Block Copolymer Micelles with an Intermediate Star-/Flower-Like Structure Studied by 1H NMR Relaxometry

H-1 NMR relaxation is used to study the self-assembly of a double thermoresponsive diblock copolymer in dilute aqueous solution. Above the first transition temperature, at which aggregation into micellar structures is observed, the trimethylsilyl (TMS)-labeled end group attached to the shell-forming block shows a biphasic T-2 relaxation. The slow contribution reflects the TMS groups located at the periphery of the hydrophilic shell, in agreement with a star-like micelle. The fast T-2 contribution corresponds to the TMS groups, which fold back toward the hydrophobic core, reflecting a flower-like micelle. These results confirm the formation of block copolymer micelles of an intermediate nature (i.e., of partial flower-like and star-like character), in which a part of the TMS end groups folds back to the core due to hydrophobic interactions. <boxed-text content-type="graphic" position="anchor"> <graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="urn:x-wiley:10221352:media:macp201300753:macp201300753-abs-0001">image</graphic