α,ω-Reactive Building Blocks Based on a Dual Functional RAFT Agent for Thermal and Light-Induced Ligation

A dual functional chain transfer agent (CTA) capable of highly efficient sequential thermal and photo-induced ligation, generating alpha,omega-functional polymers, is introduced. The newly designed CTA (1-(4-((2-formyl-3-methyl phenoxy)methyl)phenyl)ethyl (diethoxyphosphoryl)methane dithioate) fuses thermally triggered hetero Diels-Alder chemistry with rapid light-induced photoenol chemistry. The versatility of the CTA is exemplarily demonstrated via the preparation of an amphiphilic triblock quaterpolymer poly-(isoprene-co-styrene)-block-poly(ethyl acrylate)-block-poly(ethylene oxide) (P(I-co-S)-b-PEA-b-PEO). Subsequent to the homopolymerization of ethyl acrylate (PEA), a Cp-functional poly(isoprene-co-styrene) (P(I-co-5)) is conjugated with the electron-deficient C=S double bond (dienophile) of the CTA end group, generating a P(I-co-S)-b-PEA diblock terpolymer. The triblock quaterpolymer P(I-co-S)-b-PEA-b-PEO is generated by photoligation of a macromolecular dienophile, i.e., the fumarate-terminated poly(ethylene oxide) (PEO-fum) to the photoenol-functional P(I-co-S)-b-PEA. The new dual functional ligation RAFT agent constitutes a technology platform for generating alpha,omega-reactive building blocks from one single chain transfer agent.