Effect of urea on biomimetic aggregates

The effect of urea on biomimetic aggregates (aqueous and reversed micelles, vesicles and monolayers) was investigated to obtain insights into the effect of the denaturant on structured macromolecules. Direct evidence obtained from light scattering (static and dynamic), monolayer maximum isothermal compression and ionic conductivity measurements, together with indirect evidence from fluorescence photodissociation, fluorescence suppression, and thermal reactions, strongly indicates the direct interaction mechanism of urea with the aggregates. Preferential solvation of the surfactant headgroups by urea results in an increase in the monomer dissociation degree (when applied), which leads to an increase in the area per headgroup and also in the loss of counterion affinitie

Characterization of PMMA-b-PDMAEMA aggregates in aqueous solutions

International audienceDiblock amphiphilic copolymers form aggregates in some solvents. Such aggregates exhibit different morphologies, depending mainly on the polar/apolar block ratios. Aggregation of copolymers with polar block excess leads to micelle-like aggregates, known as polymeric micelles, which can be used as vehicles for drug and gene delivery, water decontamination, and catalysis. Here, we synthesized by RAFT polymerization three different polymers namely [dimethyl 2-(aminoethyl) methacrylate] (PDMAEMA), poly (methyl methacrylate) (PMMA) copolymers, and PDMAEMA-block-PMMA and characterized their aggregates by NMR spectroscopy and pH titrations. We investigated correlations between their chemical structure, aggregation behavior, protonation degree, and chain conformation in the corona. Decreased amine protonation in the copolymers reduced the electrostatic repulsion, and the apparent pKa of the amino groups approached that of isolated amine. These effects increased compactness and sizes of the polymers and their aggregates at higher pH as reflected by the increased NMR line widths

Risky arbitrage, asset prices, and externalities

C62, D50, Risky arbitrage, Competitive equilibrium, Viable asset prices,