Uyarana duyarlı polimerlerin kendiliğinden yapılanarak oluşturduğu yapılar ve bu yapıların kontrollü salınım uygulamaları

Self-assembled nanostructures of stimuli-responsive polymers combine the advantages of responding to environmental changes with specific properties of the nano-systems. Effect of various physicochemical factors on self-assembly process is important in designing nano-systems for controlled release applications. This thesis reports the formation and controlled release applications of hydrogen-bonded (H-bonded) self-assembled structures (layer-by-layer (LbL) films or fibers) consisting of a thermo-responsive polymer, poly(2-ethyl 2-oxazoline) (PEOX), and pH-responsive molecules, tannic acid (TA) or malonic acid (MA). pH-responsive H-bonded LbL assemblies of PEOX and TA restructure in acidic phosphate buffer into pH-responsive fibers. Since H-bonds between PEOX and TA are stable in acidic solutions, the restructuring was attributed to hydrophobicity increase of PEOX in time by H2PO4- ions. A systematic investigation of the influence of Hofmeister series of salts on the properties of PEOX/TA multilayers was presented. pH stability of the films increased and the film thickness decreased with the anion type in Hofmeister series in direction from kosmotropic (dehydration of polymer chains) to chaotropic anions (direct binding of ion on the chain). PEOX/TA multilayers as controlled release platforms were demonstrated by using Rhodamine 6G dye molecule. Release was pH and temperature-responsive depending on the ionization of TA and cloud point temperature (Tcp) of PEOX. Effect of chemical structure of H-accepting polymer on release was studied by forming poly(N-isopropylacrylamide) (PNIPAM)/TA multilayers which exhibited faster release due to more hydrophobic structure. Hollow fibers of PEOX/MA formed in aqueous solutions by slow self-assembly. At pH2, hollow fibers formed by H-bonding while at pH4, electrostatic bridging of PEOX chains by MA was dominant. Fiber formation was temperature-responsive depending on Tcp of PEOX. The effect of three salts (Na2CO3, NaCl, NaSCN) on fiber formation was studied. The potential of fibers in controlled release applications was demonstrated by the release of Ciprofloxacin, a broad-spectrum antibiotic, at pH7.4.