Over the past four decades polymers containing imide groups (usually as build ing blocks of the polymer backbone) have attracted increasing interest of sci entists engaged in fundamental research as well as that of companies looking into their application and commercialization. This situation will apparently continue in the future and justifies that from time to time reviews be published which sum up the current state of knowledge in this field. Imide groups may impart a variety of useful properties to pol~'mers, e. g. , thermal stability chain stiffness, crystallinity, mesogenic properties, photoreactivity etc. These lead to a broad variety of potential applications. This broad and somewhat heteroge neous field is difficult to cover in one single review or monograph. A rather com prehensive monograph was edited four years ago by K. Mittal, mainly concen trating on procedures and properties of technical interest. Most reviews presented in this volume of Advances in Polymer Science focus on fundamen tal research and touch topics not intensively discussed in the monograph by K. Mittal. Therefore, the editor of this work hopes that the reader will appreci ate finding complementary information. Finally I wish to thank all the contributors who made this work possible and I would like to thank Dr. Gert Schwarz for the revision of the manuscripts of the contributions 3 and 4. Hamburg, September 1998 Hans R. Kricheldorf Contents Nanoporous Polyimides J. L. Hedrick, K. R. Carter, l. W. Labadie, R. D. Miller, W.