Design and synthesis of poly(2-oxazoline)-derived adsorbent polymers and hybrid nanomaterials for water pollutant removal

Water pollution caused by organic and inorganic contaminants represents one of the most pressing environmental challenges, urgently necessitating the development of efficient, selective, and reusable adsorbent materials. The objective of this Doctoral Thesis is to design, synthesise, and apply novel poly(2-oxazoline)-based materials capable of selectively removing different classes of pollutants with high efficiency and reusability. Poly(2-oxazoline)s (POxs) were chosen as the central polymeric platform due to their excellent biocompatibility and versatile chemical functionality, particularly their tunable side chains, which enable tailored interactions with a wide range of contaminants. Among these polymers, poly(2-(3-aminopropyl)-2-oxazoline) (PAmOx) and poly(2-isopropyl-2-oxazoline) (PiPOx) were selected as key building blocks because they provide complementary functionalities. PAmOx contains protonatable amine groups that facilitate strong interactions with charged and polar pollutants, whereas PiPOx remains hydrosoluble at ambient temperature while bearing isopropyl side chains capable of engaging in hydrophobic interactions, making it suitable for the adsorption of nonpolar organic contaminants. These two different POxs were employed throughout this work as functional components in three main families of hybrid adsorbents: (i) molecularly imprinted polymers (MIPs) for the selective uptake of pharmaceuticals; (ii) inorganic nanoparticles (NPs) coated with functional POxs shells, designed for the removal of both organic contaminants (Fe₃O₄ NPs) and heavy metals (Fe₃O₄ and silver NPs); (iii) chitosan-based composite membranes incorporating PiPOx-functionalized silica NPs for the adsorption of organic dyes. MIPs based on PAmOx were prepared for the selective removal of Ibuprofen, exhibiting markedly enhanced adsorption capacities, favourable kinetics, and high selectivity compared to non-imprinted polymers. Their performance was further validated in natural lake water samples. To extend the range of contaminants addressed, multifunctional hybrid materials were subsequently developed through the surface functionalisation of Fe₃O₄ nanoparticles with poly(2-oxazoline) coatings. PAmOx-functionalised nanoparticles showed an increased affinity toward organic pollutants, whereas PiPOx-coated nanoparticles demonstrated strong selectivity for heavy metals, particularly Pb²⁺, highlighting the decisive role of polymer chemistry in governing pollutant specificity. In addition, a further class of nanomaterials, Ag@POx, was obtained via the covalent grafting of POxs onto silver nanoparticles. These systems proved highly effective in capturing Pb²⁺ and Cd²⁺, with spectroscopic analyses revealing distinct metal–surface interaction mechanisms. Finally, chitosan–silica nanoparticle–PiPOx bio-based hybrid membranes were explored for the removal of the dye Methyl Red, demonstrating how natural and synthetic polymeric components can be rationally combined to form multifunctional architectures with enhanced adsorption performance. In summary, this work presents an integrated and versatile strategy for water purification, encompassing POx-based MIPs, magnetic hybrid materials, metallic nanocomposites, and functional membranes capable of addressing a broad spectrum of 2 contaminants. Overall, it highlights the potential of poly(2-oxazoline)s as a modular and highly tunable platform for the development of sustainable, selective, and scalable technologies in environmental remediation.