Recoverable creep compliance properties of associative model polymer and polyoxyethylene solutions

Hydrophobically modified polymers are composed of water soluble and water i nsoluble (hydrophobic alkyl end groups) components. They are referred to as associative polymers since their aqueous solutions exhibit enhanced viscos ities due to the aggregation of their alkyl end groups into micelle-like st ructures. The aggregation is attributed to the rejection of the hydrophobic end groups by the water. The rheological properties including the creep re covery behavior of associative model polymer solutions were determined as a function of molecular weight, solution concentration, shear rate, temperat ure, and solvent type in this investigation. These polymers are composed of a linear water soluble polyoxyethylene backbone chain extended with isopho rone diisocyanate and end capped with hexadecyl groups, and have molecular weights ranging from 1.7x10(4) to 8.4 x 10(4) g/mole. For comparison purpos es, poly(oxyethylene) resins of various molecular weights were also evaluat ed. A previously obscured mechanical terminal dispersion, which diminishes with increasing polymer concentration and decreasing temperature, has been clarified. (C) 2000 The Society of Rheology. [S0148-6055(00)01004-X].