Abstract: The surface properties of hydroxy-terminated polystyrenes were investigated by Wilhelmy plate technique and sessile drop method. The results show that the static contact angles for water on the air-side surface and the advancing contact angles of the films were almost the same as the unfunctionalized polymer. However, the contact angles on the glass-side surface and the receding contact angles were found to decrease greatly. At the same time, it was found that the molecular weight distribution(PDI) of the polymer was an important factor to affect the surface dynamic behavior of hydroxy-terminated polystyrene. The advancing contact angles of the film with broad PDI decrease with increasing of temperature, and reach a minimum at 40 ℃, whereas that of narrow PDI polymer have not been affected by temperature. The similar result was obtained by heating the film against water. DMA results show that the loss modulus, storage modulus and tanδ of PS-OH-1 began to change sharply at 40 ℃ at which the minimum of contact angle appeared. The reason may be attributed to the polymer molecules with lower molecular weight segregating to surface, which result in molecules in surface layer having a higher activity. We speculate that the observed results about the minimum contact angle at 40 ℃ are associated with the enhanced molecular freedom on surface and changes in bulk structure such as crystallinity.

Key words: Dynamic contact angle, Molecular weight distribution, Hydroxy-terminated polystyrene, Surface property