Tuning the Length of Filomicelles Prepared Via Templated Polymerization‐Induced Self‐Assembly

High-aspect-ratio polymeric micelles (filomicelles, FMs) are attractive anisotropic nanoparticles for a wide range of applications, however, their formation is typically confined to narrow hydrophilic/hydrophobic polymer block ratios, limiting systematic structure-property investigations. Consequently, independent control over micelle width, length, and stiffness remains challenging. A supramolecular polymerization-induced self-assembly (PISA) strategy using a bis-urea core template was recently shown to robustly yield wormlike micelles across a wide range of core block lengths; however, the resulting FM lengths remained highly polydisperse. Herein, we investigate two strategies to tune the contour length: (i) Blending in polymer without the bis-urea sticker and (ii) post-micellization sonication. Unexpectedly, incorporating non-sticker polymer can increase the contour length. Transmission electron microscopy (TEM), fluorescence cross-correlation spectroscopy (FCCS), and high-resolution atomic force microscopy (AFM) were used to elucidate the key factors contributing to this peculiar self-assembly mechanism. Sonication-induced cleavage led to shortening of the particles and narrower polydispersity in length. Combined, the two strategies provide access to a wide range of anisotropic micelles with accessible aspect ratios ranging from 1 to >150. Considering their long-term (colloidal) stability, the presented system is an ideal model to study the effect of micellar anisotropy, for example, in drug delivery relevant scenarios.