Synthesis and Characterization of Novel Polyamidoximes, Polyamides, Poly(amide-imide)s and Poly(ester-amide)s and their Applications for the Removal of Metal Cations from Aqueous Solutions

Abstract

Novel polyamidoximes, poly(amide-imide)s, poly(ester-imide)s along with crosslinked polyamidoximes and polyamides have been reported in this thesis. The foremost goal of the current research endeavor is to design some new adsorbents dealing with adsorption of heavy metal cations, with excellent thermal resistance. The designed monomers (2,6-bis(4-chloroformylphenoxy)benzonitrile, 2,6-bis(4aminophenoxy) benzonitrile, 5-(5-carboxy-1,3-dioxoisoindolin-2-yl) isophthalic acid)bearing pre-formed linkages were synthesized and employed for the novel polymer synthesis. Monomer synthesis was confirmed using FT-IR and NMR spectroscopic analysis while polymer formation confirmed by molecular weight (GPC), XRD and TGA data study. Condensation polymerization was used for the fabrication of polymeric materials. In cross-linked polymers much better crystallinity in addition to boost in thermal resistance was noted. The incorporation of various linkages with more electronegative centers provided polymers with high molecular weights, improved crystalline nature, advanced thermal stability and efficient adsorption capacity. The effect of numerous groups towards adsorption capacity of Cd+2 and Pb+2 was scrutinized following a thorough study of adsorption by batch process. Effects of variable pH, contact time, amount of adsorbent and concentration of adsorbate were deliberately studied with a maximum uptake at pH 6 and 3h of contact time. AAS provided information about the metal ion concentration in the media before and after the adsorption process. The adsorption process was found to be favorable following the Langmuir adsorption isotherm as compared to Freundlich, thus giving an insight to monolayer adsorption over a range of concentration studied. Their ease in formation, high molar mass, heat stability and metal binding ability depict their compliance, rendering them a key material in future polymer science.