Synthesis and Characterization of Homo and Amphiphilic Block Copolymers of Poly(2-Vinylpyridine) Stabilized Metallic Nonoparticles

Abstract

This Ph. D. dissertation deals with the synthesis of metallic nanoparticles with P2VP homo- and block copolymers (BCP) as stabilizing agent, their characterization, and applications. As a summary of the research conducted during the course of Ph. D., a series of homopolymers of poly(2-vinylpyridine) and amphiphilic block copolymers of poly(2-vinylpyridine), including poly(2-vinylpyridine)-block-poly(methyl methacrylate) and polystyrene-blockpoly(2-vinylpyridine) were used to stabilize metallic nanoparticles (gold and silver). Polymers containing pyridine moiety have been utilized as a stabilizing agent for the metallic nanoparticles. Among them poly(2-vinylpyridine) (P2VP) is the excellent candidates because nitrogen atoms of the pyridine moiety have a strong affinity for the metal ions and metallic nanoparticles that restrains the aggregation of the metal nanoparticles through steric stabilization. Furthermore, P2VP prompts the reaction at ambient temperature and reduction of the particle size with the increase in its molar mass. AuNPs stabilized by P2VP ligands were designed to offer atomic level control and an efficient scale-up production through control of the molar mass of P2VP. Molar mass of the P2VP has enormous effect on the stabilization, size and size distribution of AuNPs. The reducing activity of P2VP increased with the increase in its molar mass. The P2VP stabilized AuNPs are evaluated for their stability and applications using UV-visible spectrophotometry, FTIR, DLS and AFM. Moreover, the drug encapsulation efficiency of P2VP-stablized AuNPs increased with the molar mass of P2VP. P(S-VP)-AgNPs were used as nanosensor for the rapid quantitative assay of pesticide, cartap. P(S-VP)-AgNPs and its interaction with cartap was studied using UV-visible spectroscopy, FTIR, zetasizer and AFM. The synthesized nanosensor is selective towards cartap in the presence of other interfering pesticides in real samples. The LoD of the nanosensor for cartap is far below already reported sensors for cartap. Furthermore, P(2VP-MMA)-AuNPs modified GCE electrode was used as a novel electrochemical sensor for nicotine. It was found that sensitivity of bare GCE is significantly enhanced by coating with P(2VP-MMA)-AuNPs. The P(2VP-MMA)AuNPs modified GCE is more sensitive towards nicotine and gave more intense electrochemical response with reference to bare GCE. In addition, the morphology of P(2VP-MMA) copolymer thin films was studied using AFM. It was observed that both P2VP and PMMA block lengths, total molar mass of block copolymer, solvent used for casting, and substrate play an important role in the morphology of block copolymer thin film. Gold nanoparticles incorporated with the polymer are completely shielded by P2VP chains and influenced the morphology of block copolymer organization by enlarging the polymer domain. Furthermore, surface roughness and thickness increased with the increase in molar mass of the block copolymers.