Formation and Characterization of Zwitterionic Hydrogels and Microgels via Photoinduced Polymerization: A Study on Carboxybetaine Methacrylamide and Poly (ethylene Glycol)-based Systems

This thesis investigates the formation and characterization of zwitterionic gels and microgels made by photoinduced polymerization, with a particular focus on Carboxybetaine Methacrylamide (CBMAA) as a key component. The research centers on gel samples composed of two types of monomers: CBMAA and Poly(Ethylene Glycol) Methyl Ether Methacrylate (MeOEGMA), enhancing the understanding of zwitterionic hydrogels and their potential applications, formation, properties, and characterization. The initial sections of the thesis provide a comprehensive introduction on granular hydrogels including details on microparticles fabrication methods, including extrusion fragmentation, batch emulsion, and microfluidic systems, to describe assembly processes and common applications. Moreover, an overview of CBMAA polymer is presented, highlighting its unique zwitterionic properties and chemistry. The polymerization reactions are examined, laying the groundwork for understanding the subsequent formation of hydrogels. The thesis examines various methods of hydrogel formation, with particular emphasis on PEG-based hydrogels, which are integrated into the study. The materials and methods section provides a detailed account of the experimental procedures implemented in this study. It outlines the synthesis methods of hydrogels, where the formation is photoinduced by ultraviolet (UV) radiation, utilizing various monomers and a particular polymer according to the specific technique employed. The characterization of hydrogels is conducted using various techniques, including photo Rheology, Spectroscopy, DSC (Differential Scanning Calorimetry), Equilibrium water content measurement, and Confocal imaging of microgels formed by batch emulsion. The application of these techniques is subsequently described, providing experimental results in the results and discussion section. The main investigated parameters are: strength and stiffness of hydrogels, gelation threshold, chemical structure and composition, thermal properties, phase transitions, hydrophilicity and water absorption. Finally, confocal imaging is applied, to visualize the microgels, providing insights into their morphology and structural characteristics. In conclusion, by aggregating and interpreting the results, a comprehensive discussion is provided on how the hydrogel's chemical composition influences its properties, with the future aim of better directing the use of these gels according to specific needs and fields.