Block_copolymer_theory_experiment_Annu. Rev.Phys.Chem._41_525-57_Bates(1990)

Block_copolymer_theory_experiment_Annu. Rev.Phys.Chem._41_525-57_Bates(1990)

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Annu. Rev. Phys. Chem. 1990. 41:525-57 Copyright 1990 by Annual Reviews Inc. All rights reserved BLOCK COPOLYMER THERMODYNAMICS: Theory and Experiment Frank S. Bates Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455 Glenn H. Fredrickson ~ AT&T Bell Laboratories, Murray Hill, New Jersey 07974 KEY WORDS: order and disorder. INTRODUCTION Block copolymers are macromolecules composed of sequences, or blocks, of chemically distinct repeat units. The development of this field originated with the discovery of termination-free anionic polymerization, which made possible the sequential addition of monomers to various carbanion-ter- minated ("living") linear polymer chains. Polymerization of just two dis- tinct monomer types (e.g. styrene and isoprene) leads to a class of materials referred to as AB block copolymers. Within this class, a variety of molec- ular architectures is possible. For example, the simplest combination, obtained by the two-step anionic polymerization of A and B monomers, is an (A-B) dioblock copolymer. A three-step reaction provides for the preparation of(ABA) or (BAB) triblock copolymer. Alternatively, "living" diblock copolymers can be reacted with an n-functional coupling agent to produce (AB)n star-block copolymers, where n = 2 constitutes a triblock copolymer. Several representative (A-B)n block copolymer architectures ~ Present address: Department of Chemical and Nuclear Engineering, University of Cali- fornia, Santa Barbara, California 93106. 525 0066-426X/90/11014)525502.00 www.annualreviews.org/aronline Annual Reviews Annu. Rev. Phys. Chem. 1990.41:525-557. Downloaded from arjournals.annualreviews.org by UNIVERSITY OF FLORIDA on 01/14/08. For personal use only. 526 BATES & FREDRICKSON are illustrated in Figure 1. As a consequence of the "living" nature of these reactions, the resulting block and overall molecular weight distributions are nearly ideal, i.e. Mw/Mr~ < 1.1, where Mw and MN represent the weight and number-average molecular weights, respectively. Since the original studies of anionic block copolymerization in the 1950s (1, 2) a variety of new polymerization mcthods (e.g. condensation, Ziegler- Natta, etc.) have contributed to an expanding number of block copolymer classes (e.g. ABC) and novel architectures (e.g. graft-block). Although some of the developments have resulted in important new materials (e.g. polyurethanes), anionic polymerization remains the only viable method for (A-B)n Block Copolymer Architectures k.. J,~ triblock Figure 1 Schematic illustration of several (A-B), type block copolymer architectures. Solid and dashed lines represent A and B block chains. The n = 1 and n = 2 architectures are commonly referred to as diblock and triblock copolymers, while n __ 3 are denoted starblock copolymers....
View Full Document

This note was uploaded on 07/20/2011 for the course EMA 6165 taught by Professor Brennan during the Spring '08 term at University of Florida.

Page1 / 35

Block_copolymer_theory_experiment_Annu. Rev.Phys.Chem._41_525-57_Bates(1990)

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online