UV and NIR-Responsive Layer-by-Layer Films Containing 6-Bromo-7-hydroxycoumarin Photolabile Groups

Area of Science:

• Materials Science
• Photochemistry
• Polymer Chemistry

Background:

• Layer-by-layer (LbL) assembly is a versatile technique for fabricating multilayer films.
• Photodegradable materials are crucial for applications requiring controlled disassembly.
• Understanding film stability requires analyzing inter-chain interactions like ion-pairing and hydrophobic forces.

Purpose of the Study:

• To develop polyelectrolyte multilayer films that can be dissolved using light.
• To investigate the mechanism of light-induced film dissolution.
• To explore the role of pH and inter-chain interactions in film stability and dissolution.

Main Methods:

• Fabrication of polyelectrolyte multilayer films using the layer-by-layer (LbL) technique.
• Incorporation of photocleavable 6-bromo-7-hydroxycoumarinyl ester groups and N,N-dimethylaminoethyl methacrylate (DMAEMA) into a methacrylic copolymer.
• Exposure of films to ultraviolet (UV) and near-infrared (NIR) light to induce photochemical deprotection and dissolution.
• Investigation of film stability as a function of pH in both irradiated and unirradiated states.

Main Results:

• Successfully prepared LbL films that undergo dissolution upon exposure to UV or NIR light.
• Demonstrated that film dissolution is driven by photochemical deprotection of the copolymer.
• Established that film stability is pH-dependent, highlighting the importance of disrupting ion-pairing and hydrophobic interactions for complete dissolution.
• Confirmed that the coumarinyl ester groups possess significant two-photon photolysis cross sections, enabling nonlinear photochemical processes.

Conclusions:

• Developed novel photolabile LbL films with tunable dissolution properties triggered by light.
• Provided fundamental insights into the photochemistry and stability of LbL films.
• Expanded the application potential of photolabile LbL films to nonlinear photochemical processes.