Monomolecular Micelles Based on Amphiphilic Invertible Polymers

Abstract

Using surface tension measurements, solubilization of dimethyl yellow dye and solvatochromic dye E t 30, and fluorescence spectroscopy, amphiphilic polyesters containing alternated hydrophilic poly(ethylene glycol) fragments and lipophilic dicarboxylic acid or polytetrahydrоfuran moieties in the polymer backbone have been shown to form monomolecular micelles in aqueous solutions at the concentrations of 10 -7 -10 -4 %. These monomolecular micelles have been demonstrated to possess invertibility and respond to the change in a medium polarity.

Micellization and Adsolubilization of Amphilic Invertible Polyesters

“…Following fast decrease of surface tension indicates the formation of a monomolecular adsorption layer at the air/water interface and monomolecular micelle aggregation into polymolecular micelles (cac 1 ). Similar behavior has been observed for the amphiphilic invertible polyesters based on the same aliphatic dicarboxylic acid and shorter PEGs (i.e., PEG-300 and PEG-600) that have demonstrated a clear low-concentration break point [59]. Conspicuously, a change in the chemical composition of PEG 1000 D and PEG 1000 S (length of hydrophobic fragment in the macromolecule), and therefore their hydrophiliclipophilic balance, results in a difference in the behavior of the surface tension isotherm at the high concentrations recorded for PEG 1000 D in comparison to PEG 1000 S. The slope on the surface tension vs. concentration plot is well expressed for the more hydrophobic PEG 1000 D and a second break point (second critical aggregation concentration cac 2 ) can be determined for PEG 1000 D. The cac 2 point implies the formation of polymolecular micelles, their adsorption at the interface that is accompanied with the structural rearrangements in the adsorbed layer.…”

Amphiphilic Polymers Containing Cholesterol for Drug Delivery Systems

“…Table 2 shows that the values of CMC k are lower than CMC σ which correspond to the point of break on the surface tension isotherm. CMC k corresponds to the concentration under which the formation of micellar structures starts and CMC σ is determined from isotherms of surface tension (a concentration of adsorbed layer saturation at the water-air interface by Na-CholMA-MA-PEMA and its aggregation process has completed) [54]. Obviously, this saturation will occur at higher concentrations than CMC k ones.…”