Synthesis of Amphiphilic Heteroeight-Shaped Polymer <i>Cyclic</i>-[Poly(ethylene oxide)-<i>b</i>-polystyrene]₂ via “Click” Chemistry

Abstract

An amphiphilic heteroeight-shaped polymer cyclic-[poly(ethylene oxide)-b-polystyrene]2 ([c-(PEO-b-PS)]2) composed of hydrophilic PEO and hydrophobic PS blocks was synthesized by combination of “click” chemistry with anionic ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP) mechanisms. According to “core-first” strategy, the A2B2 star-shaped precursor (PEO-alkyne)2-(PS-N3)2 was obtained by successive ROP of EO monomer, ATRP of St monomer, and modification of functional groups. Under high dilution condition, the intramolecular cyclization of (PEO-alkyne)2-(PS-N3)2 by “click” chemistry produced the amphiphilic heteroeight-shaped polymer [c-(PEO-b-PS)]2. The target copolymers and intermediates were well characterized by GPC, MALDI-TOF MS, 1H NMR, and FT-IR. The self-assembly behavior of [c-(PEO-b-PS)]2 and its precursor of (PEO-alkyne)2-(PS-N3)2 were investigated and compared by transmission electron microscopy (TEM) and dynamic light scattering (DLS). In both cases, the spherical micelles were observed, however, the size of formed micelles increased from a star-shaped to a cyclic topology.