Monolayer Behavior and LB Film Structure of Poly(2-methoxy-5-(n-hexadecyloxy)-p-phenylene vinylene)

Abstract

A PPV derivative, poly(2-methoxy, 5-(n-hexadecyloxy)-p-phenylenevinylene) (MH−PPV), has been synthesized by the Gilch route to study the influence of long alkyl side chains on the organization behavior of film at the air−water interface and multilayer structure obtained by Langmuir−Blodgett technique. The π−A isotherm, hysteresis, and film stability are used to characterize the behavior of a monolayer film at the air−water interface. Small-angle X-ray diffraction (SAXRD), UV−visible spectra, and FTIR are applied to study the conformation and orientation of the MH−PPV molecules in multilayer organization. MH−PPV is apt to form a stable and transferable monolayer film. The adjacent conjugated main chains of MH−PPV in LB films are aligned in side-by-side parallel fashion and packed with the plane of its π system approximately perpendicular to the layer plane (H-aggregate structure). The long alkyl side chains are characterized by all trans-zigzag conformation and average tilt angle (26.5 ± 1.5°) obtained by means of both FTIR and SAXRD. The LB films of MH−PPV are well ordered with layer-by-layer structure and a d-space of 49.9 Å.