Solvation Dynamics in the Water Pool of Aerosol Sodium Dioctylsulfosuccinate Microemulsion:  Effect of Polymer

Abstract

Solvation dynamics of 2,6-p-toluidinonaphthalene sulfonate (TNS) is studied in a large water pool (w 0 = 56) of aerosol sodium dioctylsulfosuccinate (AOT) microemulsion in n-heptane in the absence and the presence of a hydrophilic polymer, poly(vinylpyrrolidone) (PVP). The solvation dynamics of TNS in AOT microemulsions without polymer is found to be biexponential with a major component of 300 ± 30 ps (75%) and a slow component of 500 ± 50 ps (25%) with an average solvation time of 350 ps. In the presence of a polymer (0.75 wt % PVP) in the water pool, the solvation dynamics of TNS is found to be faster with components 70 ± 10 ps (75%) and 250 ± 25 ps (25%) and having an average solvation time of 115 ps. The very fast solvation dynamics in the presence of 0.75 wt % PVP in the water pool is similar to that in bulk water and is ascribed to strong binding of TNS to PVP. When the concentration of the polymer is increased to 2.5 wt % PVP, the solvation dynamics of TNS in polymer encapsulated microemulsions is found to be markedly slower. In the presence of 2.5 wt % PVP, the solvation dynamics in the water pool exhibits components of 100 ± 10 ps (33%), 600 ± 50 ps (47%) and 11 ± 1 ns (20%), with an average solvation time 2500 ps. This clearly indicates that, at high concentration of the polymer, dynamics of the water molecules inside the water pool of microemulsion is severely constrained.

Validation and Divergence of the Activation Energy Barrier Crossing Transition at the AOT/Lecithin Reverse Micellar Interface

“…The total estimated Stokes' shift is thus 2540 cm -1 compared to the observed Stokes' shift of 1690 cm -1 . Thus, in our picosecond setup, we have missed 33% of the total dynamic spectral shift, which closely matches with that obtained by Sen et al 51 Figure 5a displays the Arrhenius plot of ANS in RM in the temperature range of 293-343 K. Assuming Arrhenius dependence of the rate constant (1/〈τ solv 〉), the activation energy (E a ) has been evaluated from the logarithmic plot of 1/〈τ solv 〉 against 1/T. For ANS, the first three temperatures (293-328 K) follow regular Arrhenius type behavior, whereas a strong deviation is found around 343 K (Figure 5a).…”

Hydrogen‐Bonded Large Molecular Aggregates of Charged Amphiphiles and Unusual Rheology: Photochemistry and Photophysics of Hydroxyaromatic Dopants

“…For long-chain alkyl-substituted 2-naphthols, the ESPT rate constants are shown to decrease and the pK a to increase in CTAB micellar solutions in comparison with 2-naphthol, although they are almost the same in homogeneous solution [98]. Similar effects of alkyl substitutions were also observed for pK a in the ground state.…”

Solvation dynamics in DMPC vesicle in the presence of a protein

“…The dramatic retardation of solvation dynamics in a confined environment markedly slows down many polar reactions [2]. The slow component of solvation has been detected in many systems, e.g., protein [3][4][5][6][7], lipid vesicles [8,9], reverse micelles [10], DNA double helix [11] and in hydrophilic polymers [12,13]. Several theoretical models and computer simulations have been used to explain the slow solvation dynamics in confined environments.…”