Hydrophobically associating water-soluble polymers: A dramatic growth of solution viscosity and the specificity of physical gel formation

The rheological properties of dilute and semidilute solutions (viscosity) a nd physical gels (elasticity modulus) of hydrophobically modified self-asso ciated binary polymers (formed by micellar polymerization of acrylamide and methyl methacrylate with side hydrophobic groups (HG) containing 9, 12 and 18 C-atoms), and terpolymers (the same monomers and a charged component so dium acrylate) are studied. The dependences of properties on the length, fo rm (linear or branched) and the number of HG and charges is established. It is shown that a very small number of linear HG leads to a considerably hig her solution viscosity, starting at a smaller concentration compared with t he effects of a larger number of branched HG. Solutions of terpolymers of c oncentration 2-3 wt. % form physical gels that are thixotropic. After dilut ion, the polymers suddenly form gels at certain concentrations without the preliminary stage of viscosity growth.