In situ monitoring of block copolymer self-assembly through con-trolled dialysis with light and neutron scattering detection

Solution self-assembly of amphiphilic block copolymers (BCs) is typically performed by solvent to water exchange. However, BC assemblies are often trapped in metastable states depending on the mixing conditions, such as the magni-tude and rate of water addition. BC self-assembly can be performed under near thermodynamic control by dialysis which accounts for a slow and gradual water addition. In this communication we report the use of a dialysis cell specif-ically designed to continuously monitor by dynamic light scattering and small-angle neutron scattering the morpho-logical changes of PDMS-b-PEG BCs during THF to water exchange. The complete phase diagrams of equilibrium structures can then be established. Spherical micelles first form before evolving to rod-like micelles and vesicles, de-creasing the total interfacial area of aggregates in response to increasing interfacial energy. The dialysis kinetics can be adapted to the time scale of self-assembly by modifying the membrane pore size. The approach described herein should be relevant in polymer self-assembly and in supramolecular chemistry in general to better understand the interplay between thermodynamics and kinetics in aggregate formation.