Identical Diffusion Distributions and Co-Cluster Formation Dictate Azeotrope Formation: Microscopic Evidences and Experimental Signatures.

What selects azeotropic pairs and governs the azeotropic conditions (composition and temperature) is an open and intriguing question. A combined simulation and experimental work presented here investigates this by considering ethanol-water mixtures. We find identical distributions of center-of-mass diffusion coefficients for ethanol and water molecules under the azeotropic condition (95.

Interactions and Dynamics in Aqueous Solutions of pH-Responsive Polymers: A Combined Fluorescence and Dielectric Relaxation Study.

Interaction and dynamics of aqueous solutions of pH-responsive smart polymers are investigated via steady-state, time-resolved fluorescence emission spectroscopy with the help of external local reporter coumarin 153 (C153), while MHz to GHz dielectric relaxation spectroscopic (DRS) measurement reports the intrinsic medium relaxation features. A series of pH-responsive random copolymers () comprising of a pH-responsive moiety 2-((leucinyl)oxy)ethyl methacrylate (l-Leu-HEMA) and hydrophobic methyl methacrylate (MMA) are synthesized and characterized. A balance between the pH-responsive (l-Leu-HEMA) and the hydrophobic (MMA) content dictates the phase transition pH, which is found to be ∼5-7 for these aqueous copolymer solutions (1 mg/mL).

Cloud Point Driven Dynamics in Aqueous Solutions of Thermoresponsive Copolymers: Are They Akin to Criticality Driven Solution Dynamics?

Cloud point driven interaction and relaxation dynamics of aqueous solutions of amphiphilic thermoresponsive copolymers were explored through picosecond resolved and steady state fluorescence measurements employing hydrophilic (coumarin 343, C343) and hydrophobic (coumarin 153, C153) solute probes of comparable sizes. These thermoresponsive random copolymers, with tunable cloud point temperatures ('s) between 298 and 323 K, were rationally designed first and then synthesized via reversible addition-fragmentation chain transfer (RAFT) copolymerization of methyl methacrylate (MMA) and poly(ethylene glycol) monomethyl ether methacrylate (PEGMA). Subsequently, copolymers were characterized by NMR spectroscopy and size exclusion chromatography (SEC).

Dynamics at the non-ionic micelle/water interface: Impact of linkage substitution.

The impact of atom substitution on the glycoside linkage bridging the head and the tail parts in a nonionic surfactant molecule on aqueous dynamics of the resultant micellar solutions has been explored, employing time-resolved fluorescence and dielectric relaxation (DR) measurements. We have utilized n-octyl-β-D-glucopyranoside (OG) and n-octyl-β-D-thioglucopyranoside (OTG) as nonionic surfactants where the oxygen atom in the glucopyranoside unit is substituted by a sulfur atom. The substitution impact is immediately reflected in the dynamic light scattering measurements of aqueous solutions where the estimated size of the OTG micelles is found to be approximately four times larger than the OG micelles.