Silicone hydrogels haves been widely utilized in many in ophthalmic and other biomedical applications due to the its comfort of hydrogels, their excellent biocompatibility, high oxygen permeability and transparency. For use as a contact lens, the silicone hydrogel with interacts with the tear film, cornea, and eyelid;, thus surface properties of the gel are crucial to be considered. The highly oxygen permeabilitye performance of the silicone hydrogel contact lens materials mainly relies on the incorporationng of the siloxane functional groups., Hhowever these groups are extremely mobile and surface active, which can result in an increase in the of lens surface hydrophobicity, as well as protein and lipid deposition. Therefore, there is a need for surface modification of silicone hydrogel contact lenses. Otherwise users may might have to choose to decrease the frequency and length of wearing duration of silicone contact lenses due to dryness or bio-fouling related issues. A novel biomimetic methacrylate monomer which contains a phosphorylcholine group, 2-mMethacryloyloxyethyl pPhosphorycholine (MPC) is was grafted onto the surface of novel silicone hydrogel materials surface to create a thick hydration layer in order to enhance the protein resistance and surface wettability. Low temperature air plasma has beenwas chosen to initiate grafting polymerization of MPC monomers onto silicone hydrogel substrates. Hydrogels were treated with plasma and exposed to air flow to yield hydroperoxides on the surface; the, and peroxides group acted as a photo-initiators for further thermal MPC grafting polymerization. After surface modification, the silicone hydrogels were characterized by XPS and ATR-FTIR to confirm the structure and elemental composition. A significant amount of phosphorus element was found shown on the XPS spectra of the modified materialsum,, demonstrating that so the MPC monomers were successfully grafted onto the gel surface. According to water contact measurement results, the modified samples possessed very hydrophilic surfaces, with advancing angles of about 27°, while compared the unmodified samples at around 110°. After surface grafting, between a around 20% and to 50%’s reduction in protein deposition was also observed, which aligned with water contact angle results. Other properties such as oxygen permeability, transparency, water equilibrium, and elastic modulus remained unchanged after the air plasma exposure and thermal MPC polymerization. / Thesis / Master of Applied Science (MASc)

<p> Poly (dimethyl siloxane) (PDMS) has been widely used as a biomaterial in ophthalmic and other applications due to its good compatibility, high mechanical strength and excellent oxygen permeability and transparency. For use as an artificial cornea, contact lens and in other applications, modifications are necessary to improve glucose permeability and wettability for cell and tear protein and mucin interactions through modification with hydrophilic functional groups or polymers. Poly (N-isopropyl acrylamide) (PNIPAAM) is a biocompatible and hydrophilic polymer that has been extensively studied in controlled drug release applications due to its lower critical solution temperature (LCST) phenomenon. In this study, a composite interpenetrating polymer network (IPN) of PDMS and PNIPAAM was formed to generate material with reasonable oxygen and glucose permeability as well as improved wettability and mechanical properties compared to the PDMS and PNIPAAM homopolymers.</p> <p> Semi-IPNs, with low water uptake and mechanical strength, were found not to be suitable as biomaterials. Vinyl terminated PDMS/PNIPAAM IPNs had reasonable water uptake and excellent tensile stress and strain, but low glucose permeability (< 10^-10 cm^2/s). Hydroxyl terminated PDMS/PNIPAAM IPNs (PDMS-OH IPN) were successfully synthesized with reasonable mechanical properties and significantly higher glucose permeability (~10^-7 cm^2/s). Curing the PDMS-OH film with solvent was found to improve glucose transport.</p> <p> The presence of PNIPAAM in the composite networks was confirmed by FT-IR and Differential Scanning Calorimetry (DSC). Transmission Electron Microscopy (TEM) images verified the structure of interpenetrating networks. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) and X-ray Photoelectron Spectroscopy (XPS) suggested that PNIPAAM was also present on the surface and this translated to increased roughness compared with the PDMS control as determined by AFM. The LCST phenomena still remained in the IPN, although the change was not as abrupt as with pure PNIPAAM. These results suggest that the copolymer may be useful as an ophthalmic biomaterial and for controlled drug release applications.</p> / Thesis / Master of Applied Science (MASc)