Spectroscopic characteristics of 9-cyanoanthracene mixed with polymethyl methacrylate and stearic acid in Langmuir–Blodgett films

Multilayers of 9-cyanoanthracene (CNA) mixed with stearic acid (SA) as well as also polymethyl methacrylate (PMMA) at different mole fractions of CNA have been transferred onto quartz substrate to form stable Langmuir–Blodgett (LB) films. Surface pressure versus area per molecule isotherms confirms the formation of stable films. The absorption and fluorescence spectra of CNA–SA and CNA–PMMA mixed LB films were compared. In case of CNA–SA mixed LB films, even at very low mole fraction of CNA, aggregation was formed. While in case of CNA–PMMA mixed LB films, at very low mole fraction of CNA, no aggregation was formed. However with increasing mole fraction of CNA in PMMA formation of aggregate started which is indicated by the development of a new band in the absorption spectra. At higher concentration this band overlaps with the high energy band to form a broad band profile in the absorption spectra. Steady-state fluorescence spectra also confirm these phenomena.