Polybutadiene Elastomers with Degradation Profiles Programmed by Microencapsulation and Controlled Release of Metathesis Catalysts

The principles of microencapsulation and controlled, <i>in situ</i> release of functional compounds have been exploited extensively in the development of stimuli-responsive materials, such as self-healing composites and coatings with sensing capabilities. In contrast, there are comparatively few examples by which the same principles have been utilized for stimuli-responsive polymer degradation, despite recent evidence that <i>in situ</i> transformations may present new and improved opportunities for remediation of plastic waste. With this context in mind, we illustrate that microencapsulation of alkene metathesis catalysts provides a powerful method to create polybutadiene (PB) elastomers with programmable degradation profiles. Such catalysts, highly active towards depolymerization of PB via ring-closing metathesis, are rendered effectively latent by microencapsulation within a glassy polymer. The micron-sized polymer/catalyst particles are easily compounded into PB resin which is subsequently crosslinked by radical chemistry, yielding particle-loaded elastomers with similar mechanical properties to particle-free controls. Relying on judicious selection and design of the encapsulant or encapsulating system, the catalyst can be released <i>in situ</i> through temperature, time, or light exposure, among other phenomena, thereby initiating rapid depolymerization of the elastomer to soluble products. We anticipate that this approach can be expanded to deliver existing and emerging functional compounds for chemical transformation of polymers with reduced resource requirements, as well as precise control over the conditions under which such transformations are effected.