Preparation and properties of silicone hydrogel contact lens based on PDMS-PU macromer

Abstract

The production of highly oxygen-permeable hydrogel materials is usually accomplished by incorporating highly oxygen-permeable silicon chain segments into the hydrogel system. Silicone hydrogels are prepared using two types of monomers: small molecule siloxanes and macromeric siloxanes. However, while small-molecule siloxane monomers have limited improvement in oxygen permeability, macromer siloxane monomers such as polydimethylsiloxane (PDMS) have better oxygen permeability but are poorly compatible with hydrophilic monomers, and direct copolymerization is not able to obtain transparent and homogeneous materials. To address this issue, PDMS was modified to synthesize polydimethylsiloxane-polyurethane (PDMS-PU) macromers, which were characterized by GPC and 1H NMR. UV-initiated free-radical polymerization was used to prepare silicone hydrogel contact lenses by copolymerizing PDMS-PU macromer, bis(trimethylsiloxane)methylsiliconpropylglycerol methacrylate (SIGMA), DMA, NVP, PEGMA, and HEMA in various ratios. The resulting copolymers were characterized using various methods including thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), refractive index (RI), equilibrium water content (EWC), oxygen permeability (Dk), optical transparency, contact angle, mechanical properties, protein deposition, and cytotoxicity. The results showed that the silicone hydrogels were resistant to protein deposition and noncytotoxicity, the Dk could be increased from 65 to 91 barrers when the percentage of PDMS-PU was increased from 0 to 20 wt%, and the properties of the synthesized silicone hydrogel polymers, such as RI, EWC, and oxygen permeability, Dk, showed a linear dependence on the percentage of PDMS-PU. This study suggests a possible idea for the preparation of highly oxygen permeable silicone hydrogel contact lens materials with tunable properties.

Graphical abstract