Anionic synthesis and characterization of poly(styrene‐block‐ethylene oxide) polymers with fluorescent probes at the block junctions

Abstract

AbstractFluorescent‐labeling reactions of poly(styryl)lithium were effected with either 2‐(1‐phenylethenyl)naphthalene or 1‐phenyl‐1‐(1‐pyrenyl)ethylene followed by functionalization of the resulting 1‐phenyl‐1‐arylalkyllithium species with ethylene oxide. The resulting polymeric alkoxylithiums were used to initiate the anionic polymerization of ethylene oxide in a mixture of benzene and dimethyl sulfoxide. A series of block copolymers [Mn(PS)=5.1 × 103 g/mol); Mw/Mn=1.02] with 20–40wt% ethylene oxide were characterized by thin‐layer chromatography, size exclusion chromatography, 1H NMR and quantitative UV‐visible spectroscopy. Fluorescence measurements on the block copolymers were carried out in 1,2‐dichloroethane with varying amounts of methanol. No excimer formation was detected for either naphthalene‐ or pyrene‐labeled block copolymers. Energy transfer from the naphthalene‐ to the pyrene‐labeled polymers was observed at about 80 vol.% methanol. These results are discussed in relationship to the interfacial boundary distances in the block copolymer micelles as deduced by application of the “Spectroscopic Ruler”.