Preparation, Properties And Formation Mechanism Of Nano-lamellar Polyaniline And Its Nanocomposite From Lyotropic Liquid Crystalline Solutions

Polyanilines (PANIs), a typical class of conducting polymers, have relatively high electric conductivity, reversible doping/dedoping behaviour and excellent environmental stability. More importantly, micro-and nano-structured PANIs and their composites, have great potential applications in fields involving sensors, electronic devices, and information storage materials and so on due to their remarkable electric, magnetic and optical properties.In this paper, PANI lamellas with an average interlamellar distance of 3.4 nm were prepared from a nematic discotic (ND) lyotropic liquid crystal (LLC) system. Specifically, the following work was carried out:(1)The mechanism of the nucleation stage of the polymerization of aniline in ND LLC solution was characterized by NMR techniques taking into the anisotropic feature of the LLC systems. Accordingly, a series of variable temperature (VT)13C NMR experiments were carried out. On the basis of NMR experiment, it is safe for us to derive that:â‘ small SDS ellipsoidal disks have a strong propensity to coalesce with one another, leading to larger circular disks with more uniform disk-sizes at elevated temperature;â‘¡anilines,with a more rigid character, locates at the vicinity of the head groups domain of SDS species at low concentration, whereas they can penetrate into the SDS hydrophobic domain and becomes more mobile at increased concentration or high temperature;â‘¢in situ monitoring of the reaction in ND LLC show that the polymerization includes two stages. Initially, the nucleation occurs within the hydrophobic domain of SDS micelles and leads to the formation of the oligomeric PANI.Subsequently, these species fall down from the SDS hydrophobic domain to the interlayer, commencing the further chain growth reaction.(2) The fashion of stirring plays an important role on the structure and further on the properties of the prepared PANIs. An average distance of 3.4 nm is favorable for samples with and without stirring during the preparation, while a shorter one of 1.4 nm is preferable when the system was stirred only during the period of the addition of oxidant. Additionally, lamellar PANIs were in partially doped states through in situ doped process, although all these reactions were carried out at non-acidic conditions. The doping level of PANI was improved for sample prepared with stirring. Moreover, the lamellar PANI (with stirring during the preparation) displays a specific capacitance of 560 F/g at a current density of 0.4 A/g. It should be noted that capacitance retention of 86.7% at the current density range of 0.4 to 4.0 A/g can be achievable for our system with stirring all along. (3)Lamellar TiO2/PANI composites were prepared by hydrolyzing tetrabutyl titanate in ND LLC system. The interlayer distance is increased to 4.4 nm after loading TiO2, and the distribution of the interlayer become much wider. Finally, as high as 36.3% (weight%) of rutile TiO2 can be introduced into the polymer matrix, the crystallinity of PANI chains is improved.Furthermore, PANI and TiO2/PANI composite with layered-structure were also successfully synthesized from SDS solution with suitable concentration.