Kinetically trapped micelles are a novel platform for diverse emerging applications from drug delivery, to nanoreactors, and templates for porous nanomaterials. Kinetic control allows micelle size to be decoupled from any subsequent application. However, micelle homogenization and size tuning are inherently challenging due to the high-χN barrier toward chain exchange processes. It was recently discovered that sonication enables switchable exchange where cavitation leads to chain exchange and cessation returns micelles to kinetic entrapment. SANS measurements were used to quantify chain exchange during cavitation induced exchange (CIE). The extent of exchange increases linearly with CIE time and the rate of chain exchange was directly proportional to the polymer concentration. A CIE mechanism is posited that is consistent with these observations and the atypical concentration dependence. The absence of chain exchange is particularly useful when micelles are used as templates. Persistent Micelle Templates (PMT) were recently developed to enable independent control over pore and wall dimensions. PMT relies upon kinetic controlled micelles of constant size where chain exchange is suppressed with solution water content. Typical PMT embodiments involve water-reactive precursors that unfortunately lower the barrier to exchange upon precursor addition. A new approach was developed to overcome this limitation using <i>ex situ</i> hydrolysis. This approach significantly decouples micelle kinetic control from nanoparticle chemistry and expands the range of precursor additions while maintaining PMT control. These works support the size tuning and homogenization of kinetic controlled micelles via CIE and develop subsequent processing chemistries to support robust deployment of these micelles as templates.

Kinetic control of block polymer micelles: Cavitation induced exchange and templates for nanomaterials

2019 Spring National Meeting

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