2ψ〉, ψ = 35°. Quantitative analysis of the GIR spectra shows that the side-chain segments are randomly distributed around their polymer chain axes. Polarized resonance Raman spectra confirm the orientational order found by the other methods. Futhermore, the comparison with data on copper phthalocyanine allows more detailed analysis of the resonance Raman features. A two-dimensional order parameter is defined to quantify the in-plane orientation distribution of the polymer molecules. Its value can be derived from dichroism measurements. © 1990.