Polymer nanocomposites for phthalate detection remediation and metamaterial applications

Abstract

The thesis, titled "Polymer Nanocomposites for Phthalate Detection, Remediation, and Metamaterial Applications," is a product of our strong motivation to expand the structure-defining capabilities of polymers for environmental and dielectric applications. The central objective was to address phthalate detection and remediation issues and fill critical gaps in metamaterial technology for extremely low-frequency applications. The thesis comprises eight chapters, beginning with an introductory overview in Chapter 1 and an overview of experimental techniques in Chapter 2. Chapters 3 to 7 are working chapters, presenting findings and conclusions. Chapter 8 provides a comprehensive summary, and Chapter 9 gives our recommendations for future research works on the thesis topic. One of the significant advancements made in this thesis is phthalate detection using flexible noble metal-free SERS substrates. The substrates based on BaTiO3, PMMA_BaTiO3, and PMMA_SrTiO3 have been engineered and customized to detect dimethyl phthalate (DMP), diethyl phthalate (DEP), and Di(2- ethylhexyl) phthalate (DEHP), respectively. Innovative synthesis methods, combining modified low-temperature sol-gel routes with in-situ polymerization, produced substrates with the essential "hotspots" for amplifying Raman signals. Microstructuring within the substrates facilitates the trapping of probe molecules and enhances charge transfer-mediated chemical enhancement in Raman signals. The findings underscore the substrates' ability to detect accurately without spectral interference, essential for differentiating between substrate and probe molecules. In the realm of water remediation, this thesis focuses on removing Dimethyl Phthalate (DMP) using Zinc Oxide-incorporated Polypyrrole (PPy_ZnO) polymer nanocomposites synthesized via oxidative polymerization. The structural integrity, cooperative effect of slit-like micropores and the conjugated benzene rings of PPy_ZnO led to effective removal of DMP across a wide range of concentrations in aquatic environments.In the domain of metamaterial applications, this research addresses the gap in metamaterials suitable for the extremely low-frequency regime. Two ternary composites were crafted by integrating a PMMA matrix with two distinct filler combinations: AC_ZnO and Graphite_CaTiO3. Microstructuring mediated by the PMMA voids beyond the percolation threshold facilitated the formation of interconnected 3D conducting networks, enabling the transition to negative permittivity. Interestingly, replacing metallic fillers with ceramic counterparts drastically changes the order of magnitude of permittivity values from 104 to 108. The selection of filler candidates and their concentrations played a crucial role in fine-tuning negative permittivity for the ELF regime. In summary, this thesis has made scientific contributions to managing environmental pollutants through their detection and removal. Also, it could effectively place a nanocomposite, which could fill the need for metamaterials working in the ELF regime- catering to communication technologies. For its social significance, the developed composites and their scientific understanding contribute to sustainable development goals by promoting cleaner environments and safer living conditions, aligning with global efforts to mitigate pollution and enhance technological capabilities for societal benefit.