DYNAMIC CONTACT-ANGLE MEASUREMENT OF TEMPERATURE-RESPONSIVE SURFACE-PROPERTIES FOR POLY(N-ISOPROPYLACRYLAMIDE) GRAFTED SURFACES

We have investigated temperature modulation of surface properties for hydrophilic/hydrophobic changes using poly(N-isopropylacrylamide) (PIP AAm). Two types of PIPAAm were used as surface modifiers: an end-funct ionalized PIPAAm with a carboxyl end group and a poly(IPAAm-co-acrylic acid) copolymer. By means of dynamic contact angle measurements in wa ter, the wettability of terminally polymer grafted surfaces using end- functionalized PIPAAm with a carboxyl end group were compared with tha t of multipoint polymer grafted surfaces using PIPAAm copolymers conta ining carboxyl groups along the polymer chain. Each PIPAAm grafted sur face showed completely hydrophilic properties under 20 degrees C. Alth ough multipoint grafted surfaces demonstrated surface property changes near 24 degrees C, the extent of decrease in the hydrophilic property was small compared to that of the terminal grafted surfaces. Terminal grafted surfaces demonstrated hydrophilic/hydrophobic surface propert y changes at 24 degrees C with small temperature increases. The value of cos theta changes from 0.63 at 20 degrees C to 0.05 at 26 degrees C . Temperature-responsive surface property changes which terminal graft ed surfaces demonstrated were more rapid and significant than that of multipoint grafted surfaces;demonstrated. These features were suggeste d to be due to more effective restrited conformational freedom for PIP AAm graft chains which influence polymer dehydration and hydrogen bond ing with water molecules.