Amphiphilic Poly(ethylene oxide)-<i>block</i>-poly(butadiene-<i>graft</i>-liquid crystal) Copolymers: Synthesis and Self-Assembly in Water

Abstract

What could be the self-assembly behavior in aqueous solution for an amphiphilic block copolymer with a very flexible hydrophobic backbone possessing however a liquid crystalline (LC) order? To answer this question, five amphiphilic block copolymers were prepared by grafting, via a thiol−ene addition reaction, four different thiol-functionalized LC mesogens or LC-like side groups on two commercially available poly(ethylene oxide)-<i>block</i>-poly(butadiene) (PEO-<i>b</i>-PB) polymers. These copolymers form monodisperse nanospheres in dilute deionized water with the aid of 1,4-dioxane as cosolvent (dioxane−H₂O system), while in the THF−H₂O system, some give heterogeneous polydisperse micelles and others form large hollow concentric spherical vesicles (“Russian dolls” arrangement). Smectic stripes inside the vesicles and the nanospheres are clearly visualized by cryo-TEM technique.