Surface Tension and Surface Dilatational Elasticity of Associating Hydrophobically Modified Polyacrylamides in Aqueous Solutions

Abstract

The effects of the variation of different parameters in some hydrophobically modified polyacrylamides in aqueous polymer solution on their surface properties have been investigated. Two different hydrophobes, N,N-dihexylacrylamide (DiHexAM) and N-(4-butylphenyl)acrylamide (BPAM), have been used; the former was most extensively investigated. The molecular weight (50 000−1 000 000), amount of hydrophobes (0.5−2 mol %), and block length of the hydrophobic groups (1−7 units) have been varied. The dynamic surface pressure has been measured by means of drop shape analysis of a sessile bubble, and the surface dilatational elasticity and viscosity have been obtained during the adsorption process by the oscillating bubble technique. Π−A isotherms of the adsorbed polymers have also been measured by using compression and decompression cycles on the sessile bubble. All the hydrophobically modified polymers show surface activity, but the adsorption rate is very low; it usually takes more than 24 h to obtain surface pr...