Spectroscopic, thermal and electrical properties of sulphonic acids doped poly(o-anisidine) and their application as humidity sensor

Abstract Poly(o-anisidine), P(o-anis) doped with camphor sulphonic acid (CSA) and p-toluene sulphonic acid (p-TSA) was synthesized by in situ chemical polymerization method using ammonium persulphate as an oxidizing agent. This is a single step polymerization process for the direct synthesis of emeraldine salt phase of the polymer. The polymers were characterized by using UV–vis and FT-IR spectroscopy, TGA and conductivity measurements. Formation of mixed phases of polymer together with conducting emeraldine salt phase are confirmed by spectroscopic techniques. Thermal analysis shows that poly(o-anisidine) has three stage decomposition pattern similar to unsubstituted polyaniline. The lower conductivity in poly(o-anisidine) compared to polyaniline is due to the cumulative steric as well as electronic effects of the bulky methoxy substituent present on the benzene ring. High temperature conductivity measurements show ‘thermal activated behaviour’. The change in resistance with respect to % relative humidity (RH) is observed, when pressed pellets of the polymer were exposed to the broad range of humidity (ranging between 20–100% RH).

[1]  S. Im,et al.  X-ray photoelectron spectroscopy study of electrically conducting polyaniline/polyimide blends , 2000 .

[2]  M. Leclerc,et al.  Synthesis and characterization of substituted poly(anilines) , 1989 .

[3]  R. Aiyer,et al.  Charge transfer complex-forming dyes incorporated in solid polymer electrolyte for optical humidity sensing , 2001 .

[4]  K. Ogura,et al.  Investigation of Some Physicochemical Properties of Camphor Sulfonic Acid (CSA)-Doped Poly(o-anisidine) (PoAN) and CSA-Doped PoAN/ABS Composites , 1999 .

[5]  Antonio J. Ricco,et al.  Resistance of polyaniline films as a function of electrochemical potential and the fabrication of polyaniline-based microelectronic devices , 1985 .

[6]  S. Joo,et al.  Resistive humidity sensor using polyelectrolytes based on new-type mutually cross-linkable copolymers , 2003 .

[7]  K. Ogura,et al.  Thermogravimetric/Mass and Infrared Spectroscopic Properties and Humidity Sensitivity of Polyaniline Derivatives/Polyvinyl Alcohol Composites , 1998 .

[8]  G. Casalbore-Miceli,et al.  Humidity sensors based on polymer solid electrolytes: investigation on the capacitive and resistive devices construction , 2001 .

[9]  M. Leclerc,et al.  Steric and electronic effects in methyl and methoxy substituted polyanilines , 1993 .

[10]  Joseph R. Stetter,et al.  Humidity sensing properties of Nation and sol-gel derived SiO2/Nafion composite thin films , 1997 .

[11]  Ernest Bracken.  Combating humidity ‐ the hidden enemy in manufacturing , 1997 .

[12]  Masaharu Nakayama,et al.  The humidity dependence of the electrical conductivity of a solublepolyaniline–poly(vinyl alcohol) composite film , 1997 .

[13]  R. Aiyer,et al.  Novel dye+solid polymer electrolyte material for optical humidity sensing , 2001 .

[14]  Alan G. MacDiarmid,et al.  Polyaniline: Electrochemistry and application to rechargeable batteries , 1987 .

[15]  H. Ishikawa,et al.  Electrical conductivity of annealed polyaniline , 1993 .

[16]  A. Contractor,et al.  Applications of conducting polymers as sensors , 1994 .

[17]  Rahul Patil,et al.  Effect of protonation media on chemically and electrochemically synthesized polyaniline , 2000 .

[18]  M. Kulkarni,et al.  Spectroscopic, transport, and morphological studies of polyaniline doped with inorganic acids , 2004 .

[19]  M. Kulkarni,et al.  Studies on chemically synthesized organic acid doped poly(o-toluidine) , 2005 .

[20]  S. Umare,et al.  Studies on poly(o-methoxyaniline) , 1992 .

[21]  M. Kulkarni,et al.  Comparative studies of chemically synthesized polyaniline and poly(o-toluidine) doped with p-toluene sulphonic acid , 2004 .

[22]  M. Kulkarni,et al.  Synthesis and characterization of polyaniline doped with organic acids , 2004 .

[23]  Epstein,et al.  Transport studies of protonated emeraldine polymer: A granular polymeric metal system. , 1987, Physical review. B, Condensed matter.

[24]  M. Leclerc,et al.  Structure-property relationships in polyaniline derivatives , 1993 .

[25]  M. Koseki,et al.  Polyaniline as an electrode of rechargeable battery , 1989 .