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Rigid Polymer Networks: Advances in Polymer Science Volume 118

Table of Contents

List of Symbols

1 Introduction

General Classification of Liquid-Crystal Polymers

and Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1.2.1 Definition of Liquid-Crystal Polymers . . . . . . . . . . . . . . 8

1.2.2 Flexible Chain Polymers with Mesogenic Groups . . . . . . . 10

1.2.3 Networks with Flexible Chains and Stiff Mesogenic

Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1.2.3.1 Networks with Stiff Main-Chain Mesogens,

Flexible Spacers and Flexible Junctions . . . . . . . . . 13

1.2.3.2 Networks with Stiff Main-Chain Mesogens,

Flexible spacers and Rigid Branchpoints . . . . . . . . 16

1.2.3.3 Networks with Stiff Pendant Mesogens, Flexible

Main-Chains and Flexible Junctions . . . . . . . . . . 18

1.2.3.4 Networks with Stiff Pendant Mesogens Connected

at Both Ends to Flexible Main Chains . . . . . . . . . 21

1.2.4 Networks Containing No Flexible Spacers . . . . . . . . . . . 25

1.2.4.1 Uniform Main-Chain Mesogenicity: Flexible,

Wormlike, Rodlike . . . . . . . . . . . . . . . . . . . . . 26

1.2.4.2 LCPs from Biological Origin and

Their Networks . . . . . . . . . . . . . . . . . . . . . . . 33

1.2.4.3 Networks with Uniform Main-Chain

Mesogeni-city and Flexible Crosslinking Residues . . 34

1.3 The Fractal Character of Pre-Gel and Post-Gel

Highly Branched Polymers . . . . . . . . . . . . . . . . . . . . . . . . 38

Exclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Synthetic Highlights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

3.1 One-Step and End-Capped Rigid Networks . . . . . . . . . . . . . . 46

3.1. t Networks with Stiff Hydrocarbon Segments . . . . . . . . . . 46

3.1.1.1 Polyphenylenes and Poly (Substituted Phenylenes).. 46

3.1.1.2 Hydrocarbon Networks with Very Short Aromatic

Segments . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

3.1.1.3 Stiff Aliphatic Segments . . . . . . . . . . . . . . . . . . 52

3.1.1.4 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

3.1.2 Aromatic Polyamide Networks with Stiff Segments

and Rigid Branchpoints . . . . . . . . . . . . . . . . . . . . . . 54

3.1.2.1 Rigid Polyamide Networks, Gels and Fractal

Polymers Prepared in Solution in the Presence

of Triarylphosphite . . . . . . . . . . . . . . . . . . . . . 54

3.1.2.2 Rigid Polyamide Networks and Fractal Polymers

Prepared in Solution by Other Procedures . . . . . . . 66

3.1.3 Rigid Aromatic Polyester Networks . . . . . . . . . . . . . . . 68

3,1.4 Rigid Aromatic Networks Containing Single-Atom Bridges . 70

3.1.4.1 Aromatic Hydrocarbons with Methylene Bridges... 72

3.1.4.2 Phenol-Formaldehyde Type Networks . . . . . . . . . 73

3.1.4.3 Furan-Containing Networks . . . . . . . . . . . . . . . 76

3.1.4.4 Aromatic Polyether and Ether-Containing

Networks . . . . . . . . . . . . . . . . . . . . . . . . . . 78

3.1.4.5 Bridged Aromatic Networks with Uncommon

Electronic Structure . . . . . . . . . . . . . . . . . . . . 80

3.1.4.6 Morphology and Possible Fractality . . . . . . . . . . 84

3.1.5 Rigid Networks with Triazine Branchpoints . . . . . . . . . . 85

3.1.6 Rigid Networks from Stiff End-Capped Segments . . . . . . . 92

3.t.6.1 Networks with Unsaturated Imide Junction

Precursors . . . . . . . . . . . . . . . . . . . . . . . . . . 93

3.1.6.2 Networks Crosslinked by Strained-Ring Precursors . 96

3.1.6.3 Networks Crosslinked by Ethynyl End-Caps

and Pendant Groups . . . . . . . . . . . . . . . . . . . 102

3.2 Two-Step Aromatic Networks . . . . . . . . . . . . . . . . . . . . . 107

3.2.1 Two-Step Aromatic Polyamide Networks . . . . . . . . . . . 108

3.2.2. Two-Step Networks from Poly (Ether Ketone Ketone)

(PEKK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

3.2.3 Networks from Aromatic Linear Chains Created

by Reacting Backbone Diacetylene or Pendant

Acetylene Groups . . . . . . . . . . . . . . . . . . . . . . . . . 113

32.4 Potential Two-Step Polyarylene Networks . . . . . . . . . . 116

3.2.5 Supernetworks . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

4.1 Pre-Gel State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

4.1.1 Fractal Nature of Growing One-Step Species

and Comparison with Two-Step Species . . . . . . . . . . . . 121

4.1.2 Co*, the Critical Concentration for Gelation . . . . . . . . . 135

4.2 Post-Gel State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142

4.2.1 Fractal Nature of Gelled Rigid Networks . . . . . . . . . . . 142

4.2.2 Manifestations of Rigid Network Defects . . . . . . . . . . . 149

4.2.3 Mechanical Properties of Rigid Networks and Their Gels . 152

4.2.4 Observations on Effects of Gravity and Flow-Stress During

the Formation of Rigid Network Gels . . . . . . . . . . . . . 155

4.2.5 High Temperature Stability of Rigid Aromatic Networks.. 157

4.3 Some Properties of Liquid-Crystal Polymer Networks . . . . . . . 159

4.4 Modes of Segmental Deformation . . . . . . . . . . . . . . . . . . . 161

4.4.1 Description of Segments . . . . . . . . . . . . . . . . . . . . . 161

4.4.1.1 Mathematical Description of the Molecules . . . . . 161

4.4.1.2 General Empirical Description of Network

Segments . . . . . . . . . . . . . . . . . . . . . . . . . . 164

4.4.2 Deformation of Aromatic Segments with Bridges

Consisting Exclusively of Coaxial Single Bonds . . . . . . . 166

4.4.3 Deformation of Stiff Aromatic Segments with Bridges

Consisting of a Single Non-Coaxial Bond Connecting

Two Coaxial Bonds Between Aromatic Groups . . . . . . . 168

4.4.4 Deformation of Aromatic Segments with Swivels

Consisting of Two Single Bonds

Connected by a Single Atom . . . . . . . . . . . . . . . . . . 175

4.4.5 Deformation of Networks with Stiff Aromatic Segments

and Relatively Flexible Aliphatic Junctions Created

from Reactive End-Caps . . . . . . . . . . . . . . . . . . . . . 177

4.5 Questions of Elastic Constants . . . . . . . . . . . . . . . . . . . . 179

5. Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192

5.1. The Problem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

5.1.1 Responses of Flexible and Rigid Networks to Stress

Fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

5.1.2 Complexities Uniquely Linked to Network Rigidity . . . . 193

5.2 Theoretical Description of Rigid Networks . . . . . . . . . . . . . 194

5.2.1 One-Step Networks . . . . . . . . . . . . . . . . . . . . . . . 194

5.2.1.1 General Mathematical Description . . . . . . . . . . 200

5.2.1.2 Field Formalism for Deformation . . . . . . . . . . 203

5.3 Simpler Theoretical Approaches . . . . . . . . . . . . . . . . . . . 206

5.3.1 Simple Calculations of the Concentrated Rigid Network . 206

5.3.2 Simple Calculations in a Dilute Rigid Network . . . . . . . 208

6 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214

Author Index Volumes 101-118 . . . . . . . . . . . . . . . . . . . . . . . . . 233

Subject Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

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