Supramolecular structures of an amphiphilic hairy-rod conjugated copolymer bearing poly(ethylene oxide) side chain

The structures of an amphiphilic conjugated graft copolymer, poly(2,3-diphenyl-5-(trimethylene-heptadeca(oxyethylene)-methoxy-phenylene vinylene) (denoted as PVEO17) composing of a conjugated DP-PPV backbone and PEO side chains, in bulk and solutions with tetrahydrofuran (THF) and water have been investigated by small-angle X-ray scattering (SAXS). In bulk state, the DP-PPV main chains in PVEO17 stacked to form flat disk microdomains dispersed in the PEO side-chain matrix. The corresponding wide angle X-ray scattering pattern revealed the existence of crystallinity of the PEO side chains. The structure of the polymer in solution was affected by the solvent quality and the polymer concentration. PVEO17 chains were relatively well dispersed in THF. In aqueous solutions, however, the amphiphilic PVEO17 chains aggregated significantly over the concentration range of 1-8 wt%, where the polymer was found to self-organize to form cylindrical micelles with the aggregation number increasing with the increase of concentration. The photophysical properties characterized by UV-Vis and photoluminescence spectroscopy were strongly affected by the aggregation state of the polymer.