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Introducing functionality onto PE surfaces is a longstanding challenge in polymer science, driven by the need for polymer materials with improved adhesion and antifouling properties. Herein, we report surface-initiated hydrogen atom transfer-reversible addition−fragmentation chain transfer(SI HAT RAFT) as a robust method to grow high-density brush polymers from PE surfaces. 

Photoacid generators (PAGs) have facilitated a number of technology breakthroughs in the electronic, coating, and additive manufacturing industries. Traditionally, PAGs that contain weakly coordinating anions, such as PF6-, generate Brønsted superacids under UV irradiation for rapid cationic polymerizations. However, PAGs with strongly coordinating anions remain under-utilized as they form weak acids that are inefficient or even incapable of initiating polymerization. To expand the scope of potential counteranions in PAGs, we leveraged a thiophosphoramide hydrogen bond donor (HBD) to catalyze photoinitiated cationic polymerizations from diphenyliodonium PAGs. Through the formation of hydrogen bonds between the HBD and PAG counteranion, acceleration of the polymerization rate was observed for a range of non-coordinating and coordinating anions. The effect of the HBD on the polymerization kinetics was investigated by 1H-NMR titrations and geometry optimizations. Extending HBD catalysis beyond photopolymerizations, addition of HBD also enabled hydrochloric acid to initiate controlled reversible addition-fragmentation chain transfer (RAFT) polymerization under ambient conditions. With the versatility of HBD, there is potential to access initiation systems that were previously believed to be impractical for cationic polymerization. 

Abstract Leveraging electrochemistry to degrade robust polymeric materials has the potential to impact society's growing issue of plastic waste. Herein, we develop an electrocatalytic oxidative degradation of polyethers and poly(vinyl ethers) via electrochemically mediated hydrogen atom transfer (HAT) followed by oxidative polymer degradation promoted by molecular oxygen. We investigated the selectivity and efficiency of this method, finding our conditions to be highly selective for polymers with hydridic, electron‐rich C−H bonds. We leveraged this reactivity to degrade polyethers and poly(vinyl ethers) in the presence of polymethacrylates and polyacrylates with complete selectivity. Furthermore, this method made polyacrylates degradable by incorporation of ether units into the polymer backbone. We quantified degradation products, identifying up to 36 mol % of defined oxidation products, including acetic acid, formic acid, and acetaldehyde, and we extended this method to degrade a polyether‐based polyurethane in a green solvent. This work demonstrates a facile, electrochemically‐driven route to degrade polymers containing ether functionalities. 

Cationic reversible addition–fragmentation chain transfer (RAFT) polymerizations have permitted the controlled polymerization of vinyl ethers and select styrenics with predictable molar masses and easily modified thiocarbonylthio chain ends. However, most cationic RAFT systems require inert reaction conditions with highly purified reagents and low temperatures. Our groups recently developed a living cationic polymerization that does not require these rigorous conditions by utilizing a strong organic acid (pentacarbomethoxycyclopentadiene (PCCP)) and a hydrogen bond donor. By combining our PCCP acid promoted polymerization with a chain transfer agent, we have designed a tolerant cationic RAFT system that can be performed neat, open to the air, and at room temperature. Additionally, this system allows us to utilize catalytic amounts of the PCCP acid to furnish polymers with chain end functionality that can be easily isolated and further manipulated to make functional materials.