The Effect of MolecularWeight on the Behaviour of Step-growth Hydrophobically Modified Ethoxylated U

Two model thickeners of HEUR polymers were synthesized by step-growth polymerization of poly (ethylene oxide) (PEO) with dicyclohexylmethane diisocyanate (H12MDI). First, the prepolymers were produced with different molecular weights by changing the molar ratios of the initial reactants. Then, S-G HEUR model thickeners were produced via reacting of the prepared isocyanate terminated prepolymers with monofunctional dodecyl alcohol. In this way, two polyurethane based model thickeners were obtained with different molecular weights arising from various hydrophilic lengths. The response of these S-G HEUR thickeners in aqueous solutions to both steady shear and oscillatory shear was determined. Considerable increases in thickening efficiency as decreasing molecular weight of model thickeners were observed. Also dynamic measurements verified the results obtained from the steady shear measurements about the effect of molecular weight on the viscoelastic properties of aqueous S-G HEUR solutions.