Inorganic Polymers, Second Edition
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Inorganic Polymers, Second Edition James E. Mark Harry R. Allcock Robert West OXFORD UNIVERSITY PRESS INORGANIC POLYMERS This page intentionally left blank INORGANIC POLYMERS Second Edition James E. Mark Harry R. Allcock Robert West 1 2005 3 Oxford University Press, Inc., publishes works that further Oxford University’s objective of excellence in research, scholarship, and education. Oxford New York Auckland Cape Town Dar es Salaam Hong Kong Karachi Kuala Lumpur Madrid Melbourne Mexico City Nairobi New Delhi Shanghai Taipei Toronto With offices in Argentina Austria Brazil Chile Czech Republic France Greece Guatemala Hungary Italy Japan Poland Portugal Singapore South Korea Switzerland Thailand Turkey Ukraine Vietnam Copyright © 2005 by Oxford University Press, Inc. Published by Oxford University Press, Inc. 198 Madison Avenue, New York, New York, 10016 www.oup.com This volume is a revised edition of Inorganic Polymers published in 1992 by Prentice Hall. Oxford is a registered trademark of Oxford University Press All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of Oxford University Press. Library of Congress Cataloging-in-Publication Data Mark, James E., 1934– Inorganic polymers/James E. Mark, Harry R. Allcock, Robert West.—2nd ed. p. cm. Includes bibliographical references and index. ISBN-13 978-0-19-513119-2 ISBN-0-19-513119-3 1. Inorganic polymers. I. Allcock, H. R. II. West, Robert, 1928– III. Title. QD196.M37 2004 546—dc22 2004043395 987654321 Printed in the United States of America on acid-free paper Preface to the Second Edition As was the case with the first edition, the goal was to provide a broad overview of inorganic polymers in a way that will be useful to both the uninitiated and to those already working in this field. The coverage has been updated and expanded significantly to cover advances and interesting trends since the first edition appeared. The most obvious changes are the three new chapters, “Ferrocene-Based Polymers, and Additional Phosphorus- and Boron-Containing Polymers,” “Inorganic-Organic Hybrid Composites,” and “Preceramic Inorganic Polymers.” The authors once again hope that readers will be inspired to enter and contribute to this fascinating area of inorganic polymeric materials. This page intentionally left blank Preface to the First Edition Most polymers being synthesized, characterized, and utilized in today’s world are organic in nature. That is, their chain backbones consist primarily of carbon atoms, frequently along with some heteroatoms such as oxygen and nitrogen. Their attractive properties, such as easy processibility, high strength, and low density, have been exploited in all industrialized societies to the extent that it is now difficult to imagine life without them. In spite of their many successes, organic polymers have a number of deficiencies. For one, the monomers from which they are prepared are frequently subject to the vagaries of the petroleum industry. The polymers themselves frequently have low soft- ening temperatures or low degradation temperatures. Many are also vulnerable to degradation from oxygen, ozone, or high-energy radiation. Some are subject to disso- lution or swelling when in contact with solvents or fluids in commercial applications. Finally, many present environmental problems by resisting incorporation into the biosphere, or by forming highly toxic products upon combustion. Inorganic polymers, with backbones typically of silicon, phosphorus, oxygen, or nitrogen atoms, are now being more and more intensively studied. One obvious reason is the quest to find materials not suffering from some of the limitations mentioned above. No single polymer, of course, can be expected to meet all of the desired proper- ties for an application, particularly in the high-technology area. Nonetheless, the very different chemical nature of inorganic materials suggests they could well be superior to their organic counterparts in a variety of ways. The polysiloxanes, with their superb thermal stability, are a good example in this regard. The controlled degradability and the innocuous degradation products of polyphosphazenes in controlled drug-delivery systems is another. There are numerous other reasons for being interested in inorganic polymers. One is the simple need to know how structure affects the properties of a polymer, particularly viii PREFACE TO THE FIRST EDITION outside the well-plowed area of organic materials. Another is the bridge that inorganic polymers provide between polymer science and ceramics. More and more chemistry is being used in the preparation of ceramics of carefully controlled structure, and inor- ganic polymers are increasingly important precursor materials in such approaches. The present book was prepared to provide an introduction to the field of inorganic polymers. There has long been a need for such a book, as opposed to the ready avail- ability of numerous other books, that are highly specialized and written for scientists already working in this area. The only background required for its comprehension are the basic concepts presented in a typical undergraduate course in chemistry. Some famil- iarty with the fundamentals of polymer science would be helpful, but not necessary, since many of these are covered in an introductory chapter on polymer characterization. It is hoped that the book will be useful to a variety of readers, including polymer chemists, inorganic chemists, chemical engineers, and materials scientists. The highly tutorial nature of the presentation should also make it useful as a textbook, for a one- term course. One of the advantages of writing a book is the uncovering of an almost endless series of interesting research ideas. We hope our readers benefit in the same way and will explore more deeply this fascinating new area of polymer science and engineering. Contents About the Authors xiii 1 Introduction 3 1.1 What Is a Polymer? 3 1.2 How Polymers Are Depicted 3 1.3 Reasons for Interest in Inorganic Polymers 5 1.4 Types of Inorganic Polymers 6 1.5 Special Characteristics of Polymers 7 2 Characterization of Inorganic Polymers 8 2.1 Molecular Weights 8 2.2 Molecular Weight Distributions 18 2.3 Other Structural Features 22 2.4 Chain Statistics 26 2.5 Solubility Considerations 28 2.6 Crystallinity 34 2.7 Transitions 40 2.8 Spectroscopy 49 2.9 Mechanical Properties 50 References 58 3 Polyphosphazenes 62 3.1 Introduction 62 3.2 History 65 3.3 Alternative Synthesis Routes to Linear Polymers 70 3.4 Surface Reactions of Polyphosphazenes 83 x CONTENTS 3.5 Hybrid Systems through Block, Comb, or Ring-Linked Copolymers 84 3.6 Hybrid Systems through Composites 93 3.7 Organometallic Polyphosphazenes 93 3.8 Small-Molecule Models 99 3.9 Molecular Structure of Linear Polyphosphazenes 100 3.10 Structure–Property Relationships 107 3.11 Applications of Polyphosphazenes 111 3.12 Optical and Photonic Polymers 137 3.13 Polymers Related to Polyphosphazenes 141 3.14 Conclusions 143 References 146 4 Polysiloxanes and Related Polymers 154 4.1 Introduction 154 4.2 History 155 4.3 Nomenclature 155 4.4 Preparation and Analysis 156 4.5 General Properties 162 4.6 Reactive Homopolymers 176 4.7 Elastomeric Networks 177 4.8 Some New Characterization Techniques Useful for Polysiloxanes 181 4.9 Copolymers and Interpenetrating Networks 183 4.10 Applications 184 References 189 5 Polysilanes and Related Polymers 200 5.1 Introduction 200 5.2 History 201 5.3 Synthesis 204 5.4 Chemical Modification of Polysilanes 212 5.5 Physical Properties of Polysilanes 213 5.6 Electronic Properties of Polysilanes 215 5.7 Chromotropism of Polysilanes 220 5.8 Electrical Conductivity and Photoconductivity 230 5.9 Luminescence of Polysilanes 232 5.10 Photodegradation of Polysilanes 233 5.11 Cross-Linking 234 5.12 Structural Arrangements in Polysilanes 236 5.13 Technology of Polysilanes 244 5.14 Additional Readings 250 References 250 CONTENTS xi 6 Ferrocene-Based Polymers, and Additional Phosphorus- and Boron-Containing Polymers 254 6.1 Ferrocene-Based Polymers 254 6.2 Other Phosphorus-Containing Polymers 266 6.3 Boron-Containing Polymers 269 References 270 7 Miscellaneous Inorganic Polymers 273 7.1 Introduction 273 7.2 Other Silicon-Containing Polymers 273 7.3 Polygermanes 275 7.4 Polymeric Sulfur and Selenium 276 7.5 Other Sulfur-Containing Polymers 279 7.6 Aluminum-Containing Polymers 284 7.7 Tin-Containing Polymers 284 7.8 Arsenic-Containing Polymers 286 7.9 Metal Coordination Polymers 286 7.10 Other Organometallic Species for Sol-Gel Processes 289 References 290 8 Inorganic-Organic Hybrid Composites 294 8.1 Sol-Gel Ceramics 294 8.2 Fillers in Elastomers 295 8.3 Polymer-Modified Ceramics 305 References 307 9 Preceramic Inorganic Polymers 312 9.1 Overview of Ceramic Aspects 312 9.2 The Sol-Gel Process to Oxide Ceramics 313 9.3 Carbon Fiber 319 9.4 Silicon Carbide (SiC) 320 9.5 Silicon Nitride (Si3N4) 324 9.6 Boron Nitride (BN) 327 9.7 Boron Carbide (B4C) 329 9.8 Aluminum Nitride (AlN) 330 9.9 Phosphorus Nitride (P3N5) 330 9.10 Poly(ferrocenylsilanes) as Ceramic Precursors 331 References 332 Index 335 This page intentionally left blank About the Authors James E. Mark received his B.S. degree in 1957 in Chemistry from Wilkes College and his Ph.D. degree in 1962 in Physical Chemistry from the University of Pennsylvania. After serving as a Postdoctoral Fellow at Stanford University under Professor Paul J. Flory, he was Assistant Professor of Chemistry at the Polytechnic Institute of Brooklyn before moving to the University of Michigan, where he became a Full Professor in 1972. In 1977, he assumed the position of Professor of Chemistry at the University of Cincinnati, and served as Chairman of the Physical Chemistry Division and Director of the Polymer Research Center. In 1987, he was named the first Distinguished Research Professor, a position he holds at the present time.