An Introduction to Macromolecules PDF
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HEIDELBERG SCIENCE LIBRARY Leo Mandelkern An Introduction to Macromolecules Second Edition [SI Springer-Verlag New York Berlin Heidelberg Tokyo Leo Mandelkern Professor of Olemistry The Florida State University Tallahassee, Florida 32306, U.S.A. Library of Congress Cataloging in Publication Data Mandelkern, Leo. An introduction to macromolecules. (Heidelberg science library) Bibliography: p. 156 Includes index. 1. Macromolecules. I. Title. II. Series. QD381.M37 1983 547.7 83-387 © 1972,1983 by Springer-Verlag New York Inc. All rights reserved. No part of this book may be translated or reproduced in any form without written permission from Springer-Verlag, 175 Fifth Avenue, New York, New York 10010, U.S.A. The use of general descriptive names, trade names, trademarks, etc., in this publication, even if the former are not especially identified, is not to be taken as a sign that such names, as understood by the Trade Marks and Merchandise Marks Act, may accordingly be used freely by anyone. Typeset by Publishers Service, Bozeman, Montana. Printed and bound by Halliday Lithograph, West Hanover, Massachusetts. 9 8 7 6 5 432 1 ISBN- 13: 978-0-387-90796-3 e-ISBN-13: 978-1-4612-5494-2 DOl: 1007/978-1-4612-5494-2 To Berdie and Our Three Sons PREFACE TO THE SECOND EDITION The reception of the original volume by students, pedagogues, and reviewers has been most gratifying. It appears to have both satisfied a need and served a useful educational purpose. Hence, some ten years later it has been deemed advisable to bring it up to date, if only in a slightly expanded form. The purpose for writing this book and its level remain the same. Many new polymers have been synthesized in the last decade that have found meaningful and novel uses. Examples of these applications are included in this new edition. Major advances have also been made in biophysics and in molecular biology, as well as in our understanding of natural processes on a molecular level. Foremost among these has been the development of recombinant DNA technology. With it has come the potential for large scale synthesis of hormones and proteins. These new developments have also been incorporated into the present volume. It is my hope that this new edition will still have a widespread appeal to students in all of the natural sciences whatever their major interest. It should also be of use and inter est to those starting industrial or academic careers who have not had an extensive background in macromolecular science. Tallahassee, Florida Leo Mandelkern August, 1982 PREFACE TO THE FIRST EDITION The purpose of this volume is to provide beginning students in the natural sciences with a very elementary introduction to the structure and properties of macromolecular substances. Most students, either those who are science majors or those in a liberal arts program, do not usually have the opportunity to learn about this important class of molecules until they take advanced courses at a senior or graduate level. There is thus a serious gap in our educational processes which has become acute with the widespread recognition of the important role played by macromolecules in biological systems, their extensive use in a myriad of articles of commerce, and their intrinsic scientific interest. We have attempted to rectify this deficiency by presenting a detailed, but non mathematical, description of all classes of macromolecules. Macromolecules are a unique class of substances in that they are molecules of extremely high molecular weight. When certain common structural features are recognized among the different kinds of macromolecules, they can be treated and analyzed from a unified point of view. With this approach, we can discuss in one volume macromolecules of biological interest as well as synthetic materials such as rubbers, glasses, coatings, and fibers. It is our hope that this volume will appeal to students in introductory chemistry, biology, and physics courses and will open to them new vistas and horizons that they would not otherwise experience. It is important to emphasize that it is not intended to serve as an introduction to research in this field. If, however, we succeed in stimulating some readers to pursue further study in this area, we shall be extremely gratified and our efforts will have been well rewarded. The generous assistance and advice from two colleagues is gratefully acknowl edged. Professor G. R. Choppin read a portion of the manuscript in draft form and contributed some very expert advice as to the level and content. Professor K. B. Hoffman was kind enough to read the entire manuscript. Her suggestions and criti cisms were invaluable. Without them it is doubtful whether the manuscript would have been completed. Finally, it is a pleasure to acknowledge Mrs. Suzanne Knuth and Mrs. Sandra Burkholder, who typed the manuscript and prepared it in final form. The author is indebted to them for their labors and for the skills that they brought to the task. Tallahassee, Florida Leo Mandelkern February, 1972 TABLE OF CONTENTS Preface to the Second Edition Preface to the First Edition 1. Introduction 2. Structural Features and Preparation 4 Classification and Definition 4 Chemical Repeating Units 8 Copolymers 17 Preparation 19 Branching, Cross-Linking, and Network Formation 24 3. Chain Structure 28 Internal Rotation 28 Disordered Chain Conformation 34 Ordered Conformations 40 4. Rubbers and Glasses 54 Rubbers-Introduction 54 Structural Basis for Rubber Elasticity 57 Glass Formation 61 Chemical Structure and Glass Formation 65 Plasticizers 66 S. Crystalline Polymers and Fibers 68 Crystal Structures 68 Crystallization Process 70 Undeformed Crystallization-Morphology and Properties 75 Melting Process-Undeformed Crystallization 82 Fibers 88 Mechanochemistry 94 6. Macromolecules of Biological Importance 100 Introduction 100 Polypeptides 100 Conformational Properties of Polypeptides 104 Proteins-General 109 Fibrous Proteins 113 Globular Proteins 121 Nucleic Acids-General 130 Deoxyribonucleic Acid-DNA 134 Ribonucleic Acids-RNA 143 Epilogue: Macromolecules and Man 153 Annotated Bibliography 156 Index 157 An Introduction to Macromolecules Chapter 1 INTRODUCTION The history of mankind has been divided into a number of eras on the basis of the material common to the age. Thus, we have passed through the stone, copper, bronze, and iron ages. The modern epoch may very well be looked back on by his torians as the Age of Macromolecules. Macromolecules, which are also known as polymers, provide both the necessities and amenities of life. Some macromolecules are found in nature in the form of wood, hide, wool, cotton, silk, and rubber. Others are synthetic, or man-made, and are used in our everyday life in the form of plastics, fibers, rubbers, packaging material, the paper upon which we write, paints, and coatings. Macromolecules such as carbohydrates, proteins, and nucleic acids are fundamental to the biological sustenance of life and are indeed the essence of life itself. Natural occurring polymers have of course been in use for a very long time. It is only recently, however, that we have begun to understand the molecular struc ture of these materials and the relationship that exists between their structure, properties, and function. With this new understanding we have been able to use the natural polymers more effectively and have also been able to devise synthetic materials to replace them. Natural occurring systems can be reproduced and we can now even create new macromolecules with properties or combinations of properties that are not paral leled in nature. Thus, we are living in an age in which new materials are constantly replacing older ones. The potential and future benefit to mankind of this under taking appears to be unlimited. We are entering an era where the concern for our resources and recognition of their limited abundance are of paramount concern. The development of appropriate substitutes for scarce resources is a matter of major importance to the national interest and to the welfare of society. Polymeric sub stances will undoubtedly playa significant role in the endeavor to develop replace ment materials. A macromolecule (or "giant molecule" or polymer) is a chemical species of very high molecular weight. For example, water, H 0, a very common low molecular 2 weight substance, has a molecular weight of 18. This means that 1 mole of water, 6.02 X 1023 molecules, will weigh 18 grams. Benzene, a common organic solvent which is another low molecular weight substance, has a molecular weight of 78. However, 1 molecule of natural rubber has a molecular weight of about 1 million, i.e., 106. One mole of rubber will therefore weigh 106 grams, which is more than 1 ton. This comparison gives us a vivid picture of the difference between polymers and substances of low molecular weight. The word "polymer" comes from the Greek and means many parts. The high molecular weight of a polymer is a result of joining together in long chains, by means of chemical bonds, many thousands of atoms. The same types of covalent chemical bonds that are involved in the simpler low molecular weight organic molecules hold these giant molecules together. The kinds of atoms and their geometric arrangement give each macromolecule its chemical distinctiveness and thus its particular use and function.
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