Abstract
Pentafluorophenyl (PFP) esters are widely employed in post-polymerization modification (PPM) techniques due to their high reactivity and quantitative conversion with common nucleophiles. Herein, the activated ester polymer poly(pentafluorophenyl lipoate) (pPFPL) is obtained through quantitative initiator-free photopolymerization and is demonstrated to be a reactive homopolymer scaffold for post-polymerization functionalization. PPFPL was modified quantitatively with isopropyl amine, benzyl amine, and PEG methyl ether amine to afford lipoamide homopolymers exhibiting glass transition temperatures ranging from −57 °C to 73 °C. Functionalization with amine mixtures of PEG amine and benzyl amine afforded thermoresponsive copolymers with sharp tunable LCST transitions. Crosslinking of pPFPL with a diamine (feed ratio 0.1–50%) followed by quenching of residual PFP esters with PEG amine gave polylipoamide hydrogels, characterised by swelling and rheological studies. Both the unimeric polylipoamides as well as the networks could be degraded by virtue of their labile backbone disulfides. Interestingly, oxidative conditions were more efficient than reductive conditions, with oxone treatment giving up to 83% reduction in SEC-measured molar mass and hydrogels undergoing full dissolution in water. Overall, pPFPL is established as a versatile, reactive and modifiable platform for designing degradable lipoamide-based materials.
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•First photo-homopolymerization of an activated ester-functional cyclic disulfide.•Quantitative uncatalyzed amidation of side chains.•Simple access to degradable polymers with tuneable LCST in water.•Synthesis of degradable hydrogels cleavable through reduction and oxidation.