Star-Like Structure of Oligocarbonate-Fluorene End-Functionalized Poly(ethylene glycol) ABA Triblock Copolymers below the Gel Point

Abstract

ABA-type oligocarbonate-fluorene end-functionalized poly(ethylene glycol) s form micelles with star-like correlations in dilute solutions where water solvates the middle (B) poly(ethylene oxide) block. Using small-angle neutron scattering (SANS), the star-arm aggregation number and arm radius of gyration were characterized by Benoit's star-polymer form factor under θ-solvent conditions and by Alessandrini and Cargnano's renormalization group theory in good solvent. Model-independent SANS Zimm plots provide the radius of gyration, micelle aggregation number, and second virial coefficient (A2) as a function of temperature. In comparison to unfunctionalized poly(ethylene glycol) A2 is consistent with predictions for self-assembling polymers below the gelation point with a theta temperature of ≈ 75 °C.