Block copolymers with stable radical and fluorinated groups by ATRP
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olymers/Soft Matter Research Letter
Block copolymers with stable radical and fluorinated groups by ATRP Clemens Liedel†, Materials Science and Engineering, 214 Bard Hall, Cornell University, Ithaca, New York 14853 Austin Moehle and Gregory D. Fuchs, Applied and Engineering Physics, 271 Clark Hall, Cornell University, Ithaca, New York 14853 Christopher K. Ober, Materials Science and Engineering, 214 Bard Hall, Cornell University, Ithaca, New York 14853 Address all correspondence to Christopher K. Ober at [email protected] (Received 10 February 2015; accepted 19 June 2015)
Abstract Polymers with stable radical groups are promising materials for organic electronic devices due to their unique redox activity. Block copolymers with one redox active block could be used in nanostructured devices for electronic applications. We report on the synthesis and characterization of such multifunctional block copolymers in which phase separation on the 10 nm (half pitch) scale is achieved by using fluorinated blocks. Fluorination of one block increases the degree of phase separation and leads to smaller accessible domain sizes. Block copolymers with 60%, 80% and 90% of a stable radical containing block and either fluorinated or non-fluorinated second blocks were made by atom transfer radical polymerization, and their microstructure formation as a function of fluorine content is described after solvent vapor or thermal annealing. Electrical characterization of such a partly fluorinated block copolymer shows their potential for electronic devices.
Introduction Almost 50 years ago, Griffith et al. described the synthesis of polymers with stable radical groups (stable radical polymers).[1] Their oxidation or reduction is reversible and proceeds through a fast one-electron transfer reaction, which makes them promising materials as active species in the cathode or anode material of batteries.[2–5] Stable radicals bound to polymer backbones have been reported to increase conductivity and open potential applications in metal-free batteries.[3–5] Polymers made from 2,2,6,6-tetramethyl-1-piperidinyloxy4-yl methacrylate are the most widely investigated of all stable radical polymers. Most of the more recent research on stable radical polymers focuses on polymerization techniques with limited control over molecular weight dispersity.[2,6] Only within the last few years, polymer formation by living anionic[1,7–10] or controlled polymerization techniques of such polymers such as ring-opening metathesis polymerizations,[11,12] reversible addition-fragmentation chain-transfer polymerizations,[13–17] nitroxide mediated polymerizations,[15] or atom transfer radical polymerizations (ATRP)[15,18–24] was reported. A limited number of articles have reported block copolymers with a block that contains stable radical groups,[12,14,16,23] and they only show disordered phase-separated block copolymer structures. Block copolymer phase separation only occurs if the interaction parameter between the blocks, χ, is sufficiently big, the degree of polymerization is high
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