Surface characterization of poly(hydroxyethyl methacrylate) and related polymers. I. Contact angle methods in water

The characterization of the gel‐water interface is considered, particularly with respect to obtaining the interfacial free energy between the gel and water, γ utilizing contact angle data. The question of contact‐angle‐induced deformation of the three‐phase region is examined and visual documentation of such deformation is presented. Air in water and octane in water contact‐angle data are used to estimate γdsv γpsv γsv, and γsw for the gel‐water interface as a function of bulk water fraction in the gel. It is shown that γ °0 ± 5 erg/cm2 when the bulk water fraction is greater than 0.2. All interfacial parameters determined appear to reach a constant value at a bulk water fraction of about 0.4. These results are for poly(hydroxyethyl methacrylate), poly(methoxyethyl methacrylate), poly(dihydroxypropyl methacrylate), and selected copolymers at 25°C in distilled water.