INVESTIGATION OF ULTRATHIN FILMS OF PROCESSABLE POLY(O-ANISIDINE) CONDUCTING POLYMER OBTAINED BY THE LANGMUIR-BLODGETT TECHNIQUE

Langmuir films of poly(o-anisidine) conducting polymer in its undoped (emeraldine base) and doped (emeraldine salt) forms have been obtained by the proper selection of subphase. pi/A isotherms,quartz crystal mi crobalance, Brewster angle microscopic, and UV-vis-near IR spectroscop ic measurements provided evidence concerning the effects of HCl doping on the polymer molecular organization as well as film properties. The analysis underlines that the presence of dopant induces structural an d conformational changes on the polymer structure from the emeraldine base to emeraldine salt, so causing a different arrangement of the mol ecules at the air/water interface. Moreover, the emeraldine base form of poly(o-anisidine) Langmuir films evidenced less compressibility, as suggested by the presence of aggregates at high surface pressures, an d a lower collapse surface pressure with respect to the emeraldine sal t one. The investigation of the Langmuir film formation by the Brewste r angle microscopy made it possible to support the previous experiment al results and to image directly two (2D)-three (3D) dimensional trans formations, which occurred by overcompressing beyond the limiting dens ities of close-packed 2D films, namely, collapse pressure. The recorde d optical spectra revealed the development of polarons and bipolarons due to inclusion of the dopant in the polymer backbone and also provid ed an estimation of the poly(o-anisidine) bandgap.