Rheology of an aqueous solution of an end-capped poly(ethylene glycol) polymer at high concentration

Generally it is observed that the viscosity of an aqueous solution of a hydrophobically modified polymer increases with concentration; however, here it is shown that the viscosity profile of an end-capped poly(ethylene glycol) polymer passes through a maximum. Thus, a substantial decrease in viscosity is observed at high concentrations (greater than or equal to 50 wt%). The observation is suggested to be due to a gradual change, on the molecular level, from a structure containing micellelike structures that are interconnected via polymer bridges to a more meltlike state, where micro segregation in hydrophilic and hydrophobic regions is less pronounced.