Contemporary Photoligation Chemistry: The Visible Light Challenge.

Catalyst-free and bond-forming light-induced reactions have seen an unprecedented renaissance in the realm of soft matter materials science due to their efficiency, spatio-temporal controllability and, sometimes, photoreversible nature. However, many of these reactions rely on the application of high energy UV light that can cause photo-degradation and is inapplicable in biological environments. If up-conversion systems or two-photon processes are to be avoided, strategies for red-shifting catalyst-free ligation technology are critically required.

Photochemically Induced Folding of Single Chain Polymer Nanoparticles in Water.

We pioneer the synthesis of fluorescent single chain nanoparticles (SCNPs) via UV-light induced folding based on tetrazole chemistry directly in pure water. Water-soluble photoreactive precursor polymers based on poly(acrylic acid) (PAA) bearing tetrazole, alkene and tetraethylene glycol monomethyl ether moieties, (PAA(Tet/p-Mal/TEG)), or simply tetrazoles moieties, PAA(Tet), were generated via RAFT polymerization. While tetrazole, ene, and acrylic acid containing polymers fold via dual nitrile imine-mediated tetrazole-ene cycloaddition (NITEC) as well as nitrile imine-carboxylic acid ligation (NICAL), tetrazole and acrylic acid only functional prepolymers fold exclusively via NICAL.

Degradable fluorescent single-chain nanoparticles based on metathesis polymers.

We introduce the facile synthesis of fluorescent single-chain nanoparticles (SCNPs) based on chain-shattering acyclic diene metathesis (ADMET) polymers featuring self-immolative azobenzene motifs. An electrophilic alkoxyetherification is utilized to introduce the photoreactive moieties required for the subsequent chain collapse via UV-induced nitrile imine-mediated tetrazole-ene cycloaddition (NITEC).

Polybutadiene Functionalization via an Efficient Avenue.

We introduce a facile and quantitative postpolymerization functionalization methodology for 1,4-polybutadienes, allowing us to decorate their pendent alkene functionalities with bromine and alkoxyether motifs carrying an array of functional groups ranging from tetrazoles to pyrenes. Specifically, the approach makes use of a mild, metal-free, electrophilic cascade reaction employing -bromosuccinimide (NBS), a cyclic ether (i.e.