Efficient synthesis of bottle-brush polymers enabled by selective photoactivation strategy in NIR-induced PET-RAFT polymerization

Bottle-brush polymers possessing densely grafted side chains have special properties that are distinct from linear macromolecules.Herein,an efficient method for preparing bottle-brush polymers based on a selective photoactivation strategy in the photoinduced electron/energy transfer reversible addition-fragmentation chain transfer（PET-RAFT） polymerization was developed.A methacrylate monomer 2-(2-（dodecylthiocarbonothioylthio）propionate)ethyl methacrylate（DTPEMA） containing a 2-（dodecylthiocarbonothioylthio）propionate（DTP） unit with a secondary R group was designed.Utilizing the unique selectivity of metal naphthalocyanine photocatalyst zinc 2,11,20,29-tetra-tert-butyl-2,3-naphthalocyanine（ZnTtBNc） toward trithiocarbonate with tertiary R group,the PET-RAFT polymerization of DTPEMA catalyzed by ZnTtBNc was performed under near infrared（NIR） light(λmax=760 nm) irradiation at room temperature,using 4-cyano-4-[（dodecylsulfanylthiocarbonyl）-sulfanyl]pentanoic acid（CDTPA） with a tertiary R group as a chain transfer agent（CTA）.Proton nuclear magnetic resonance（1H NMR）and gel permeation chromatography（GPC） results demonstrated that the DTP units in the side chains were inert during the polymerization.By grafting poly（methyl acrylate）(PMA) from PDTPEMA via thermal-initiated RAFT polymerization,welldefined P（DTPEMA-g-PMA） bottle-brush polymers could be afforded.Furthermore,the film prepared from the bottle-brush polymer exhibited excellent scratch self-healing property due to the interlocking of side chains.