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Diblock Copolymers

The unlike blocks in block copolymers tend to phase separate into microdomains forming different mesophases. The size scale of the domains is governed by the chain dimensions and the block ratio determines the mesophase structure.

The known equilibrium mesophases for diblock copolymers (spheres (S), cylinders (C), gyroid (G), and lamellae (L)) are shown in the phase diagram at right.

BC theoretical phase diagram
AB Phases

Our group is involved in the synthesis and characterization of functional polymers, with different molecular architectures. Fundamental studies on AB block copolymer thermodynamics rely on the preparation of monodispersed materials with well-defined molecular weights (MWs) and block volume fractions ( f ). This is typically accomplished through a living polymerization technique by sequential monomer addition.

The most widely used technique for the preparation of model block copolymers is living anionic polymerization. The active centers in anionic polymerizations are highly reactive carbanions. Some typical polymers made by anionic polymerization are polystyrene, poly(ethylene oxide) and block copolymers like poly(styrene- block -isoprene), PS- b -PI and poly(isoprene-block-ethylene oxide), PI- b -PEO. The diblock copolymers are used for the synthesis of organic/inorganic hybrid materials.

All images and text Copyright 2008

Wiesner Research Group - Cornell University

References:

S. Mahajan, S. Renker, P. Simon, J. Gutmann, A. Jain, S. Gruner, L. Fetters, G. Coates, U. Wiesner, "Synthesis and characterization of amphiphilic poly(ethylene oxide)-block-poly(hexyl methacrylate) copolymers" Macromolecular Chemistry and Physics, 204(8), 2003, 1047-1055.

P. Gopalan, Y. Zhang, X. Li, U. Wiesner, C. K. Ober, Liquid Crystalline Rod-Coil Block Copolymers by Stable Free Radical Polymerization: Synthesis, morphology, and rheology, Macromolecules 36, 2003, 3357-3364

M. Schöps, H. Leist, A. DuChesne, U. Wiesner, Salt-Induced Switching of Microdomain Morphology of Ionically Functionalized Diblock Copolymers, Macromolecules 32, 1999, 2806-2809

V.Schädler, J. Spickermann, H.-J. Räder, U. Wiesner, Synthesis and Characterization of a,w-Zwitterionic Block copolymers of Styrene and Isoprene, Macromolecules 29, 1996, 4865-4870