Post-Polymerisation Modification of Polyolefins through C-H bond Activation by Frustrated Radical Pairs

Oxyfunctionalised polyolefins are highly attractive materials, as they can expand the property space for polyolefins – improving for example adhesion properties or compatibility with other (polar) materials or enabling the introduction of reactive handles for improved end-of-life management, while keeping the advantageous characteristics of pristine polyolefins intact. In this work we report on the use of frustrated radical pair (FRP) chemistry to introduce ketones and aldehydes onto the backbone of polyethylene and polypropylene materials. Using a disilazide donor and an N-oxoammonium acceptor, the FRP activate the C–H bonds of these polyolefins, after which the aminoxylated intermediates are oxidised in one-pot with mCPBA to yield the oxyfunctionalised polymer. Selective C–H functionalisation of polyolefins thus introduces oxyfunctional groups onto PE (HDPE, 0.3%) and, remarkably, also onto the more challenging isotactic PP (0.6%). Promisingly, this radical chemistry approach does not induce any backbone chain scission or crosslinking on both polymers tested. Upon oxyfunctionalisation the polymers retain the thermal properties of the pristine polyolefins while incorporating a small fraction of polar ketones, which hold the potential for further downstream recycling or photochemical degradation.