Abstract: The effects of 1-butanol on temperature-dependent micellization of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer(PEO-PPO-PEO) in D₂O were investigated by 1H nuclear magnetic resonance (NMR) spectroscopy. The chemical shift of the methyl groups in the PPO blocks was used to characterize the aggregation process. It was found that addition of 1-butanol reduced the critical micellization temperature (CMT) of PEO-PPO-PEO in aqueous solution. The chemical shift of the methyl protons in 1-butanol was found to increase after mixing with PEO-PPO-PEO, indicating that the alkyl head of 1-butanol must have interacted with the triblock copolymer and entered into the micellar core. The results of selective ROE experiments further demonstrated that, by such interaction, the alkyl head of 1-butanol was inserted into the hydrophobic micellar core while its hydroxyl tail remained at the micellar shell.

Key words: NMR, aggregation, selective ROE, PEO-PPO-PEO, micellization