Browsing by Subject "carboxylated poly(ethylene imine)s"

In this master’s thesis, linear zwitterionic poly(ethylene imine) methyl-carboxylates (l-PEI-MCs) were synthesized through a four-step synthesis. The synthesis started with the polymerization of 2-ethyl-2-oxazoline (EtOx) monomers into poly(2-ethyl-2-oxazoline) (PEtOx) homopolymers with polymerization degree of 50 and 100. Living cationic ring-opening polymerization (LCROP) enabled a good control over the molecular weights. Subsequently, the side chains of PEtOxs were cleaved off by acidic hydrolysis. This resulted in linear poly(ethylene imine)s (l-PEIs) bearing a secondary amine group in repeating units of the polymer chain. These amine units were then functionalized with methyl-carboxylate moieties by first introducing tert-butyl ester functionalities to l-PEI chains, and subsequently cleaving off the tert-butyl groups. The final polymer is a polyzwitterion, featuring both an anionic carboxylate and a cationic tertiary amine group within a single repeating unit. Polymers produced in each step were characterized via 1H-NMR and FT-IR spectroscopy and their thermal properties were analyzed by differential scanning calorimetry (DSC). The molecular weights and dispersities (Ð) of PEtOx polymers were additionally estimated by gel permeation chromatography (GPC). Via 1H-NMR, the degree of polymerization for PEtOxs and the hydrolysis degree for l-PEIs were determined. FT-IR gave a further insight into the structures of polymers, successfully confirming the ester functionality of modified l-PEI. The disappearance of the tert-butyl proton signal in 1H-NMR spectrum after deprotection verified the successful removal of tert-butyl groups, resulting in the final product with methyl-carboxylate functionalities. By DSC, different thermal transitions, i.e., glass transition (Tg), melting (Tm) and crystallization (Tc), were observed, and the effects of molar mass and polymer modifications on these transitions were being investigated. The state of the art explores the literature regarding synthesis and properties of poly(2-oxazoline)s (POx), poly(ethylene imine)s (PEIs), and polyzwitterions. The theory behind living cationic ring-opening polymerization of 2-oxazolines and acidic hydrolysis of POxs is described. Different post-polymerization modification strategies to functionalize PEIs are being discussed. In addition, possible applications for each of these polymer classes are shortly outlined.