Photo-Sensitive RAFT-Agents for Advanced Microparticle Design

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• 作者：Michael Kaupp ; Thomas Tischer ; Astrid F. Hirschbiel ; Andrew P. Vogt ; Udo Geckle ; Vanessa Trouillet ; Thorsten Hofe ; Martina H. Stenzel ; Christopher Barner-Kowollik
• 刊名：Macromolecules
• 出版年：2013
• 出版时间：September 10, 2013
• 年：2013
• 卷：46
• 期：17
• 页码：6858-6872
• 全文大小：819K
• 年卷期：v.46,no.17(September 10, 2013)
• ISSN：1520-5835

文摘

The current contribution describes the combination of an efficient reversible deactivation radical polymerization process (reversible addition鈥揻ragmentation chain transfer (RAFT) polymerization) with a mild light-induced modular ligation technique. A novel RAFT-agent was synthesized which carries a photoactive group based on ortho-quinodimethane (photo-enol) chemistry. The novel photoreactive RAFT-agent controls the polymerization of a wide range of monomers such as styrene, N,N-dimethylacrylamide and a protected glycomonomer (2-(2鈥?3鈥?4鈥?6鈥?tetra-O-acetyl-尾-d-mannosyloxy)ethyl acrylate) with dispersities between 1.07 and 1.17 (3500 g路mol^鈥? 鈮?M_n 鈮?10100 g路mol^鈥?) and quantitative end-group functionalization. The photo-enol group reacts with dieneophiles under mild irradiation (位_max = 320 nm) at ambient conditions 鈥?so that the RAFT-group remains intact 鈥?and without any catalyst to form block copolymers in a matter of minutes. Furthermore, the RAFT-polymers can be photografted onto porous polymeric (poly(glycidyl methacrylate)) microspheres, after a one-step prefunctionalization with maleimide moieties. The successful photografting is evidenced by scanning electron microscopy (SEM), elemental analysis (EA), X-ray photoelectron spectroscopy (XPS) and high resolution attenuated total reflectance (ATR) FT-IR microscopy, which leads to qualitative as well as quantitative grafting data. The grafting densities obtained for polystyrene are close to 0.11 chains per nm² (M_n = 3900 g路mol^鈥?) and for poly(N,N-dimethylacrylamide) close to 0.12 chains per nm² (M_n = 3500 g路mol^鈥?). To highlight the additional benefit of employing a light-induced grafting reaction, Janus microspheres were prepared with poly(N,N-dimethylacrylamide) employing a Pickering emulsion approach and illustrated via ATR-FT-IR microscopy.