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Styrene–vinyl pyridine diblock copolymers: Synthesis by RAFT polymerization and self‐assembly in solution and in the bulk
Authors:Mirela Zamfir  Costas S. Patrickios  Franck Montagne  Clarissa Abetz  Volker Abetz  Liat Oss‐Ronen  Yeshayahu Talmon
Affiliation:1. Department of Chemistry, University of Cyprus, PO Box 20537, 1678 Nicosia, Cyprus;2. Division of Nanotechnology and Life Sciences, Swiss Center for Electronics and Microtechnology SA (CSEM SA), CH 2002 Neuchatel, Switzerland;3. Institute of Polymer Research, Helmholtz‐Zentrum Geesthacht, Max‐Planck‐Str. 1, 21502 Geesthacht, Germany;4. Department of Chemical Engineering, Technion‐Israel Institute of Technology, Haifa 32000, Israel
Abstract:Reversible addition‐fragmentation chain transfer (RAFT) polymerization along with benzyl dithiobenzoate chain transfer agent was employed for the controlled preparation of four diblock copolymers of styrene (St, less polar monomer) and 2‐ or 4‐vinyl pyridine (2VP or 4VP, more polar monomers): St161b‐2VP48, St161b‐2VP121, St161b‐4VP76, and St161b‐4VP107, where the subscripts indicate the experimentally determined degrees of polymerization for each block. These diblock copolymers and their common St homopolymer precursor were characterized in terms of their molecular weights and compositions using gel permeation chromatography and 1H NMR spectroscopy, respectively. All four diblock copolymers self‐assembled in dilute toluene solutions to form reverse spherical micelles, which were characterized using atomic force microscopy and cryogenic transmission electron microscopy. Both microscopy techniques revealed that the 4VP‐bearing diblock copolymers formed larger micelles than the 2VP‐bearing ones, a result of the greater 4VP‐toluene incompatibility as compared to the 2VP‐toluene one. Finally, films cast from chloroform solutions of the diblocks were investigated in terms of their bulk morphologies using transmission electron microscopy. While the 2VP‐containing block copolymer self‐assembled into a spherical morphology, the 4VP‐containing one with comparable composition and molecular weight formed a cylindrical structure, manifesting the greater 4VP‐St incompatibility as compared to that of the 2VP‐St pair. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Keywords:bulk morphologies  diblock copolymers  living radical polymerization  micelles  reversible addition‐fragmentation chain transfer polymerization  self‐assembly  self‐organization  styrene  2‐vinyl pyridine  4‐vinyl pyridine
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