Light-fueled dynamic covalent crosslinking of single polymer chains in non-equilibrium states.

Daniel Kodura,Christopher Barner-Kowollik,Anja S Goldmann,Fabian R Bloesser,Hannes A Houck,Hendrik Frisch,Filip E Du Prez

doi:10.1039/d0sc05818a

Daniel Kodura, Christopher Barner-Kowollik + Show 5 more

Open Access

https://doi.org/10.1039/d0sc05818a

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Abstract

While polymer synthesis proceeds predominantly towards the thermodynamic minimum, living systems operate on the reverse principle – consuming fuel to maintain a non-equilibrium state. Herein, we report the controlled formation of 3D macromolecular architectures based on light-fueled covalent non-equilibrium chemistry. In the presence of green light (525 nm) and a bivalent triazolinedione (TAD) crosslinker, naphthalene-containing polymers can be folded into single chain nanoparticles (SCNPs). At ambient temperature, the cycloaddition product of TAD with naphthalene reverts and the SCNP unfolds into its linear parent polymer. The reported SCNP is the first example of a reversible light triggered folding of single polymer chains and can readily be repeated for several cycles. The folded state of the SCNP can either be preserved through a constant supply of light fuel, kinetic trapping or through a chemical modification that makes the folded state thermodynamically favored. Whereas small molecule bivalent TAD/naphthalene cycloaddition products largely degraded after 3 days in solution, even in the presence of fuel, the SCNP entities were found to remain intact, thereby indicating the light-fueled stabilization of the SCNP to be an inherent feature of the confined macromolecular environment.

Highlights

During the last century, the majority of chemical transformations was covalently driven, aiming to approach a thermodynamic minimum.[1]
To apply the photo-Diels–Alder reaction for the non-equilibrium folding of single polymer chains, two copolymers (P1 and P2, Scheme 1b) of methyl methacrylate (MMA) and naphthalenecontaining comonomer were synthesized via reversible addition–fragmentation chain-transfer polymerization (RAFT) (Table 1)
We report an unprecedented light-fueled single polymer chain folding resulting in a covalently bound 3D macromolecular architecture existing in a non-equilibrium state

Summary

Introduction

The majority of chemical transformations was covalently driven, aiming to approach a thermodynamic minimum.[1]. Offline 1H NMR of SCNP2 veri ed that the observed contraction can be attributed to the transformation of the naphthalene side chain moieties into their corresponding TAD/naphthalene cycloadducts, with approximately 45% of naphthalene consumption reached 2 h a er irradiation (d 1⁄4 8.75–8.50 ppm, Fig. S23–S26†).

Results

Conclusion