Dynamic Light Scattering Studies on the Effect of 1‐Alkanols, Alkanediols and Alkoxyethanols on the Micelles of a Moderately Hydrophobic/Hydrophilic PEO‐PPO‐PEO Triblock Copolymer

Abstract

The results on changes in the apparent hydrodynamic diameter (D h ) of micelles in a solution containing 5% of a moderately hydrophobic/hydrophilic triblock PEO-PPO-PEO copolymer in the presence of several hydroxyl compounds at 23°C from dynamic light scattering (DLS) are reported. Distribution plots show micelles with hydrodynamic diameter *17 nm and low polydispersity (\0.1) except at low concentrations where a unimer peak (* 4 nm) was also noticed. These additives increase/ decrease the micelle size and show micellar transition depending upon their hydrophilicity/hydrophobicity. The results are discussed in terms of the effect of the additives on altering water structure and their partitioning in micelle. Short chain alcohols (C 1 -C 3 ) increase solvation of PEO and thus increase micelle hydrodynamic size while higher alcohols, initially reduce D h due shrinkage of PEO followed by micellar growth at higher concentrations. Among ax-alkanediols, C 2 and C 4 diols increase micelle size by immobilizing water sphere around the micelles whereas higher diols form wicket like structures and reside in palisade layer. Isomeric hexanediols (1,2; 1,5; 2,5 and 1,6) alter micelle size in different ways depending on their hydrophobicity. In C 6 EO m (m = 0, 1, 2), as the number of EO group increases, it becomes more hydrophilic and increases D h at higher concentration. Addition of a hydrophobic triblock copolymer leads to unfavorable mixing with a moderately hydrophobic/hydrophilic triblock copolymer which results in increase in size, while the addition of a hydrophilic counterpart increases the average hydrodynamic size and follows appearance of unimer peak.

A peptide-PEG conjugate-directed nanoperiodic hierarchical architecture by spatial selective self-assembly at the solid/water interface

“…1B). When the peptide-PEG conjugates formed random coils, the size roughly corresponded to the unimer configuration of a hydrophilic polymer 34,35 and a protein 36,37 which was analogous to the molecular weight of the peptide-PEG conjugate, composed of 16 amino acid residues and a 70-mer PEG segment. Thus, at pH 12.0, the peptide-PEG which adopted a random coil aggregation state was highly dispersed in a monomeric spherical configuration.…”

Experimental and Computational Study of the Effect of Alcohols on the Solution and Adsorption Properties of a Nonionic Symmetric Triblock Copolymer

“…Interestingly, a recent study by Parekh and Bahadur indicated through dynamic light scattering measurements of a series of PEO–PPO–PEO block copolymers with alkanols (as well as alkoxyethanols and alkanediols) that the hydrodynamic diameter of the micelles changed as a function of the alcohol type. They found that short chain alkanols tend to remain in the aqueous phase but increased the hydrodynamic radius due to the solvation of the PEO shell (similarly to what is depicted in Figure b).…”