(a) Cryogenic transmission electron microscopy (cryo-TEM) images showing changes in micelle core radii (Rc) over 21 days post-dialysis. The polymer concentration was initially 10 mg ml−1, and the THF content was 43% by volume before dialysis. Scale bar, 100 nm. (b) Corresponding histograms of micelle sizes obtained from analysis of cryo-TEM images. The relative percentages of the smaller (Rc <8 nm) and larger (Rc ⩾8 nm) core radii populations are shown on the histograms. Sample sizes for each histogram ranged between 450 and 3,000 micelles.