recent_advances_in_ABC_block_copolymers

recent_advances_in_ABC_block_copolymers - Recent Advances...

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Recent Advances in ABC Triblock Copolymers Danyell S. Wilson November 25, 2003 University of Florida Key words: ABC triblock Copolymers, living anionic polymerization (LAP), atom transfer radical polymerization (ATRP), semicrystalline, graft copolymers, block copolymers, micelles, nanotechnology Abstract: This review covers the current status of ABC Triblock copolymers synthesized using living anionic polymerization or atom transfer radical polymerization and assesses recent advances made in the last five years. Block copolymers are material systems in which a chain of N A units of monomer A is covalently linked to a chain of N B units of monomer B. Living anionic polymerization for synthesizes of block copolymers is oe of the oldest synthesis techniques conducted in the absence of undesired transfer agents and does not undergo termination. Atom transfer radical polymerization technique involves a redox process where the initiator is reduced by transition metal complex, which forms a radical initiating species leaving a metal halide complex. Recent publications (1999 to present) will be discussed on how these brilliant self-assembly materials are of great importance growing field of nanotechnology due to their periodic microphase-separated composite structures 2 and crystallization properties. 1
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A billion dollar market annually, 1 block copolymers dominate the research field of macromolecular chemistry and physics. Theoreticians and experimentalists both express interest in the numerous morphologies (lamellae, gyroid, and cylinder) and controlled synthesis techniques of block copolymers. Nearly fifty years ago, living anionic polymerization (LAP) governed the synthesizing technique available; now methods vary from atom transfer radical polymerization (ATRP), ring opening metathesis polymerization (ROMP), to reversible addition fragmentation chain transfer (RAFT). This review focuses on LAP synthesis of semicrystalline ABC triblock copolymers and ATRP production of graft ABC triblock copolymers. In addition, recent publications (1999 to present) will be discussed on how these brilliant self-assembly materials are of great importance growing field of nanotechnology due to their periodic microphase- separated composite structures 2 and crystallization properties. Block copolymers are material systems in which a chain of N A units of monomer A is covalently linked to a chain of N B units of monomer B. For example, as seen in scheme 1, an AB diblock copolymer, styrene-b-methyl methacrylate diblock , is produced by polymerization of monomer A to completion using a common ionic initiator, butyllithium, then monomer B is add to the stable carbanion end chain beginning propagation. This process is known as living anionic polymerization, which can be conducted in the absence of undesired transfer agents 1 and does not undergo termination; H 2 O is added to isolate the polymer. (See Scheme 2) First attempts to polymerize triblock copolymers using styrene and isoprene were with a difunctional initiator were
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recent_advances_in_ABC_block_copolymers - Recent Advances...

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