The aggregation of polystyrene-b-poly(ethylene oxide)-b-polystyrene triblock copolymers in aqueous solution

The aggregation of PS4-b-PEO227-b-PS4 triblock copolymer (the PS and PEO are abbreviations of polystyrene and poly(ethylene oxide), and the subscripts represent the degree of polymerization) in aqueous solution was investigated by Nuclear Magnetic Resonance, Fluorescence Probe, and Transmission Electron Microscope techniques. The experimental results showed that the aggregation did occur and the critical concentration for aggregation was about 0.01 g/l. When the concentration of colloid solution was 10 g/l, the spherical aggregate with a highly polydispersity and radii ranging from 100 to 500 nm was observed. The possible structures of primary micelles and micellar aggregates were proposed. Additionally, the aggregation of PS43-b-PEO45-b-PS43 and PS18-b-PEO45-b-PS18 block copolymers was primarily concerned. The spherical aggregates with a certain size distribution were observed by Transmission Electron Microscope.