Solvation dynamics in aqueous polymer solution and in polymer-surfactant aggregate

Abstract

Solvation dynamics of 2,6-p-toluidinonaphthalene sulfonate (TNS) is studied using picosecond time-resolved emission spectroscopy in an aqueous solution of poly(vinylpyrrolidone) (PVP) and in a polymer-surfactant aggregate consisting of PVP and sodium dodecyl sulfate (SDS). On addition of PVP to an aqueous solution of TNS, the emission quantum yield (φ_f) of TNS increases about 210 times in 0.75 wt % aqueous solution of PVP. The solvation dynamics of TNS in 0.75 wt% aqueous solution of PVP is found to be biexponential with a major component (85%) of 60 ps and a slower one of 800 ps (15%). The retardation of the solvation dynamics in the dilute polymer solution compared to that in the bulk water is attributed to the restricted movement of water molecules in the vicinity of the polymer chains. The solvation dynamics of TNS in the PVP-SDS aggregate is described by two components, 300 ± 20 ps (55%) and 2500 ± 100 ps (45%). The slower solvation dynamics in PVP-SDS aggregate compared to PVP alone or SDS alone indicates serious restrictions on the mobility of the water molecule squeezed between polymer chains and micellar (SDS) surface.