Light-Induced Step-Growth Polymerization of AB-Type Photo-Monomers at Ambient Temperature

Abstract

We introduce two AB-type monomers able to undergo a facile catalyst-free photoinduced polycycloaddition of photocaged dienes, enabling rapid Diels–Alder ligations under UV-irradiation (λmax = 350 nm) at ambient temperature, closely adhering to Carother’s equation established by a careful kinetic study (17800 g mol–1 < M w < 24700 g mol–1). The resulting macromolecules were in-depth analyzed via size exclusion chromatography (SEC) and nuclear magnetic resonance (NMR) spectroscopy. Additionally, SEC hyphenated to high resolution-electrospray ionization-mass spectrometry (HR-ESI-MS) enabled the careful mapping of the end group structure of the generated polymers. Furthermore, we demonstrate that both monomer systems can be readily copolymerized. The study thus demonstrates that Diels–Alder ligation resting upon photocaged dienes is a powerful tool for accessing step-growth polymers.

Visible Light Catalyzed Step‐Growth Polymerization through Mizoroki–Heck Coupling Reaction

“…Apart from the chain growth polymerization systems, photo‐induced step growth polymerizations are also emerging as an increasingly attractive topic in polymer synthesis. Various photoreactions or photoinduced reactions, such as thiol‐ene reaction,9 photodimerization of cinnamates or coumarinates,10 photodimerization of 2‐furanacrylates,11 photoinduced electron transfer of iodonium salt,12 light induced nitrile imine‐mediated tetrazole‐ene cycloaddition (NITEC),13 UV‐light induced Diels–Alder reaction,14 etc., have been used for step growth polymerizations. In addition, AB‐type of monomers possessing aliphatic hydroxyl and photo labile benzodioxinones (as masked COOH) was also used for the synthesis of oligo polyester as a demonstration of the concept of photo induced step growth polymerization 15.…”

Visible Light Induced Step‐Growth Polymerization by Substitution Reactions

“…[ 16–21 ] By taking advantage of the advanced state of the conventional approaches, recent research interest in synthetic polymer chemistry is directed to adapt photoinduced reactions to step‐growth polymerization. Generally applied light induced strategies include cycloaddition [ 17,18 ] and selected organic reactions [ 19–22 ] or consequential electron transfer and radical coupling processes. The latter can be achieved by the use of conjugated aromatic structures as monomers and onium salts with appropriate oxidation potentials and non‐nucleophilic counter ions as oxidants.…”

Visible‐Light‐Induced Passerini Multicomponent Polymerization

“…Because of the high reactivity and short lifetimes of photogenerated thioaldehydes, as well as the complex nature of photoinduced MCPs, an in‐depth understanding of the relationship between the synthetic conditions as well as product yield and purity is critical to successfully develop a robust visible‐light‐induced MCP methodology . Our research team has recently demonstrated that qualitative stochastic or kinetic Monte Carlo ( k MC) screening is indispensable in order to understand complex reaction mechanisms and for controlling selectivity toward a targeted product .…”