WILHELMY PLATE MEASUREMENTS ON POLY(N-ISOPROPYLACRYLAMIDE)-GRAFTED SURFACES

Polystyrene surfaces have been modified by poly(N-isopropylacrylamide) (PIPAAm) grafting. Beside observing the adhesion and the effect of lo w-temperature treatment on anchorage-dependent cells, the wetting beha vior of PIPAAm-grafted surfaces was studied by dynamic contact angle m easurement by Wilhelmy microbalances. Measurements were performed in w ater at different temperatures and at different speeds of immersion. C ontact angle behavior has been explained in terms of heterogeneity of the surfaces, using a slightly modified hysteresis graph. The apparent inversion of advancing and receding contact angles shown at high spee ds of immersion has been analyzed in terms of kinetic effect, and it i s underlined the lack of a similar critical approach in existing liter ature data.