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Azide Photochemistry in Acrylic Copolymers for Ultraviolet Cross-Linkable Pressure-Sensitive Adhesives: Optimization,
Rohani Abu Bakar1,2, Yuman Li3, Oliver P Hewitson3
1Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH, U.K.
ACS Applied Materials & Interfaces
|June 23, 2022
Summary
Researchers developed a novel photo-switchable pressure-sensitive adhesive (PSA) using perfluorophenylazide chemistry. This new material allows precise control over adhesion properties, enabling tunable cross-linking for advanced applications.
Area of Science:
- Polymer Chemistry
- Materials Science
- Adhesive Technology
Background:
- Pressure-sensitive adhesives (PSAs) rely on viscoelastic copolymers, with properties tuned by comonomer ratios, molecular weights, and cross-link densities.
- Traditional methods for cross-linking PSAs often involve external photoinitiators, which can complicate the formulation and application process.
- Precise control over cross-linking is crucial for optimizing PSA performance, including tack, peel adhesion, and shear resistance.
Purpose of the Study:
- To introduce perfluorophenylazide chemistry as a novel method for precisely controlling polyacrylate network formation in PSAs.
- To investigate the photo-switchable properties of these azide-modified copolymers and their impact on adhesion characteristics.
- To demonstrate the potential for creating functionalized PSAs through post-polymerization modification.
Main Methods:
- Synthesis of poly(n-butyl acrylate-co-2,3,4,5,6-pentafluorobenzyl acrylate) [poly(PFBA-co-BA)] copolymers.
- Post-polymerization modification to introduce photo-reactive azide groups, creating azide-modified poly(PFBA-co-BA).
- UV irradiation to induce C-H insertion cross-linking via nitrene intermediates, followed by characterization of adhesive properties (shear, tack, peel).
Main Results:
- UV irradiation of azide-modified copolymers led to covalent cross-linking, enabling photo-switchable adhesion.
- High azide content resulted in strong shear resistance but reduced tack and peel adhesion due to excessive cross-linking.
- Optimal probe tack adhesion was observed at 0.3 mol% azide content, and optimal peel adhesion at 0.5 mol% azide content.
- Demonstrated successful dye-functionalization of the PSA via a multicomponent reaction, retaining adhesive properties.
Conclusions:
- Perfluorophenylazide chemistry provides an effective, initiator-free method for precise cross-linking control in PSAs.
- The developed materials exhibit tunable photo-switchable adhesion properties based on azide content and UV exposure.
- This platform offers significant potential for designing advanced, functionalized pressure-sensitive adhesives.
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