Abstract
The implementation of photoswitches within polymers offers an exciting toolbox in the design of light‐responsive materials as irradiation can be controlled both spatially and temporally. Herein, we introduce a range of water‐soluble copolymers featuring naphthol‐based chromophores as photoacids in the side chain. With that, the resulting materials experience a drastic increase in acidity upon stimulation with UV light and we systematically studied how structure and distance of the photoacid from the copolymer backbone determines polymerizability, photo‐response, and photostability. Briefly, we used RAFT (reversible addition–fragmentation chain transfer) polymerization to prepare copolymers consisting of nona(ethylene glycol) methyl ether methacrylate (MEO9MA) as water‐soluble comonomer in combination with six different 1‐naphthol‐based (“N”) monomers. Thereby, we distinguish between methacrylates (NMA, NOeMA), methacrylamides (NMAm, NOeMAm), vinyl naphthol (VN), and post‐polymerization modification based on [(1‐hydroxynaphthalen‐2‐amido)ethyl]amine (NOeMAm, NAmeMAm). These P(MEO9MAx‐co‐“N”y) copolymers typically feature a 4:1 MEO9MA to “N” ratio and molar masses in the range of 10 kg mol−1. After synthesis and characterization by using NMR spectroscopy and size exclusion chromatography (SEC), we investigated how potential photo‐cleavage or photo‐degradation during irradiation depends on the type and distance of the linker to the copolymeric backbone and whether reversible excited state proton transfer (ESPT) occurs under these conditions. In our opinion, such materials will be strong assets as light‐mediated proton sources in nanostructured environments, for example, for the site‐specific creation of proton gradients. We therefore exemplarily incorporated NMA into an amphiphilic block copolymer and could demonstrate the light‐mediated release of Nile red from micelles formed in water as selective solvent.
Highlights
Various research fields benefit from advances in the design of molecular photoswitches,[1] as light offers considerable advantages over other triggers including the possibility to control chemistry both spatially and temporally
In 2017 we reported in a proof-of-concept study on the incorporation of 1-naphthol-based photoacids into statistical terpolymers and could show that irradiation with light led to a drastic increase in hydrophilicity.[33]
A set of copolymers containing 1naphthol derivatives substituted in position five were prepared leading to the respective methacrylate, that is, 1-naphthol-5methacrylate (NMA), and the respective methacrylamide (1naphthol-5-methacrylamide, NMAm, Figure 1 A)
Summary
Various research fields benefit from advances in the design of molecular photoswitches,[1] as light offers considerable advantages over other triggers (e.g., temperature or pH) including the possibility to control chemistry both spatially and temporally. Such photoswitches predominantly comprise organic chromophores such as azobenzenes,[2] spiropyrans,[3] and diarylethenes,[4] and have so far been used in, for example, energy storage, chemical sensing, or in controlling both the conformation and the activity of biomolecules.[5]. Schacher Jena Center for Soft Matter (JCSM) Friedrich Schiller University Jena Philosophenweg 7, 07743 Jena (Germany)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
