Morphology controlled synthesis of polyaniline nanostructures and its nanocomposites using swollen liquid crystals as templates (PhD)

Abstract

Polymers are generally known for their insulating properties. But intrinsically conducting polymers (ICPs) is the class of organic conjugated polymers that can conduct electricity. ICPs find promising applications in different fields such as in sensors, electronic devices, integrated circuits, catalysis, energy storage, memory devices etc. Polyaniline (PANI) is one of the most studied among the ICPs. PANI is more interesting due to its good environmental stability, ease of synthesis and controllable electrical conductivity through protonation/deprotonation. Properties of PANI can be tuned by nanostructuring and nanocomposite formation also and improved performance can be obtained. Exploration of novel methods for the synthesis of PANI nanostructures and the nanocomposites is thus an important research area and this is the major theme of the present thesis. Preparation of PANI nanostructures and their nanocomposites using swollen liquid crystals (SLCs) as ‘soft’ templates is presented in the thesis. SLCs are a class of lyotropic liquid crystals that is usually formed from a mixture of water, oil, surfactant and co-surfactant. The aspects such as diameter of the micelles and the distance between them can be varied in SLCs and hence the name. It has been shown in the past that the SLCs can be used as versatile templates for the synthesis of a variety of noble metal nanostructures. A general method for preparing spherical and one dimensional nanostructures of PANI and its nanocomposites by using SLCs as templates has been developed and presented in the thesis. Controlling the morphology of PANI and its nanocomposites with Au, Pt, Fe3O4 and pristine graphene has been demonstrated using SLCs as templates in the present study. The prepared nanomaterials were thoroughly characterized using advanced characterization techniques. The PANI nanostructures and its nanocomposites were found to have interesting applications in sensing, catalysis and environmental remediation. The present thesis entitled ‘Morphology controlled synthesis of polyaniline nanostructures and its nanocomposites using swollen liquid crystals as templates’ contains eight chapters. Chapter 1 provides an overview of ICPs, PANI, its nanostructures and nanocomposites, SLCs and their use as ‘soft’ templates. Chapter 2 describes an approach for the synthesis of PANI nanostructures by confining aniline in the oil phase of SLCs. Chapter 3 mainly focuses on the utility of the aqueous phase of SLCs for the synthesis of PANI nanostructures. Synthesis of Goldcore-Polyanilineshell composite nanowires and their SERS and catalytic activities is described in chapter 4. Controlling the morphology of PANI-Pt nanocomposites using SLCs as templates is discussed in chapter 5. In chapter 6, synthesis of polyaniline-iron oxide nanocomposites is discussed. Chapter 7 is based on the preparation of a unique pristine graphene-PANI nanocomposite using SLCs. Chapter 8 presents the key findings of our research work and the future scope of the present work.