Competitive interactions between PEO-PPO-PEO block copolymer and PEO at silica
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PEO-PPO-PEO block copolymers are surface active triblock copolymers. They are widely used in many industrial applications, such as mineral separation, detergency, drug delivery and oil recovery. Further exploration of the adsorption of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)—type triblock copolymers was taken by our group. In our study, the effect of PEO with low molecular weight on the adsorption of PEO-PPO-PEO triblock copolymer (Pluronic P105: EO 37 -PO 56 -EO 37 ) at silica was investigated using a dye-solubilization technique and capillary viscometry. PEO had an effect on the organization of Pluronic P105 in silica nanoparticle dispersions. Pyrene fluorescence experiments revealed that the critical surface micelle concentration (csmc) increased with increasing concentration of the additives. The cdc values in 0.01wt% nanoparticle dispersions were ∼0.07wt% and ∼0.05wt% for PEO 200 and PEO 600, respectively. In 0.1wt% nanoparticle concentration, the cdc values were ∼0.1wt% and ∼0.07wt% for PEO 200 and PEO 600, respectively. The capillary experiments revealed that the adsorbed layer thickness decreased from 15.7 nm to 12 nm and 10 nm for PEO 200 and PEO 600, respectively with increasing concentration of PEO. Furthermore, based on the discussion about the relatively high value of the adsorbed layer thickness above the plateau region in capillary experiment, it was predicted that the presence of PEO can cause partial desorption of P105 on the silica surface.