Enhancing oxygen permeability and water content in silicone hydrogels through carboxylic acid and surfactant incorporation

Background

Silicone hydrogels are vital materials in fields like contact lenses, biomedicine, and electronic devices, prized for their unique properties including oxygen permeability and equilibrium water content (EWC). These features make them ideal for applications that require both breathability and moisture retention, enhancing their performance and comfort in various uses. Typically, enhancing the silicone content increases oxygen permeability but reduces EWC, creating a significant trade-off.

Methods

This study introduces an innovative approach using carboxylic acid and surfactant to address this challenge. The addition of carboxylic acid markedly boosts the EWC by increasing both freezable free water and bound water. Simultaneously, the surfactant enhances the connectivity within the silicone structure, mitigating the reduction in oxygen permeability and improving the material's ductility, which is often compromised by water absorption that restricts the motion of the silicone chains.

Significant findings

With these modifications, the silicone hydrogel achieves approximately 97 % transmittance at 550 nm, with oxygen permeability reaching 100.4 barrer and EWC at 58.4 %, representing improvements of 11.3 % and 61.3 %, respectively, compared to the original material. These results exceed many of the enhancements in silicone hydrogels previously reported in the literature.