Controlling Chain Coupling and Single‐Chain Ligation by Two Colours of Visible Light

Abstract

While photochemical synthesis offers access to spatiotemporal reaction control, its potential to selectively address specific reactions by the colour of light is usually limited by ubiquitous spectral absorption overlaps of the reactive groups.H erein, an ew concept is introduced that actively suppresses one ligation reaction by triggering the cycloreversion of the [2+ +2] cycloaddition of styrylpyrene. Combination of the photoreversible styrylpyrene chemistry with the [4+ +4] cycloaddition of 9-triazolylanthracene makes it possible to initially induce chain coupling using UV light and to subsequently ligate the formed single-chain nanoparticle (SCNP) with asecond polymer chain using blue light. Seizing upon the first sequence-independent l-orthogonal reactivity established here,t he same macromolecular architecture was obtained in reverse irradiation sequence,b yb lue and subsequent violet light irradiation-completely foregoing highenergy UV light.

Time‐Dependent Differential and Integral Quantum Yields for Wavelength‐Dependent [4+4] Photocycloadditions

“…By using mild visible light to exert photoreactions, photodamage of the surrounding matrix and biological tissue typically caused by UV light can be avoided. To initiate [4+4] cycloadditions outside of the classically applied UV regime with mild visible light, extension of the conjugated system in order to affect the HOMO–LUMO gap has proven to be a successful strategy . However, the required functionalization of A (R group in Figure ) increases the synthetic complexity.…”

Effect of intramolecular crosslinker properties on the mechanochemical fragmentation of covalently folded polymers

“…Yet, the most stable SCPNs measured in this study were CL1‐32 and CL3‐4 ; the first produced by folding the polymer with a long oligoethylene glycol diacrylate and regularly folded in toluene, which allows the connection of the CL to distant AEMA units. These results highlight the importance in developing synthetic techniques that provide control over which monomers are connected during intramolecular collapse …”

Macromolecular Superstructures: A Future Beyond Single Chain Nanoparticles

“…As a consequence, it is now possible to either trigger the reaction of the pendant anthracene units to induce the SCNP folding, or the interchain association through the terminal styrylpyrene. Importantly both reactions could be triggered subsequently and in any given order, only depending on the color of light …”

“…Importantly both reactions could be triggered subsequently and in any given order, only depending on the color of light. [90] The developed concept of sequence independent orthogonal ligation chemistry was readily applied to generate spatially resolved polymer coatings from a single multi material Since the 9-triazolylanthracene dimerization can only be initiated by irradiation at λ = 330 and 410 nm, while the styrylpyrene dimerization can be initiated at λ = 410 and 455 nm and reverted at λ = 330 nm, selective triggering of the two dimerization reactions becomes accessible: Initial irradiation at λ = 330 nm suppresses the reaction of the terminal photoreactive group, yet initiates the SCNP folding. The obtained SCNP1 can subsequently be ligated with a second polymer chain also a containing terminal styrylpyrene unit to form SCNP1-co-PEG at λ = 455 nm.…”