Molecular aggregations and supramolecular architectures of amphiphilic PEO17–OPV3 and its hybrid with silica

Abstract

The synthesis, luminescence properties and self-assembly of a specifically-designed amphiphilic PEO₁₇–OPV₃ molecule (and its hybrid with silicates) to form ring-like disks are described. The synthesis was begun with the Wittig–Horner reaction to form a co-planar π-conjugated PPV oligomer segment, followed by linking with PEO₁₇ through a sulfonate group that causes a twist in the molecule between the hydrophobic and hydrophilic segments. Due to its amphiphilic nature, its photoluminescence behavior is greatly affected by the solvent type and concentration. The deposition of PEO₁₇–OPV₃ molecules on mica with a proper co-solvent was able to form a ring-like supramolecular architecture of ca. 30 nm in diameter as observed by atomic force microscopy (AFM). The width of the enclosed peripheral area on both sides of the ring is on the same order of magnitude as the length of the PEO₁₇–OPV₃ molecule. The self-assembly of a PEO₁₇–OPV₃ hybrid with silica to form a ring-like disk of ca. 150 nm diameter and ca. 0.65 nm thickness was also observed. The latter is roughly equal to the width of rod segment, implying that π–π stacking governs the self-assembly process in the co-organization between PEO₁₇–OPV₃ molecules and silicates, whereas the twist in molecules orients the ring formation. As a result, a multi-lamellar phase transformation mechanism is proposed for the formation of such a supramolecular architecture.