Micellization of block copolymers Block copolymers are mostly referred to in the following by abbreviation of their segments, such as PS–PMMA instead of PS-b-PMMA for poly (styrene)-b-poly(methylmethacrylate)

Micellization of block copolymers

Gérard Riess*

Lab de Chimie Macromoleculaire, Ecole Nationale Supérieure de Chimie de Mulhouse, Institut de Chimie des Surfaces et Interfaces,

3 rue Alfred Werner, 68093 Mulhouse Cedex, France

Received 26 July 2002; revised 15 January 2003; accepted 16 January 2003

Abstract

This article deals with recent progress including the author’s work in the field of block copolymer self-assembly in solution

and on solid surfaces. The synthesis methods for producing block copolymers with well-defined structures, molecular weights

and composition are outlined with emphasis on ionic and controlled free radical polymerization techniques. A general overview

of the preparation, characterization and theories of block copolymer micellar systems is presented. Selected examples of

micelle formation in aqueous and organic medium are given for di- and triblock copolymers, as well as for block copolymers

with more complex architectures. Current and potential application possibilities of block copolymer colloidal assemblies as

stabilizers, flocculants, nanoreservoir in, among others, controlled delivery of bioactive agents, catalysis, latex agglomeration

and stabilization of non-aqueous emulsion are also discussed.

q 2003 Elsevier Science Ltd. All rights reserved.

Keywords: Block copolymers; Synthesis; Micellization; Micelles; Micellar architectures; Comicellization; Colloidal nanostructures; Self-

aggregation; Self-assembly; Controlled drug delivery; Polyion micellar complexes; Metal nanoparticles; Surface modification

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1108

2. Synthesis and structures of block copolymers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1110

2.1. Block copolymers with linear A–B and A–B–A architecture . . . . . . . . . . . . . . . . . . . . . . . . . .1111

2.1.1. Free radical polymerization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1111

2.1.2. Anionic polymerization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1112

2.1.3. Cationic polymerization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1113

2.1.4. Mechanism switching—difunctional initiators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1113

2.1.5. Coupling reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1113

2.1.6. Chemical modification of precursor block copolymers . . . . . . . . . . . . . . . . . . . . . . . . . .1114

2.2. Block copolymers with complex molecular architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1114

2.2.1. Block copolymers with poly A/poly B sequences. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1114

2.2.2. Block copolymers with poly A/poly B/poly C sequences . . . . . . . . . . . . . . . . . . . . . . . .1114

3. Block copolymer micelles: preparation techniques and characteristics . . . . . . . . . . . . . . . . . . . . . . . . .1117

3.1. Micellization of block copolymer—generalities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1117

3.2. Preparation techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1119

0079-6700/03/$ - see front matter q 2003 Elsevier Science Ltd. All rights reserved.

doi:10.1016/S0079-6700(03)00015-7

Prog. Polym. Sci. 28 (2003) 1107–1170

www.elsevier.com/locate/ppolysci

* Tel.: þ33-389-33-68-47; fax: þ33-389-33-68-54. E-mail address: [email protected] (G. Riess).

http://www.elsevier.com/locate/ppolysci

3.3. Characterization of block copolymer micelles—experimental techniques . . . . . . . . . . . . . . . . . .1120

3.3.1. Critical micelle concentration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1120

3.3.2. Morphology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1122

3.3.3. Size, molecular weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1122

3.4. Dynamics of micellar systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1122

3.4.1. Kinetics of micellization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1122

3.4.2. Micelle hybridization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1123

3.4.3. Chain dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1124

3.5. Solubilization in micelles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1124

4. Theories and computer simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1126

4.1. Thermodynamic background. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1126

4.2. Scaling theories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1127

4.3. Mean-field theories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1127

4.4. Computer simulations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1128

5. Micellization in aqueous medium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1129

5.1. Micellization of non-ionic hydrophilic–hydrophobic block copolymers . . . . . . . . . . . . . . . . . . .1129

5.1.1. PEO–poly(oxyalkylene) copolymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1129

5.1.2. PS–PEO copolymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1130

5.1.3. Miscellaneous non-ionic copolymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1131

5.2. Micellization of anionic amphiphilic block copolymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1132

5.3. Micellization of cationic amphiphilic copolymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1133

5.4. Micellization of double hydrophilic block copolymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1135

6. Micellization of block copolymers in organic medium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1136

6.1. Micellization of hydrophobic–hydrophilic block copolymers . . . . . . . . . . . . . . . . . . . . . . . . . . .1137

6.1.1. Micellization in polar non-aqueous solvents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1137

6.1.2. Micellization in non-polar solvents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1137

6.2. Micellization of hydrophobic–hydrophobic block copolymers . . . . . . . . . . . . . . . . . . . . . . . . . .1138

7. Novel micellar architectures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1140

7.1. Micellar architectures derived from linear AB and ABA block copolymers. . . . . . . . . . . . . . . . .1140

7.2. Cross-linked micellar structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1143

7.3. Micellization of AB block copolymers with non-linear architecture . . . . . . . . . . . . . . . . . . . . . .1144

7.4. Micellization of functionalized block copolymers and of ABC triblock copolymers. . . . . . . . . . .1144

7.5. Comicellization and complex formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1147

8. Application possibilities of block copolymer micellar systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1149

8.1. Solubilization of active components in block copolymer micelles: biomedical applications . . . . .1149

8.1.1. Drug loaded micelles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1150

8.1.2. Polyion micellar complexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1151

8.2. Metal nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1152

8.3. Adsorption and surface modification by block copolymer micelles . . . . . . . . . . . . . . . . . . . . . . .1152

8.4. Miscellaneous applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1155

9. Concluding remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1156

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1158

References