Ultraviolet Light-Induced Surface-Initiated Atom-Transfer Radical Polymerization

Abstract

UV light-induced surface-initiated atom-transfer radical polymerization (ATRP) was reported. This method uses TiO 2 nanoparticles as photoactive materials to reduce Cu(II)/L to a Cu(I)/L complex under UV irradiation by a one-electron transfer process for ATRP with multiple usage of monomer solutions. The growth of polymer brushes can be manipulated by either varying the content of photoactive materials or regulating the irradiation intensity, thereby yielding polymer brushes with controllable thickness, composition, and architecture. P olymer brushes produced by controlled or living surfaceinitiated radical polymerization 1,2 provide a superior route for surface functionalization, such as creation of smart surfaces, 3−5 antibiofouling materials, 6,7 and lubrication. 8 Compared with various controlled radical polymerization techniques 9 and organic polymer synthesis strategies, 10 atomtransfer radical polymerization (ATRP) 11−14 facilitates the construction of diverse polymer assemblies. 15−18 Generally, a Cu(I)−ligand complex and high monomer concentration are necessary to maximize polymer growth, 19−21 which highly relies on the reversible redox activation/deactivation of Cu(I)/ Cu(II). Control over the Cu(I)/Cu(II) ratio is important to obtain fast a polymerization rate while prolonging the lifetime of propagation chains. 22,23 The scope of ATRP has been expanded to external stimulusinduced polymerizations, 24,25 such as in electrochemically mediated ATRP (eATRP) for controlling polymerization by the electrically one-electron reduction of air-stable Cu(II). 26,27 We extended the eATRP technique to surface-initiated eATRP for controllable fabrication of surface-attached polymer brushes. 28 External visible light-stimulated living radical polymerization has been proposed through the excited Ir(III) species to reduce an alkyl bromide initiator for alkyl radical formation to initiate polymerization, 29,30 click reaction, 31,32 light-mediated atom-transfer radical addition, 33 and photoiniferter-mediated surface attached polymers formation. 34 The key to external stimulus-induced polymerization is continuous in situ generation of the activator catalyst. In this report, we propose a novel approach to achieve surface-initiated ATRP with multiple usage of monomer solutions, wherein the polymerization activators, Cu(I)−ligand, can be continuously generated from a photochemical reduction process by the excited electrons under ultraviolet (UV) illumination that uses the TiO 2 nanoparticle as the photosensitive material. Scheme 1(b) displays the mechanism of UV light-induced ATRP. A commercially available TiO 2 nanoparticle, P25, was

One‐pot synthesis of block copolymers by ring‐opening polymerization and ultraviolet light‐induced ATRP at ambient temperature

“…As shown in Figure , the absorbance of CuBr was under 360 nm which indicated the ATRP of MMA could be induced by UV light at room temperature. The similar phenomenon was also confirmed by others …”

ATRP with a light switch: photoinduced ATRP using a household fluorescent lamp

“…Besides surface-initiated living ionic polymerization, [28][29][30] surface-initiated controlled radical polymerization techniques such as SI-ATRP are very versatile to prepare dened polymer brushes for a multitude of applications. [31][32][33][34] Only recently, Zhou et al 18 reported on the use of UV-light (l ¼ 330 nm at 0.5 or 1.25 mW cm À2 ) and TiO 2 particles as the photosensitizer for the photoinduced surface-initiated ATRP (PSI-ATRP) of different methacrylates from self-assembled monolayers (SAMs) on TiO 2 or gold. However, as thiols are prone to photooxidation by exposure to UV light, 35 it would be benecial to conduct PSI-ATRP with light in the visible range and without addition of particles that might irreversibly contaminate the surfaces.…”

“…Photoinduced ATRP was successfully carried out with single-wavelength light of 392 or 450 nm without photoinitiators, 16 and most recently the use of other light sources and photoinitiator systems has been reported. [17][18][19][20] The signicant photochemical effect of visible light on ATRP of MMA with CuCl/bipyridine as the catalyst has been revealed about one decade ago. 21 The authors concluded that visible light can not only accelerate the polymerization but also improve the livingness of the polymerization at low catalyst levels.…”

Investigation into the photolytic stability of RAFT agents and the implications for photopolymerization reactions

“…RDRPs act by minimizing the time the chain end spends in its 'active' (i.e. Many examples of photochemically-mediated RDRP variants have emerged, including photo-ATRP, [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] photo-NMP, 30 and photo-RAFT (both photoinitiated [31][32][33][34][35][36][37][38] and photo-catalysed [39][40][41][42][43][44][45][46][47] ) with much success. 12 This can be achieved through two fundamental mechanisms: (1) the reversible activation/deactivation end-capping from a dormant to active state, and (2) a degenerative chain transfer mechanism.…”