Langmuir and Langmuir-Blodgett films of polyaniline.

Author(s)

Antonio Riul Júnior

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Instituto de Física de São Carlos (IFSC/BT)
• Defense date: 1998-05-19

Examining board members

Osvaldo Novais de Oliveira Junior; Roberto Mendonça Faria; Wania da Conceição Moreira; Elisabeth Andreoli de Oliveira; Maria Elisabete Darbello Zaniquelli

• Advisor: Osvaldo Novais de Oliveira Junior

Abstract

A study has been made of composite Langmuir and Langmuir-Blodgett (LB) films of polyaniline (PANi), and a polyaniline oligomer (l6-mer polyaniline), with cadmium stearate (CdSt). The monolayers studies pointed to a phase separated system containing the polymer (or the 16-mer) and CdSt, with no mixing at the molecular leveI, although the relative contents of PANi and 16-mer in the solution have a strong influence on the monolayer stability. UV-vis, FTIR, X-ray difIraction (XRD), electrical conductivity, ellipsometry, optical microscopy and surface potential measurements were used in the LB film characterization. UV-vis results have shown a uniform transfer, with the as deposited films in the undoped state. FTIR results confirmed the presence of CdSt and undoped polyaniline (and 16-mer) in the transferred LB films, corroborating the UV-vis results. XRD has shown separated domains of CdSt and PANi (l6-mer also) in the LB films. Ellipsometry data indicated a thickness of 25 &#197 per deposited layer. The high uniformity in these mixed LB films was confirmed by optical microscopy and surface potential measurements. The electrical conductivity was approximately 10-4 to 10-5 S.cm-1 for both PANi and 16-mer. Mixed PANi/CdSt films were also exposed to X-ray irradiation. After a given dose rate there is a red shift in the UV-vis spectra from the 600 nm region to the 800 nm region, similar to the usual acid doping process observed in polyaniline. Humidity effects have a strong influence on the doping process. A comparison is made of the conductivity measurements made here with those reported in the literature. (AU)