Cavitation Enables Switchable and Rapid Block Polymer Exchange under High- χ N Conditions

Kinetically trapped micelles are a novel platform for diverse emerging applications. However, their homogenization and reproducibility is inherently challenging due to the high- χN barrier toward chain exchange processes. Sonication enables switchable micelle exchange where cavitation leads to exchange and cessation returns micelles to kinetic entrapment. The mechanism was posited to be an agitation induced exchange process similar to recent developments with vortexing. This study reports the first SANS measurements of chain exchange during cavitation induced exchange (CIE). The mixed chain concentration progresses linearly with sonication time, analogous to vortexing. In contrast, the rate of CIE was directly proportional to the polymer concentration. This feature indicates that CIE uniquely overcomes the energetic barriers that reduce exchange rates with other methods. Furthermore, the linear progression with time and direct concentration dependence suggest that exchange is limited by the rate of micelle-bubble interactions. CIE thus supports switchable entrapment with rapid exchange rates, supporting ongoing developments with kinetically controlled micelles.