Polymer Microscopy

Third Edition

Polymer Microscopy

Third Edition

Linda C. Sawyer

David T. Grubb

Gregory F. Meyers

~ Springer

Linda C. SawyerCelanese Americas, ret.Palmyra, VA, USA

Gregory F. MeyersAnalytical SciencesDow Chemical CompanyMidland, MI, USA

David T. GrubbProfessorDepartment of Materials Science and EngineeringCornell UniversityIthaca, NY, USA

ISBN: 978-0-387-72627-4 e-ISBN: 978-0-387-72628-1DOl: 10.1007/978-0-387-72628-1

Library of Congress Control Number: 2007928814

© 1987, 1996, 2008 Linda C. Sawyer, David T. GrubbAll rights reserved. This work may not be translated or copied in whole or in part without the written permis­sion of the publisher (Springer Science+Business Media, LLC, 233 Spring Street, New York, NY 10013, USA),except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form ofinformation storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar meth­odology now known or hereafter developed is forbidden.The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are notidentified as such, is not to be taken as an expression of opinion as to whether or not they are subject to pro­prietary rights.

Printed on acid-free paper

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Preface to the Third Edition

The major objective of this text is to provide information on the microscopy techniquesand specimen preparation methods applicable to polymers. The aim is to provide enoughdetail for the methods described to be applied by the reader, while providing appropriatereferences for those who need more detail than can be provided in a single text.

We recognize that scientists from a wide range of backgrounds may be interested inpolymer microscopy. Some may be experienced in the field, and this text should providea reference source and a resource whenever a new material or a new problem comes totheir attention. The scientist, engineer or graduate student new to the field needs moreexplanation and help. The focus here is on the needs of the industrial scientist and thegraduate student. Some may need to know more about the intrinsic capabilities of micro­scopes of all types, so there is a description of basic imaging principles and of instruments,both classical and those more recently invented. Others may know all about microscopesand little about polymers, so there is a discussion of polymer structure and properties toput the microscopy into context. A brief section on processing of polymers has also beenadded.

As the text has been designed to cater to this wide range of backgrounds, some of thesemore introductory sections will not be for every reader. However, the organization ofchapter and section headings should lead the reader to the information needed, and anextensive index is provided for the same purpose.

The first edition of this book was published twenty years ago, in 1987, and a secondedition was published in 1996. There were many changes between those two editions, butthe advances in microscopy and polymers in the last decade have been even more signifi­cant, requiring major revision. We were pleased when Springer invited us to provide thisthird edition allowing us to bring "Polymer Microscopy" up to date once again. Thisedition follows the same basic principles as the first two, with significant editing of olderwork and inclusion of new material. The rapid development of Scanning Probe Micros­copy (SPM) and complete conversion to digital imaging has most affected the imagecapabilities used for polymers. Additionally, new polymer materials such as nanocom­posites have been developed that require the use of microscopy. Overall it has been anexciting decade for polymer microscopy and our goal is to provide a window to view thesenew technologies.

Chapter 1 provides a brief introduction to polymer materials, processes, morphologyand characterization. Chapter 2 is a concise review of the fundamentals of microscopy,where many important terms are defined. Chapter 3 reviews imaging theory for thereader who wants to understand the nature of image formation in the various types of

vi Preface to the Third Edition

microscopes, with particular reference to imaging polymers and how instrumental param­eters affect results. These chapters are summaries of large fields of science, to make thistext complete, and they contain many references to more specialized texts and reviews.

Chapters 4 and 5 contain the major thrust of the book. Chapter 4 covers specimenpreparation, organized by method with enough detail given to allow a reader to conductsuch preparations.* Many new methods have been added, especially those developed foruse with the SPM and those relating to improvements in cryo-TEM. The references arechosen to provide the best detail and support. Chapter 5 describes the application of thesemethods to the study of specific types of polymers. The organization is by the form ofthe material, as fibers, films, membranes, engineering resins and plastics, composites(including a new section on nanocomposites), emulsions, coatings and adhesives, and highperformance polymers. The emphasis in this chapter is on applications, particularly wheremore than one specimen preparation method or microscopy technique is used.

Chapter 6 is newly named for this edition, "Emerging techniques in polymer micros­copy." The change is to indicate that the chapter includes both techniques that have beenrecently developed and those which are not new but which have not yet been regularlyapplied to polymer materials. These techniques include optical, electron and scanningprobe microscopy techniques. In many of these fields the techniques are still developingvery rapidly and thus future improvement in practice and understanding is likely overthe coming years. Chapter 7 describes how the various microscopies and other analyticaltechniques for investigating polymer structure should be considered together as a systemfor problem solving.

The selection of the authors for this text came from a desire for a comprehensive reviewof polymer microscopy with emphasis on methods and techniques rather than on theresults obtained. The synergism provided by three authors with very different back­grounds is important. One author (LCS) has an industrial focus and a background inchemistry, while another author (DTG) is in an academic environment with a backgroundin polymer physics. A third author (GFM), added for this edition, is a chemist with anindustrial focus, and a specialist in SPM. The major contribution of David Grubb andGreg Meyers has been in Chapters 2, 3 and 6. Linda Sawyer has been responsible forChapters 1,4,5 and 7, with input from her coauthors.

ACKNOWLEDGEMENTS

Special thanks go to the former Microscopy group at Celanese Americas, formerly inSummit, New Jersey, whose efforts over the years provided many of the micrographsused in all three editions of this book. Madge Jamieson (deceased), Roman Brozynskiand Rong T. Chen and corporate support from Celanese Americas and from The DowChemical Company are also gratefully acknowledged.

Micrographs for the third edition are gratefully acknowledged from many colleagues,including: Olga Shaffer (Lehigh University, retired), Barbara Wood (DuPont), KarenWiney (University of Pennsylvania), David Martin (University of Michigan), Christian

*The specimen preparation methods used for microscopy of polymers involve the use ofmany hazardous and toxic chemicals as well as the use of instruments which can be radiationhazards. It is well beyond the scope of this text to provide the information required for theproper and safe handling of such chemicals and instruments. The researcher is strongly encouragedto obtain the required safety information from the chemicals and instrumental manufacturersbefore their use.

Prefaceto the Third Edition vii

Kiibel (Fraunhofer Institute), Ishi Talmon (Technion), David A. Zumbrunnen (ClemsonUniversity), G. Julius Vancso (University of Twente, the Netherlands), Javier GonzalezBenito (Universidad Carlos III de Madrid, Spain), Scot Gould (The Claremont Colleges),Gary Stevens (University of Surrey, UK), Inga Musselman (University of Texas, Dallas),Steven M. Kurtz (Drexel University), Vernon E. Robertson (JEOL, USA), Barbara Petti(Celgard LLC), Viatcheslav Freger (Ben-Gurion University of the Negev), Ron Ander­son (Materials Today), Anne Hiltner (Case Western Reserve University), Francis M.Mirabella (Lyondell Chemical), Eduardo Radovanovic (Universidade Estadual deMaringa'). Greg Meyers would also like to thank Georg Bar of the Dow ChemicalCompany who provided technical advice on SPM content. We would also like to thankthe many colleagues who supplied copies of their papers, advice and input on the contentof this text. Special thanks go to Prof. James P. Oberhauser, Dept. of Chemical Engineer­ing, University of Virginia, who enabled Linda Sawyer to have access to the UVA on-linelibrary and obtain the electronic files needed for this new edition.

Linda Sawyer thanks a very understanding colleague and husband, David Sawyer, who,as with the earlier editions, provided technical advice and support. David Grubb wouldlike to thank his wife, Sally, for her support over all the time spent on this project, andGreg Meyers would like to thank his wife, Debbie, for her support, patience, and under­standing for the time spent on the preparation of the book.

Linda C. SawyerLake Monticello, Virginia

David T. GrubbIthaca, New York

Gregory F. MeyersMidland, Michigan

May 2007

Contents

Color plates appear between pages 306 and 307.

Preface to the Third Edition v

1 Introduction to Polymer Morphology 1

1.1 POLYMER MATERIALS. . . . . . . .. . . . . . . . . . . .. . . . . . . . . . . . 11.1.1 Introduction............................................... 11.1.2 Definitions 2

1.2 POLYMER MORPHOLOGY 31.2.1 Amorphous Polymers 41.2.2 Semicrystalline Polymers 51.2.3 Liquid Crystalline Polymers 71.2.4 Multiphase Polymers 81.2.5 Composites 8

1.3 POLYMER PROCESSES 81.3.1 Fiber and Film Formation 91.3.2 Extrudates and Moldings 11

1.4 POLYMER CHARACTERIZATION 171.4.1 General Techniques 171.4.2 Microscopy Techniques 181.4.3 Specimen Preparation Methods 191.4.4 Applications of Microscopy to Polymers 201.4.5 Emerging Microscopy Techniques 21References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

2 Fundamentals of Microscopy 27

2.1 INTRODUCTION 282.1.1 Lens-Imaging Microscopes 292.1.2 Scanning-Imaging Microscopes 30

2.2 OPTICAL MICROSCOPY 312.2.1 Introduction............................................... 312.2.2 Objective Lenses 322.2.3 Imaging Modes 322.2.4 Measurement of Refractive Index 342.2.5 Polarizing Microscopy 34

x Contents

2.3 SCANNING ELECTRON MICROSCOPY 352.3.1 Introduction ... .. . . . .. . .. . . . . .. . . . . . . . . . . . . ... . ... . .. . . . . . . 352.3.2 Imaging Signals 372.3.3 Electron Sources 392.3.4 SEM Types 412.3.5 SEM Optimization 41

2.4 TRANSMISSION ELECTRON MICROSCOPY 422.4.1 Conventional TEM 422.4.2 Scanning TEM 432.4.3 Electron Diffraction 442.4.4 High Resolution Electron Microscopy 45

2.5 SCANNING PROBE MICROSCOPY 452.5.1 Introduction... ... .. .......... . . . ... .. . . . . . . ... . . . .. . ... . . . 452.5.2 Atomic Force Microscopy ". . 472.5.3 SPM Probes 50

2.6 RADIATION SENSITIVE MATERIALS 512.6.1 SEM Operation 522.6.2 Low Dose TEM Operation 52

2.7 ANALYTICAL MICROSCOPY 532.7.1 X-ray Microanalysis 532.7.2 X-ray Analysis: SEM versus AEM 552.7.3 Elemental Mapping 55

2.8 QUANTITATIVE MICROSCOPY 562.8.1 Image Processing and Analysis 562.8.2 Three Dimen sional Reconstruction 572.8.3 Calibration ....... . ... . . .... . .. . . . ........... . .. . .. . . .. ... . 57

2.9 DYNAMIC MICROSCOPY 592.9.1 Mechanical Deformation Stages 592.9.2 Hot and Cold Stages 60References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

3 Image Formation in the Microscope 67

3.1 IMAGING WITH LENSES 683.1.1 Basic Optics 683.1.2 Diffraction 683.1.3 Image Formation 713.1.4 Resolution and Contrast 723.1.5 Phase Contrast and Lattice Imaging 763.1.6 D1umination Systems 783.1.7 Polarized Light 80

3.2 IMAGING BY SCANNING ELECTRON BEAM 853.2.1 Probe Formation 853.2.2 Probe-Specimen Interactions 883.2.3 Image Formation in the SEM 923.2.4 Low Voltage SEM 943.2.5 Variable Pressure SEM 96

3.3 IMAGING IN TH E ATOMIC FORCE MICROSCOPE 973.3.1 Microscope Components 973.3.2 Probe-Specimen Interaction 100

Contents Xl

3.3.3 Contact Mode AFM 1023.3.4 Intermittent Contact AFM 1053.3.5 Noncontact AFM 1123.3.6 Practical Considerations for AFM Imaging 1133.3.7 Artifacts in SPM Imaging 114

3.4 SPECIMEN DAMAGE IN THE MICROSCOPE 1183.4.1 Effect of Radiation on Polymers 1183.4.2 Radiation Doses and Specimen Heating . . . . . . . . . . . . . . . . 1203.4.3 Effects of Radiation Damage on the Image 1213.4.4 Noise Limited Resolution 123References ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

4 Specimen Preparation Methods 130

4.1 SIMPLE PREPARATION METHODS 1324.1.1 Optical Preparations 1324.1.2 SEM Preparations 1334.1.3 TEM Preparations 1334.1.4 SPM Preparations 140

4.2 POLISHING 1424.2.1 Limiting Artifacts 1424.2.2 Polishing Specimen Surfaces 143

4.3 MICROTOMY 1464.3.1 Peelback of FiberslFilms for SEM 1464.3.2 Microtomy for OM 1474.3.3 Microtomy for SEM 1504.3.4 Microtomy for TEM and SPM 1504.3.5 Cryomicrotomy for TEM and SPM 1544.3.6 Microtomy for SPM 1584.3.7 Limiting Artifacts in Microtomy 160

4.4 STAINING 1604.4.1 Introduction............................................... 1604.4.2 Osmium Tetroxide 1624.4.3 Ruthenium Tetroxide 1664.4.4 Chlorosulfonic Acid and Uranyl Acetate 1734.4.5 Phosphotungstic Acid 1754.4.6 Ebonite................................................... 1774.4.7 Silver Sulfide 1784.4.8 Mercuric Trifluoroacetate 1784.4.9 Iodine and Bromine 1794.4.10 Summary 179

4.5 ETCHING 1814.5.1 Solvent and Chemical Etching 1814.5.2 Acid Etching: Overview 1834.5.3 Permanganate Etching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1844.5.4 Plasma and Ion Etching 1884.5.5 Focused Ion Beam Etching 1944.5.6 Summary 195

4.6 REPLICATION 1964.6.1 Simple Replicas 1974.6.2 Replication for TEM 198

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4.7 CONDUCTIVE COATINGS 2014.7.1 Coating Devices 2024.7.2 Coatings for TEM 2034.7.3 Coatings for SEM and STM 2034.7.4 Artifacts 2074.7.5 Gold Decoration 211

4.8 YIELDING AND FRACTURE . .. ...... .. .. . ... . . .. ... .. . .. .. . . . . 2124.8.1 Fractography 2124.8.2 Fracture: Standard Physical Testing 2134.8.3 Crazing 2174.8.4 In Situ Deformation 221

4.9 CRYOGENIC AND DRYING METHOD S 2264.9.1 Simple Freezing Methods 2264.9.2 Freeze Drying 2274.9.3 Critical Point Drying 2304.9.4 Freeze Fracture-Etching 2314.9.5 Cryomicroscopy 232References " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234

5 Applications of Microscopy to Polymers 248

5.1 FIBERS 2505.1.1 Introduction. .. .. . . .. . .. ... . .. . . . ... ... . . ...... . . . . . . . . . . . . 2505.1.2 Textile Fibers 2515.1.3 Problem Solving Applications 2605.1.4 Industrial Fibers 2675.1.5 High Performance Fibers 270

5.2 FILMS AN D MEMBRANES 2765.2.1 Introduction.... . . . .. . .... .. . . .... . . ... ..... . . ....... . . . . . . 2765.2.2 Model Studies 2785.2.3 Industrial Films 2825.2.4 Flat Film Membranes 2945.2.5 Hollow Fiber Membranes 305

5.3 ENGINEERING RESINS AND PLASTICS 3085.3.1 Introduction . . . .. ...... . . . . . . ... . . . . . . . . . .. . ..... .. . . . . . . . . 3085.3.2 Process-Structure Considerations 3115.3.3 Single Phase Polymers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3165.3.4 Multiphase Polymers 3215.3.5 Failure or Competitive Analysis 349

5.4 COMPOSITES 3545.4.1 Introduction. . . .. . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . 3545.4.2 Literature Review 3555.4.3 Composite Characterization 3575.4.4 Carbon and Graphite Fiber Composites 3655.4.5 Particle Filled Composites 3665.4.6 Nanocomposites 370

5.5 EMULSIO NS, COATINGS AND ADHESIVES 3805.5.1 Introduction . ........ .. . .. ...... . . . . . . .. . . . . . . . .. . .. . . . . . . . 3805.5.2 Emulsions and Latexes 3815.5.3 Particle Size Measurements 385

Contents xiii

5.5.4 Adhesives and Adhesion 3865.5.5 Wettability and Coatings 388

5.6 HIGH PERFORMANCE POLYMERS 3985.6.1 Introduction............................................... 3985.6.2 Microstructure of LCPs 4005.6.3 Molded Parts and Extrudates 4035.6.4 High Modulus Fibers 4095.6.5 Structure-Property Relations in LCPs 412References .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 418

6 Emerging Techniques in Polymer Microscopy 435

6.1 INTRODUCTION 4356.2 OPTICAL AND ELECTRON MICROSCOPY 436

6.2.1 Confocal Scanning Microscopy 4366.2.2 Optical Profilometry 4376.2.3 Birefringence Imaging 4386.2.4 Aberration Corrected Electron Microscopy. . . . . . . . . . . . . . . . . . . . 4386.2.5 Ion Microscopy 440

6.3 SCANNING PROBE MICROSCOPY 4416.3.1 Chemical Force Microscopy 4416.3.2 Harmonic Imaging 4436.3.3 Fast Scanning SPM 4446.3.4 Scanning Thermal Microscopy 4456.3.5 Near Field Scanning Optical Microscopy 4496.3.6 Automated SPM 449

6.4 THREE DIMENSIONAL IMAGING. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4516.4.1 Introduction............................................... 4516.4.2 Physical Sectioning 4526.4.3 Optical Sectioning 4546.4.4 Tomography 455

6.5 ANALYTICAL IMAGING 4596.5.1 FTIR Microscopy 4596.5.2 Raman Microscopy 4606.5.3 Electron Energy Loss Microscopy 4616.5.4 X-ray Microscopy 4626.5.5 Imaging Surface Analysis 464References 468

7 Problem Solving Summary 478

7.1 WHERE TO START 4797.1.1 Problem Solving Protocol 4797.1.2 Polymer Structures 480

7.2 INSTRUMENTAL TECHNIQUES...... . . . . . . . 4807.2.1 Comparison of Techniques 4807.2.2 Optical Techniques. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4847.2.3 SEM Techniques 4857.2.4 TEM Techniques 4867.2.5 SPM Techniques 4877.2.6 Technique Selection 487

xiv Contents

7.3 INTERPRETATION .7.3.1 Artifacts .7.3.2 Summary .

7.4 SUPPORTING CHARACTERIZATIONS .7.4.1 X-ray Diffractiou .7.4.2 Thermal Analysis .7.4.3 Spectroscopy .7.4.4 Small Angle Scattering .7.4.5 Summary .References .

488489492492493495496499500501

Appendices

Appendix IAppendix IIAppendix IIIAppendix IV

Appendix V

Appendix VI

Appendix VII

Index

Abbreviation of Polymer Names .Acronyms of Techniques .Manmade Polymer Fibers .Common Commercial Polymers andTrade Names for Plastics, Films, andEngineering Resins .General Suppliers of MicroscopyAccessories .Suppliers of Optical and ElectronMicroscopes, Microanalysis Equipment,Image Analysis and Processing .Suppliers of Scanning Probe Microscopesand Related Supplies .

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