PREFACE This work has been edited and organized to provide a solid understanding of the main concepts of polymeric materials at an introductory level,suitable for undergraduate and beginning graduate students in disciplines ranging from chemistry and chemical engineer- ing to materials science,polymer engineering,and mechanical engineering.The second edition of the textbook was organized in a way that flowed naturally from molecular-level considerations to bulk properties,mechanical behavior,and processing methods.I have kept that organization intact with this third edition.I have used this book in teaching a polymer materials engineering course over the past several years,and find that enough information is presented without overwhelming students in detail (i.e.,for more detailed courses beyond the introductory polymer class). One of the big challenges in updating a textbook is to include some of the newer materials,methods,and issues surrounding polymer science while editing and refining the original material so that the end product remains fairly streamlined and provides a balance between describing theories and methodologies while treating each subject with an appropriate weighting.(Of course,instructors are certainly invited to pick and choose topics for their classes,and add material to that covered in the text,but I hope that this provides a good.solid read for students learning the material for the first time without a significant need to supplement the book on the instructor's behalf and without providing so much information that significant portions of the book must be passed over in a one- semester course. The text should be suitable for advanced undergraduates and beginning graduate students in disciplines ranging from chemical engineering and chemistry to materials science and mechanical engineering.I have taught mixed classes with just this background using the second edition,and usually found that some introductory information(such as organic chemical structures)was needed-both for students who had not been formally trained in organic chemistry and for those who needed a refresher.This edition now includes a short section in Chapters 1 and 2 on organic functional groups,with an emphasis on some of the structures found in condensation polymerizations.Several instances of xiii