Kendi Kendini Onarabilen Nanokompozit Hidrojel Sistemlerin Tasarımı, Sentezi ve Karakterizasyonu

Abstract

The main aim of the presented thesis is to design, synthesize and characterize self-healing nanocomposite hydrogels. Self-healing model is a biomimetic process that is adapted to the material by imitating it from nature. Self-healing polymers are used in many fields such as aviation, space, defense industry and biomedical materials. Many of these materials fall short in their self-healing capacity and self-healing ability over and over again. Thanks to the dual physical cross-linking and chemical cross-linking network in the structure of nanocomposite hydrogel systems, self-healing can be rearranged by dynamic bonds exchange. The use of Near Infrared (NIR) light to give these polymers self-healing properties and to trigger the self-repair mechanism is examined. Research is being carried out to develop the necessary mechanism for the NIR responsive nanocomposite hydrogel to repair itself over and over again. Self-healing nanocomposite hydrogel synthesis is carried out from acrylamide and maleic anhydride monomers in the presence of Laponit RD clay and gelatin by in-situ solution complex radical copolymerization method. HNT@Polydopamine material obtained by dopamine oxidative polymerization on the surface of Halloysite Nanotube (HNT) is used as a photothermal agent in order to response the nanogel system to Near Infrared (NIR) light and to provide self-healing. Physical and chemical cross-links presented in the nanogel system provide reversible deformation. In order to further increase its self-healing capacity, synthesis prescriptions are prepared with photothermal additives and nanocomposite hydrogel can repair itself with Near Infrared (NIR) light trigger is synthesized. Characterization and structure-property relations are carried out using spectroscopic methods such as Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), Hydrogen Nuclear Magnetic Resonance (H-NMR) and X-Ray Photoelectron Spectroscopy (XPS). Decomposition temperatures of the polymers are investigated by used with thermal analysis method such simultaneous Thermal Gravimetric Analysis-Differential Scanning Calorymetry (TGA/DSC) analysis. Dynamic Mechanical Analysis (DMA) results were obtained for the glass transition temperature and thermal transitions of the copolymer and NIR sensitive filler material. DMA results give the information about the surface morphology of the nanocomposites. Scanning Electron Microscope (SEM) Analysis was performed to obtain information about the surface porosity of the nanocomposites. Zeta potential and mobility measuring device (ZETA) test method is used for particle size and Zeta potential measurements. Swelling experiments were performed to find the cross-linking ratio of nanocomposite hydrogels. ATR-FTIR spectrum of the Poly(MA-co-AAm) copolymer, Halloysite Nanotube and Polydopamine synthesized on HNT surface and nanocomposite hydrogel was examined; the structure-property relationships are explained by characteristic peaks. Thermoanalytical results of the Poly(MA-co-AAm) copolymer were evaluated as the remaining inorganic phase due to potassium persulfate initiator groups for the remaining fraction without mass loss of about 19.3%. XPS analysis of HNT@Polydopamine sample is examined, the severe increase in the carbon (C1s) level proves that dopamine has undergone the polymerization on the HNT surface. Regarding the DMA analysis, as the temperature increases, a decrease in the storage modulus is observed. It proves the tendency of the storage modulus to decrease with the increase in temperatue, which is typical of thermoplastic matrix composites. When the nanocomposite hydrogel containing different amounts of HNT@Polydopamine is characterized by SEM, it is understood that the HNT@Polydopamine material has uneven edges and rough surface. Due to the photothermal property of polydopamine in the NIR-treated nanocomposite material, a self-healing structure was observed by converting light energy into heat energy. It has been proven that self-healable polymers over and over again can be an alternative for recycling and giving contribution to environment. There have been studies that the self-healing mechanism repeats more than once and the healing from the same place occurs more than once.

Keywords: Self-healing, nanocomposite, hydrogel, Near Infrared (NIR), cross-linking, copolymer/clay, smart polymers.