Aggregation properties of amphiphilic poly(ethylene oxide)‐poly(propylene oxide)‐poly(ethylene oxide) block copolymer studied by cyclic voltammetry

Abstract

The cyclic voltammetric behaviors at a platinum electrode of an amphiphilic block copolymer [poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (F127)] in aqueous solutions were investigated. The mechanism of the electrochemical reaction of F127 at a platinum electrode was deduced. The diffusion coefficients of different-shaped aggregates formed by F127 were determined on this basis. The first and second critical micelle concentrations, corresponding to the formation of spherical micelles and the transition of the spherical to rod-like micelles, were 3.72 × 10 −4 mol·L −1 and 1.49 × 10 −3 mol·L −1 , respectively, which could be confirmed by the fluorescent anisotropy of pyrene in the F127 aggregates and the morphology of F127 micelles observed by freeze-fracture transmission electron microscopy.

Effect of ethanol on the gelation of aqueous solutions of Pluronic F127

“…(1) values of r h,app are inversely proportional to D app , and plots of 1/r h,app against F127 concentration for solutions of 0.5-5 wt.% F127 in 10 and 20 wt.% ethanol/water were linearly dependent on concentration (see Supplementary material), consistent with inherent values of r h of 15.9 nm (10 wt.% ethanol/water, 50°C) and 22.1 (20 wt.% ethanol/water, 50°C) compared with a value 13.5 nm obtained previously for F127 in water at 50°C [18]. Results for solutions in 30 wt.% ethanol/water could not be treated in this way.…”

“…A similar increase in particle size with increase in alcohol concentration has been observed by Bharatiya et al for copolymer P123 in aqueous solutions of various alkanols, and has been ascribed to solvation of the alcohols by the micelles [17]. Swelling of the cores of the micelles of related copolymers is known to lead to formation of elongated (wormlike) micelles [12] and, given recent evidence of the formation of such micelles in dilute solutions of F127 in water [18], this may be so in the present case.…”

Fabrication of PbS microstructures with different shapes in aqueous solutions of amphiphilic triblock copolymer

“…Moreover, the minimum F127 concentration required for the formation of hollow PbS spheres is larger than the critical micelle concentration of F127 (CMC, 3.14 Â 10 À4 mol/L [30]), indicating that the formation of the hollow spheres is related with the interface structures of block copolymer micelles, such as the degree of compactness, the interface rigidity and the curve diameter. On the other hand, the minimum F127 concentration required for the formation of branch-like PbS structures is also larger than CMC, and the compactness degree of the branch-like structures increases with increasing F127 concentration, indicating that the coiling degree of monomeric F127 chain play an important role in the formation of branch-like structures.…”

“…Amphiphilic EOPOEO type triblock copolymers (where EO and PO are polyethylene oxide, and polypropylene oxide, respectively), can form various selfassemblies under certain conditions, such as micelles in aqueous solutions, with the hydrophobic PO block forming a micellar core and the hydrophilic EO block forming a micellar corona or shell around the core [30,31]. Recently, Qi and co-workers have successfully synthesized hollow ZnS and CdS spheres in aqueous solutions of the amphiphilic triblock copolymer P123 (EO 20 PO 70 EO 20 ) at room temperature.…”

Experimental research and DPD simulation on the interaction between an ethoxy-modified trisiloxane and F127

“…Because of broad molecular weight distribution, unimer or oligomer forms at the concentration below CMC [36,37]. The CMC of F127 should be determined by the second break, which is 1.70 × 10 4 mg L −1 comparable to the value reported [38]. The addition of F127 to Ag-64 solutions also leads to two breaks (T 1 and T 2 ) in the surface tension isotherms, and it can be predicted that the F127/Ag-64 complex is formed according to Flomer's work [39].…”