Macromolecules, Vol.41, No.15, 5854-5862, 2008
Asymmetric end-capped poly(ethylene oxide). Synthesis and rheological behavior in aqueous solution
A method was developed to prepare asymmetric end-capped poly(ethylene oxide)s (PEOs), containing an alkyl group on one chain end and a perfluoroalkyl group on the other one (C18H37-PEO-C2H4-C8F17 and C18H37-PEO-C10H20-C8F17). These new telechelic associative polymers (APs) were synthesized by anionic polymerization of ethylene oxide initiated by an alkoxide (C18H37-O-K+) followed by esterification. The theological behavior of asymmetric and analogous symmetric APs in aqueous solutions has been investigated as a function of polymer concentration (C), hydrophobic end-cap and surfactant used to homogenize the system: sodium dodecyl sulfate (SDS) or lithium perfluorooctyl sulfonate (LiFOS). A steep increase of the static viscosity eta, attributed to the formation of a multiconnected network, is observed for C approximate to 1 wt %. Semidilute solutions present a Maxwellian theological behavior with only one relaxation time tau associated with the least hydrophobic end group. The viscoelastic response is modified by the interactions between hydrophobic end groups and surfactant inside mixed aggregates.