Studies on the Langmuir–Blodgett films of polythiophene containing a mesogenic side chain

Abstract

Polythiophene containing hexyloxy (PTC6) and tetradecyloxy (PTC14) mesogenic side chains were synthesized. Langmuir films of these polymers at the air/water interface were characterized using surface pressure–area (π–A) isotherms and hysteresis from compression – expansion cycle using two spreading solvents, CHCl₃ and CH₂Cl₂. Langmuir–Blodgett films (LB films) of these polymers were transferred to quartz, silicon and ITO substrates and were analyzed using polarized UV-Vis, and Fluorescence. The orientation of the different functional groups in the LB films was compared with spin coated films using polarized FTIR. The studies show that LB films of PTC6 in CH₂Cl₂ show a high dichroic ratio suggesting high orientation. Atomic force microscopy (AFM) study reveals the high particulate size morphology in LB films of PTC6. The results from the studies show that solvation and the length of the non-chromophoric alkoxy side chain control the formation of thin films, order and the optical properties of the films.