Synthesis and characterization studies of organically soluble acrylic acid doped polydiphenylamine

Abstract

Polydiphenylamine (PDPA) doped with acrylic acid was synthesized by oxidative chemical polymerization. This is a new chemical polymerization method developed for the direct synthesis of emeraldine salt form of polydiphenylamine which exhibits remarkably improved solubility in a common organic solvent. These polymers have been characterized by the physical techniques such as UV-visible, FTIR, XRD and conductivity measurement. The results are discussed with reference to the H2SO4 doped polydiphenylamine. The use of functionalized acrylic acid (AA) made it possible to obtain the polymer in doped state with enhanced solubility in organic solvent such as N-methyl pyrrolidinone (NMP) and m-cresol directly without converting to emeraldine base form. The UV-visible spectra of acrylic acid doped PDPA in m-cresol showed a free carrier tail commencing at 950 nm, which may be attributed to secondary doping due to extended coil conformation. Whereas in NMP spectra excitonic peak at ~ 320 nm and 610 nm typical for emeraldine base form indicates that NMP dose hinders the doping ability of dopant. The FTIR spectra shows a broad and intense band at ~ 3400 cm–1 and 1150–1050 cm–1 in acrylic acid doped PDPA account for the higher doping level than H2SO4 doped polydiphenylamine polymers. This is further manifested by the X-ray studies and conductivity measurement. The X-ray diffractograms of acrylic acid doped polymer show an enhancement in the crystallinity indicating better ordered chain alignment. These results are well supported by the conductivity measurements, where the conductivity of acrylic acid doped polymers is greater than that of H2SO4 doped polymers.