Magnetic Triggering of Functional Organosilica Filler Particles for Controlling the Thermoreversible Attachment to Polymer Matrices.

Polymer materials containing filler particles are widely used in automotive components, construction materials, packaging materials, medical devices and supplies, and much more. The fillers strongly modulate the properties of the composite. In some applications, one is interested in smart features of those composites, meaning one can post-synthetically and reversibly change the characteristics as a response to an easy-to-apply trigger. For example, if the excision of an implant material may become necessary, then the polymer-filler hybrid changing from mechanically robust to soft(er) would be very beneficial. Here, we present a proof-of-concept study that shows that stimuli-responsive polymer-filler composites can be achieved by functional organosilica nanoparticles. The nanoparticles comprise a superparamagnetic core surrounded by a mesoporous organosilica shell. The polymer matrix is attached to the filler via Diels-Alder coupling to maleimide groups present at the surface of the organosilica. Exposure to an alternating magnetic field generates local heat in the organosilica particles. Utilizing fluorescence probes bound to the polymer backbone's side chains, we could prove that detachment occurs via a retro-Diels-Alder reaction within minutes.