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| - Study of Salt Effects on the Micellization ofPEO−PPO−PEO Block Copolymer in Aqueous Solution byFTIR Spectroscopy
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| - The micellization of poly(ethylene oxide)−poly(propylene oxide)−poly(ethylene oxide) (PEO−PPO−PEO) block copolymer in aqueous solution in the absence and presence of salts was studied by Fouriertransform infrared (FTIR) spectroscopy. The temperature-dependent changes of the C−O−C stretchingvibration band were used to denote critical micellization temperatures (CMT). The CMT of Pluronic F127in aqueous solution was modified significantly by the addition of salts as previously shown. The proportionof the anhydrous methyl groups was increased, while the proportion of the hydrated methyl groups wasdecreased during the micellization process. The dehydration of the Pluronic F127 ether backbone in themicellization process could also be inferred by the FTIR spectral data from a shift of the frequency of theC−O−C stretching band toward higher wavenumbers and broadening of the bandwidth of the C−O−Cstretching band. The salt influence on the bandwidth is stronger than that on the wavenumber for theC−O−C stretching vibration. The microenvironmental difference between the PPO and PEO blocks of thecopolymer is smaller in aqueous KBr solution than in other types of salt solutions. It was also found thatpart of the PEO segments of Pluronic F127 in aqueous salt solutions are in the crystalline state.
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