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.

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.

Poly(butylene adipate-co-succinate) (PBAS), a saturated aliphatic polyester cured by dicumyl peroxide (DCP), was prepared and the viscoelastic property was investigated. The viscosity of crosslinked PBAS increased, and it exhibited rubbery behavior as the content of curing agent was increased. The results suggested that the viscosity and elasticity of PBAS could be regulated by adding a small amount of DCP; hence, the processibility could be improved. Prior to foaming, a proper formulation of blowing agent (blowing agent/urea activator ϭ 100:8 phr) was examined to prepare expanded PBAS foam. Low-density PBAS expanded foams were prepared using a chemical blowing agent and DCP. The effect of the foaming temperature, additive content, and curing agent content on the blowing ratio and morphology of expanded PBAS foams was investigated. A closed-cell structure PBAS foam of high blowing ratio (density about 0.05 g/cm 3 ) could be obtained by adding 3 phr DCP. To manufacture expanded PBAS foam under 0.1 g/cm 3 using a chemical blowing agent, the storage modulus of the matrix polymer should exceed the loss modulus by enough to stabilize growing bubbles.

We attempted to introduce crosslinking into poly(butylene adipate-co-succinate) (PBAS) to improve the properties, such as the mechanical strength and elasticity, by a simple addition of dicumyl peroxide (DCP). Prior to curing, the thermal stability of PBAS was investigated. Above 170°C PBAS was severely degraded, and the degradation could not be successfully stabilized by an antioxidant. The PBAS was effectively crosslinked by DCP, and the gel fraction increased as the DCP content increased. A major structure of the crosslinked PBAS was an ester and aliphatic group. The tensile strength and elongation of PBAS were improved with an increasing content of DCP, but there was little affect on the tear strength. The biodegradability of crosslinked PBAS was not seriously deteriorated. A higher degree of crosslinking gave a lower heat of crystallization and heat of fusion. However, the melt crystallization temperatures of the crosslinked PBAS were higher than that of PBAS.

Poly(ethylene terephthalate) (PET) is one of the most popular thermoplastics for daily use and finds application in packaging products for food and beverage storage, as well as textile materials for clothing. 1 The important features of PET, such as shatterproof nature, high strength to weight ratio, low cost, and recyclability make it feasible for use at the industrial scale for the aforementioned products. 2,3 In addition, PET shows flexible processability as well as moderate mechanical durance and physicochemical stability when in direct contact with body fluids; hence, it is a promising biomaterial for the development of medical products, including implantable devices, vascular grafts, and biosensors. 4,5 However, PET has poor biocompatibility, which results from non-specific binding to proteins because of its inherent hydrophobicity. 6 For example, non-specific protein adsorption onto a sensing platform would decrease the signal-to-noise ratio and reduce the sensitivity for target detection. 7 In the case of medical implants, adsorption of fibrinogen and platelet adhesion can cause immune responses, limiting their applications. 8 The most effective and general approach to reduce non-specific binding of proteins in the coating method is to form a hydrophilic polymer brush onto the surface of interest via a two-step process: functionalization of the initiator onto the target surface, and then, polymer brush formation by surface-initiated atom transfer radical polymerization (SI-ATRP) under airtight conditions. 9 However, there are several concerns regarding the use of the conventional protocol on PET substrates in biomedical applications. First, chemical inertness of PET is relatively difficult to be functionalized by initiators compared to other well-known surface chemistry, such as thiols on golds and silanes on oxides. 10 Second, the substrates for PET-based biomedical devices are not limited to small planar ones, but vary in size, shape, and curvature. This makes deoxygenation in the conventional SI-ATRP process difficult, where the presence of air can lead to early radical termination. Therefore, an alternative strategy is required to realize PET substrates with non-fouling properties for biomedical applications.In this work, we report aryl azide-based photochemical methods to immobilize the initiator, followed by activators regenerated by electron transfer (ARGET) for ATRP that Communication