#ABOUT PET FLOW SERIES#
To this aim, we investigated and compared the properties of a series of polymer brushes obtained by SI-PET-RAFT in continuous flow and no-flow conditions, using X-ray photoelectron spectroscopy (XPS), ellipsometry, and single-molecule force spectroscopy (SMFS). The current paper aims for precisely that: the combination of the SI-PET-RAFT technique with flow polymerization, in order to introduce better control to the polymerization. In view of our overall goal to generate with increased precision polymer brushes for bioactive surfaces, 19,39 we were thus interested to see whether also in-flow variations of SI-PET-RAFT could be developed. 36–38 The main benefits of applying flow chemistry in polymer synthesis include improved synthetic precision, improved performance in photopolymerization reactions. 16,18,20,22Ī very recent development in CRPs techniques, particularly RAFT, is the introduction of flow chemistry. For example, we showed it can proceed in an aqueous solution containing an edible photocatalyst, 16,18,20,22 and allows for the visible-light-induced patterned growth of complex polymer brushes in a controlled fashion in the presence of oxygen in the water. 16,18,20,35 This technique requires only simple and mild conditions. 32–35 We and others further developed this method to be applied to surfaces, labelled surface-initiated PET-RAFT, or SI-PET-RAFT, to create polymer brushes with increasing levels of functionality. In RAFT-based techniques, this invoked the use of photoinduced electron transfer-reversible addition–fragmentation chain transfer (PET-RAFT). The next step in the evolution of surface-initiated CRPs (SI-CRP) was the introduction of light as a reaction-inducing trigger. In addition, the technique does not require heavy metals and can be applied to create polymer brushes via immobilization of the RAFT agent on the surface. The reversible addition–fragmentation transfer polymerization (RAFT), 30 which typically uses a thiocarbonylthio moiety, is one the most versatile and widely used methods for polymer synthesis. Those aspects hamper further bioapplications and scaling-up. 7 However, frequently encountered disadvantages of those techniques include the use of heavy metals and the need for an oxygen-free environment during synthesis.
#ABOUT PET FLOW ACTIVATOR#
Surface-initiated atom transfer radical polymerization (SI-ATRP) 13,17 and related variations of RDRP, such as supplemental activator and reducing agent (SARA), 28 single-electron transfer-living radical polymerizations (SET-LRP), 29 and light-triggered living radical polymerization (LT-LRP), 19 are among the most common techniques to make polymer brushes, and with significant success. 26,27 Those and many other applications make polymer brush-based coatings uniquely positioned for the development of widely different fields of application, including improved biosensors, tissue engineering, and biointeractive devices. 12 Polymer brushes have thus been used to make surfaces antifouling, 13–20 antibacterial, 21 antiviral, 22 bioactive, 17 biointeractive, 19,23,24 biomimetic, 25 and/or lubricating. 6,8–11 This characteristic high surface density of polymer brushes often creates unique properties, such as preventing non-specific adsorption of proteins, other polymers, or even larger entities. 6,7 Polymer brushes are characterized by macromolecules being bound in high surface density to a surface by a chain end or ends. 3–5 The introduction of CRPs, along with many other unique applications, also allowed the controlled formation of polymer brushes. Introduction Controlled radical polymerization (CRP), often also known as reversible deactivation radical polymerization (RDRP) techniques, 1,2 provide unique means to tune the molecular weight, dispersity, block sequence, and molecular architecture of synthetic polymers. We further show the linear correlation between the molecular weight of the polymer brush and its dry thickness by combining ellipsometry and single-molecule force spectroscopy. The improved control compared to no-flow conditions provides prolonged linear growth of the polymer brush (up to 250 nm, where no-flow polymerization maxed out <50 nm), and improved polymerization control of the polymer brush that allows the construction of diblock polymer brushes. We confirm the composition and topological structure of the brushes by X-ray photoelectron spectroscopy, ellipsometry, and AFM. Here we introduce improved control over SI-PET-RAFT polymerizations via continuous flow conditions. Surface-initiated photoinduced electron transfer-reversible addition–fragmentation chain transfer (SI-PET-RAFT) provides a light-dependent tool to synthesize polymer brushes on different surfaces that tolerates oxygen and water, and does not require a metal catalyst.
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