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

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 A 2 B 2 star-shaped precursor (PEO-alkyne) 2 -(PS-N 3 ) 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-N 3 ) 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, 1 H NMR, and FT-IR. The self-assembly behavior of [ c -(PEO- b -PS)] 2 and its precursor of (PEO-alkyne) 2 -(PS-N 3 ) 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.