Wettability of hydrogels. I. Poly (2-hydroxyethyl methacrylate)

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Surface Science

Background:

• Poly(2-hydroxyethyl methacrylate) (PHEMA) is a widely used hydrogel in contact lens applications.
• Understanding the wettability of PHEMA is crucial for optimizing contact lens comfort and performance.
• Hydrogel wettability influences tear film stability and ocular surface interactions.

Purpose of the Study:

• To quantitatively assess the wettability of PHEMA hydrogel materials using water.
• To investigate the influence of water content and surface properties on PHEMA wettability.
• To compare contact angle measurements obtained from different goniometry techniques.

Main Methods:

• Contact angle goniometry was employed, utilizing both the sessile drop and captive air bubble techniques.
• Advancing and receding contact angles were measured to evaluate contact angle hysteresis.
• PHEMA gels with varying water content were prepared and analyzed.

Main Results:

• Water did not spontaneously spread on PHEMA gel surfaces, indicating limited wettability.
• Significant hysteresis was observed between advancing and receding contact angles.
• Water content did not significantly affect water wettability within the investigated hydration range.

Conclusions:

• PHEMA hydrogel surfaces exhibit complex wettability behavior, likely due to polymer chain reorientation.
• Surface structure and segmental mobility, influenced by preparation methods, are key factors in PHEMA wettability.
• Consistent differences between sessile drop and captive bubble methods suggest potential underlying phenomena beyond methodological artifacts.