Arylazopyrazole-Modified Thiolactone Acrylate Copolymer Brushes for Tuneable and Photoresponsive Wettability of Glass Surfaces

Abstract

Photoswitches have long been employed in coatings for surfaces and substrates to harness light as a versatile stimulus to induce responsive behavior. We previously demonstrated the viability of arylazopyrazole (AAP) as a photoswitch in self-assembled monolayers (SAMs) on silicon and glass surfaces for photoresponsive wetting applications. We now aim to transfer the excellent photophysical properties of AAPs to polymer brush coatings. Compared to SAMs, polymer brushes offer enhanced stability and an increase of the thickness and density of the functional organic layer. In this work, we present thiolactone acrylate copolymer brushes which can be post-modified with AAP amines as well as hydrophobic acrylates, making use of the unique chemistry of the thiolactones. This strategy enables photoresponsive wetting with a tuneable range of contact angle change on glass substrates. We show the successful synthesis of thiolactone hydroxyethyl acrylate copolymer brushes by means of surface-initiated atom-transfer radical polymerization with the option to either prepare homogeneous brushes or to prepare micrometer-sized brush patterns by microcontact printing. The polymer brushes were analyzed by atomic force microscopy, time-of-flight secondary ion spectrometry, and X-ray photoelectron spectroscopy. Photoresponsive behavior imparted to the brushes by means of post-modification with AAP is monitored by UV/vis spectroscopy, and wetting behavior of homogeneous brushes is measured by static and dynamic contact angle measurements. The brushes show an average change in static contact angle of around 13° between E and Z isomer of the AAP photoswitch for at least five cycles, while the range of contact angle change can be fine-tuned between 53.5°/66.5° (E/Z) and 81.5°/94.8° (E/Z) by post-modification with hydrophobic acrylates.

Multi-Stimuli-Responsive Water-Dispersible Magnetite Nanoparticles Using Arylazopyrazole-Modified Polymer Ligands

“…The syntheses of organic compounds are described in the Supporting Information in detail. TEG-AAP, Ph-AAP, and AAP-CF 3 were prepared as described in the literature. Amide coupling of AAP with pAA was carried out with (benzotriazol-1-yloxytripyrrolidinophosphonium hexafluorophosphate) (PyBOP) and triethylamine in dimethylformamide .…”

Simple photocleavable indoline-based materials for surface wettability patterning

“…There are numerous examples of materials that photoswitch wettability through physical or chemical changes. Photoresponsive compounds, such as azobenzene, 4 spiropyran, 6 diarylethene, 7 and many others, 8,9 have been extensively studied for their ability to reversibly alter surface energy and/or physical geometry upon irradiation. While these reuseable materials have gained significant attention, they generally require extensive and costly synthetic and fabrication techniques, with an overall trend of minimal benefit compared to their complexity.…”

γ-Functional Iminiumthiolactones for the Single and Double Modification of Peptides

“…In a single modification, the heterocyclic carbonyl undergoes chemo- and regioselective amidation, while in the additional presence of a Michael acceptor (e.g., maleimide), a double modification takes place (ring opening, followed by a thiol–X reaction). , The unique reactivity of TLs can be introduced through the commercially available homocysteine thiolactone (HCTL), which can be easily modified through the amine in the α-position (Figure ). Hence, it has been extensively used for postpolymerization modifications, − toward sequence-defined and functional polymers, − surfaces, , hydrogels, , and bioconjugate materials. − …”