Micellization Dynamics and Impurity Solubilization of the Block-Copolymer L64 in an Aqueous Solution

Abstract

The dynamics of the micellization of Pluronic® L64 (EO13PO30EO13, PEO/PPO = 2/3) was studied by employing the iodine laser temperature-jump technique. These studies show a more complex behavior than previously described. Three relaxation processes were observed, depending on the temperature at which experiments were performed. The first two of these relaxation processes are related to the unimer incorporation into micelles and the redistribution of micelles after incorporation of the unimers. The third relaxation process, which had not been previously observed, occurs at high temperatures and is related to the clustering of micelles into larger aggregates. In addition, the presence of impurities and hydrophobic components was shown for the first time to significantly affect the dynamics of L64 micellization.

Conductivity of water-in-oil microemulsions stabilized by mixed surfactants

“…Both experiments show that low-molar-mass impurities (oligomers of repeating units 3) were, in L-64 and L-62, while no such contaminants were found in L-44, L-43, or 10R5. Such impurities could have a great effect on the system phase behavior [42]; hence both L-64 and L-62 were purified as follows: the polymer was first dissolved in plenty of THF (Aldrich, 99.9% anhydrous), and then the solution was titrated with twice-distilled hexane (Sigma, 99 + %) until the polymer precipitated. The above procedure was repeated three times, and then the precipitate was centrifuged and the polymer dried in a vacuum oven at 50 • C overnight.…”

Solubilization of Hydrophilic Compounds in Copolymer Aggregates

“…The large discrepancy among the reported cac values can be attributed to a broad unimerto-micelle transition, technical problems, and heterogeneity of commercial polymers. In particular it has been shown that impurities strongly affect L64 micellization (30). As a result, it is difficult to ascertain the presence of block copolymer micelles under the present experimental conditions for L64.…”

Self-assembly of multi-responsive poly(N-isopropylacrylamide)-b-poly(N,N-dimethylaminopropylacrylamide) in aqueous media

“…For Pluronic Ò surfactants, at lower temperature polymer remains as unimolecularly dissolved but at higher temperature more hydrophobic component present becomes insoluble causing turbidity in solution. At higher temperatures when micelles form, the minor insoluble component gets solubilized leading to transparent solution well below the CPT [49]. The formation of micelles, intermicellar particles, compactness and further disintegration of clusters shows similar turbidity-temperature behavior [47,48].…”