Antifouling Surface Coating Using Droplet-Based SI-ARGET ATRP of Carboxybetaine under Open-Air Conditions.

The formation of a dense zwitterionic brush through surface-initiated atom transfer radical polymerization (SI-ATRP) is a typical graft-from approach used to achieve antifouling surfaces with high fidelity; however, their air-tightness may cause inconvenience to users. In this context, activator regenerated by electron transfer (ARGET) ATRP is emerging as an alternative surface-coating tool because limited amount of air is allowed to form a dense polymer brush. However, the degree of air tolerance that can ensure a thick polymer brush has not been clearly defined, limiting its practical usage under ambient-air conditions. In this study, we investigated the SI-ARGET ATRP of carboxybetaine (CB) by changing the air conditions, along with the air-related parameters, such as the concentration of the reducing agent, the volume of the polymerization solution (PS), or the solvent composition, and correlated their effects with the poly(CB) thickness. Based on the optimized reaction conditions, a poly(CB) brush with reliable thickness was feasibly formed even under open-air conditions without a degassing step. In addition, a microliter droplet (∼100 µL) of PS was sufficient to proceed with the SI-ARGET ATRP for the covering of a poly(CB) brush on the surface area of interest. By applying an optimized SI-ARGET ATRP of CB, antifouling was feasibly achieved in the surface region of interest using an array to form a large surface area under fully exposed air conditions. In other words, optimized SI-ARGET ATRP enabled the formation of a thick poly(CB) brush on the surfaces of various dimensions under open-air conditions.

Surface-Initiated ARGET ATRP of Antifouling Zwitterionic Brushes Using Versatile and Uniform Initiator Film.

In this study, we developed a uniform initiator layer that can be formed on various surfaces, and formed site-selectively, for the subsequent antifouling polymer brush formation. Initially, metal-organic films composed of tannic acid (TA) and FeIII ions (TA-FeIII) were formed on various surfaces, followed by functionalization with an aryl azide-based initiator (ABI) under photoreaction. In particular, combination with a photolithographic technique enabled the presentation of initiators only on the intended region within a single-surface platform. A resultant initiator film (TF-ABI) was formed under mild reaction conditions and meets the uniformity and transparency requirements concurrently. Subsequently, we showed that TF-ABI can be further utilized to form a polymer brush by proceeding with surface-initiated polymerization using a zwitterionic monomer, namely, sulfobetaine acrylamide (SBAA). Instead of applying a classical, yet air-sensitive atom transfer radical polymerization (ATRP) technique, we utilized an activator regenerated by electron transfer (ARGET) ATRP under air conditions without a cumbersome deoxygenation step. Overall, our initiator layer allowed the antifouling poly(SBAA) brush to be used on various surfaces, and enabled their pattern generation.

Development of Stimulus-Responsive Degradable Film via Codeposition of Dopamine and Cystamine.

Herein, we report a degradable film that can be coated on various substrates by the codeposition of dopamine and cystamine. The thickness of the resulting film (pDC) varies depending on the initial ratio of dopamine/cystamine dissolved in a solution; the thickest film (ca. 60 nm) is obtained under optimized codeposition conditions. Selective degradation of pDC occurs in the presence of tris(2-carboxyethyl)phosphine (TCEP), the reaction kinetics of which are highly dependent on the TCEP concentration. For further application as a drug-delivery platform, doxorubicin can be loaded within the pDC film, which is released actively under film degradation in response to TCEP. We expect that the developed pDC film will be a useful tool for developing drug delivery cargo, antibacterial surface, and cell surface coating for various biomedical applications.