Polymer brush-modified photopolymer network surfaces and their applications
Because of their important role in many areas of science and technology, polymer brushes have been extensively studied theoretically and experimentally. In the first part of my thesis, in order to understand the molecular weight behavior of polymer brushes, a new method to cleave polymer brushes were investigated. A new inimer (having both an initiator and monomer fragment) was synthesized. After growing polymer brushes from these inimers containing cleavable linkages, the polymer brush layers were characterized by various techniques. The brush chains were cleaved and collected, providing an opportunity to study and compare polymer grown in solution vs. polymer grafted from the inimer-inbedded surfaces. Molecular weight differences were determined since it has been assumed, but not confirmed, that polymers synthesized in both manners should have the same molecular weight.
Since growing a brush layer from a photopolymer (PP) layer is different than growing brushes from the surface directly, the first part of my thesis is dedicated to showing the differences between these two surfaces and how the PP network affects the brush growth with using different characterization methods such as neutron reflectivity and secondary ion mass spectroscopy. These studies helped to understand the characteristic behavior of the polymer brushes such as where the initiation occurs, how the inimer concentration affects on the photopolymer properties.
The next part of my thesis is about the possible applications of polymer brushes. We examined the antibacterial effects of –onium salts and enzymes attached to polymer brushes. It is already known that -onium salts can be used as antibacterial agents in solution. They can kill both Gram-positive and Gram-negative bacteria. In our case, polymer brushes were grown from the PP layer spin-coated on glass substrates, and we investigated their antibacterial effectiveness of these polymer brushes. Phosphonium salts and lysozyme were used as antibacterial agents. Lysozyme was chosen since it is biocompatible and can be used inside the body.
Lastly, azobenzene-containing photoresposive polymer brushes were prepared and the surface properties before and after UV exposure were observed. The surface wettability changes dramatically, and using only UV light is one of the safest and cleanest way to alter surface properties.