Dynamics of Micro- and Macrophase Separation of Amphiphilic Block-Copolymers in Aqueous Solution

Abstract

The dynamics of purified poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO−PPO−PEO) block-copolymer micellization and phase separation in aqueous solutions were studied using the iodine laser temperature-jump and stopped flow techniques. The changes in the micellar solutions were followed by either light scattering or fluorescence of 1,6-diphenyl-1,3,5-hexatriene (DPH), which is a probe located in the micelle interior. Three different relaxation processes were observed for the temperature range covering the micro- and macrophase separation of the EO13PO30EO13 (Pluronic L64) block-copolymer. The fastest process corresponds to the incorporation of unimers into micelles which leads to larger micelles that are not thermodynamically stable. This process is followed by a relaxation with negative amplitude during which the micellar core is dehydrated and a redistribution of micellar sizes is achieved. The third relaxation process corresponds to the clustering of micelles into larger aggregates which is associated with the initial step of macrophase separation. Other PEO−PPO−PEO block-copolymers, like EO19PO43EO19 (Pluronic P84) and EO27PO61EO27 (Pluronic P104), were investigated to provide additional information concerning the second relaxation process. Mixed micelles containing sodium dodecyl sulfate were studied to support the assignment of relaxation processes involving micellar collisions. This study of the dynamics of purified PEO−PPO−PEO block-copolymers clarifies several controversial points because the dynamics were investigated over a wide temperature and concentration range and avoid impurity effects.

Comparison of aggregation behaviors between branched and linear block polyethers: MesoDyn simulation study

“…At the end of simulation, the small micelles and huge micellar clusters coexist. The micellar clusters are also found for other systems in the experiment [64,65] and simulation [66].…”

Synthesis of Double‐Hydrophilic BAB Triblock Copolymers via RAFT Polymerisation and their Thermoresponsive Self‐Assembly in Water

“…The self-assembly of such symmetrical amphiphilic triblock copolymers depends sensitively on the sequence of the blocks. [30][31][32] With A representing the hydrophilic block and B the hydrophobic block, ABA block copolymers tend to form core-shell micelles in aqueous solution, [33] while copolymers with a BAB architecture tend to give more complex structures, such as flower-like or interconnected micelles and networks, [34][35][36] which have also been discussed from a theoretical point of view. [37][38][39] Network formation is an important feature which distinguishes BAB block copolymers from self-associated AB diblock chains.…”

Effects of ageing conditions and block copolymer concentration on the stability and micellization of P123-Ti4+ sols prepared by the templating method

“…For the samples aged at 55, 60, and 65°C for 30 min, the peak appearing at lower relaxation time is possibly that of unimers/unimer clusters and that appearing above *100 l S is possibly attributed to micelles and micellar clusters/aggregates. The latter could also have been affected by the exchange of unimers with micelles [44]. Further, increasing the ageing temperature above 50°C gave rise to a slight shift of the position of this peak in the relaxation graph to longer periods, suggesting increased aggregation/clustering (Fig.…”

“…The changes in the micellar sizes with temperature show that the micelles are dynamic aggregates in which the individual polymer chains constantly move from one micelle to another. It has already been shown that below *15°C water is a good solvent for PPO, whereas PPO aggregates at high temperatures [44]. On the other hand PEO is dominantly hydrophilic within the temperature range 0 to 100°C.…”