Development of Low Temperature Activatable Aryl Azide Adhesion Promoters as Versatile Surface Modifiers

Area of Science:

• Materials Science
• Organic Chemistry
• Surface Chemistry

Background:

• Adhesion promoters create chemical bridges for permanent surface modification.
• Existing methods using perfluoro-aryl azides require high temperatures (>100 °C) or are photolytically unfeasible.
• There is a need for adhesion promoters that activate at lower temperatures for broader material compatibility.

Purpose of the Study:

• To design and synthesize novel aryl azides with tunable, lower activation temperatures.
• To enable covalent attachment of polymers lacking reactive groups to surfaces under mild conditions.
• To demonstrate the efficacy of these new adhesion promoters for surface functionalization.

Main Methods:

• Computational modeling using density functional theory (DFT) to predict activation temperatures.
• Synthesis of three substituted aryl azide molecules.
• Experimental validation of thermal activation temperatures and C-H insertion reactions.
• Incorporation of synthesized molecules into polymeric backbones to create adhesion promoters.
• Surface functionalization with polyvinylpyrrolidone (PVP) films.
• Characterization using spectroscopic ellipsometry (ELM) and X-ray photoelectron spectroscopy (XPS).

Main Results:

• Substituent variation effectively tunes aryl azide activation temperatures below 100 °C.
• The difluoro-substituted p-phenoxy azide demonstrated reactivity around 70 °C via C-H insertion.
• Synthesized adhesion promoters facilitated covalent attachment of PVP films to substrates.
• Successful immobilization of PVP films under mild thermal activation conditions was confirmed.

Conclusions:

• Novel aryl azides offer a pathway to low-temperature surface functionalization.
• The developed adhesion promoters enable robust covalent attachment of polymers to various surfaces.
• This approach expands the utility of adhesion promoters for sensitive materials and applications, including medical devices.