Effect of Structure of Graft on the Properties of Graft Copolymers of Acrylamide and Surfactant Macromonomers Dilute Aqueous Solutions
Several surfactant macromonomers (SMMxyz) were prepared by using triblock polymers of ethylene oxide (EO) and propylene oxide (PO) (POx–EOy–POz triblock polymer, x: y: z represent the weight ratio of the different blocks). Then graft copolymers of acrylamide and SMMxyz (PAM-g-SMMxyz) were synthesized. The effects of EO/PO mole ratio, length of grafted SMMxyz and the three relative block sizes on the surface activity and thermo-associativity of PAM-g-SMMxyz dilute solutions were studied. The results showed that the surface tension decreased with increasing PO in the graft at 30°C and decreased with the length of the graft when the temperature was higher than the cloud points of the grafted POx–EOy–POz chains, regardless of EO/PO ratio. When the EO/PO ratio was the same in the SMMxyz, the PAM-g-SMMxyz with higher PO content at the graft end had higher surface activity. With increasing temperature, the hydrodynamic radius (Rh) of PAM-g-SMMxyz in dilute aqueous solution increased. The polymer with shorter grafts may have much more intermolecular interaction points and there were more polymer chains in the polymeric aggregates, which led to Rh increasing with decreasing length of graft. In addition, when the EO/PO was not more than 1:1.74, the three relative block sizes had no great influence on the temperature-associativity of PAM-g-SMMxyz. However, for PAM-g-SMM217 and PAM-g-SMM712, the Rh of PAM-g-SMM217 was smaller than PAM-g- SMM712.
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