The change in excited-state proton transfer kinetics of 1-naphthol in micelles upon the binding of polymers: The influence of hyaluronan hydration

The fast deprotonation of 1-naphthol was studied in aqueous solution and in polymer-cetyltrimethylammonium bromide (CTAB) mixtures using picosecond fluorescence spectroscopy to study the influence of hyaluronan hydration in polymer-surfactant interactions. The aqueous micelle solution showed the expected change of proton transfer rate around the reported critical micelle concentration (∼1 mM). The proton transfer rate dependence on CTAB concentration in the hyaluronan-CTAB and polystyrenesulfonate-CTAB systems differed significantly from that in the aqueous micelle solution. The dynamic study of excited state proton transfer (ESPT) revealed the significant influence of hyaluronan hydration in CTAB micelles. When hyaluronan-CTAB aggregates were formed at the CTAB concentration of 0.5 mM, a tenfold decrease in the rate of deprotonation was observed when compared to polystyrenesulfonate-CTAB aggregates due to hyaluronan hydration. In 2 mM CTAB-hyaluronan aggregates, the rate of deprotonation was found to be almost two times faster than in the 2 mM CTAB or polystyrenesulfonate-CTAB system. Furthermore, the study of excited-state proton transfer of 1-naphthol confirmed that hyaluronan hydration layer penetrates into the micelle and changes the emission characteristics of 1-naphthol.