Morphological transition of triblock copolymer cylindrical micelles responding to solvent change

Reported is the morphological transition of micelles of a BCA triblock copolymer after the solvation medium was changed from one that was selective for B and A to one that was selective for A only. Here B, C, and A denote poly(tert-butyl acrylate), poly(2-cinnamoyloxyethyl methacrylate), and the amine-bearing poly(N,N-dimethylaminoethyl methacrylate) blocks respectively. In methanol, BCA formed cylindrical micelles with the insoluble C block as the core and the soluble A and B blocks as the corona. Adding water reduced the solubility of the B coronal chains. The micellar morphological evolution was followed using transmission electron microscopy (TEM) by analyzing samples, which were taken at different times after water addition to the water volume fractions (f _w) of 2.7% and 10.7%, respectively. Also reported are the stabilized morphologies of the micelles formed in methanol/water mixtures with f _w ranging from 2.9% to 23%.