The discoveries of organometallic catalysts for olefin polymerization by Karl Ziegler and that of stereoregular olefin polymers by Giulio Natta are probably the two most important achievements in the areas of catalysis and polymer chemistry in the second half of this century. They led to the development of a new branch of chemical industry, and to a large volume production of high-density and linear low-density polyethylene, isotactic polypropylene, ethylene-propylene rubbers, isotactic poly I-butene, and poly-4-methyl-l-pentene. These discoveries merited the Nobel prize, which was awarded to K. Ziegler and G. Natta in 1963. The initial works of Ziegler and Natta were followed by an "explosion" of scientific papers and patents covering all aspects of polymerization chemistry, catalyst synthesis, and polymerization kinetics as well as the structural, chemical, physical, and technological characteristics of stereo regular polyolefins, polydienes, and olefin copolymers. It is sufficient to say that in the twenty-five years after the first publications more than 15,000 papers and patents appeared on subjects related to the area. . The development brought about the establishment of several prominent groups of scientists occupied with the study of olefin polymerization. The most important of these were scientific schools in Italy, Germany, England, the United States, Japan, the Soviet Union, Czechoslovakia, and Venezuela. In addition, many major chemical and petrochemical corporations throughout the world established labora tories devoted to the development of the technology of catalyst synthesis and olefin polymerization.

Recent development of a new generation of Ziegler-Natta Catalysts using either magnesium dichloride as carrier or methylaluminoxane as cocatalyst has markedly stimulated the research activity in the field of olefin polymerization. These discoveries have not only yielded economical processes for polyolefin production but also opened the way to a new generation of novel polymers. Moreover, the nature of active species is being clarified well by the effort to simplify catalyst systems. The present volume includes 38 papers from the 31 lectures and 18 posters presented at the symposium on `Recent Developments in Olefin Polymerization Catalysts', which covered the following topics: Overview of super-active homogeneous and heterogeneous catalysts, kinetic profile of olefin polymerization including copolymerization, characterization of catalysts and polymers, methods for the determination of active center concentration, role of Lewis bases on the catalysts isospecificity, polymerization mechanisms, and synthetic pathways for functionalized polyolefins. The contents are well balanced between fundamental research and application as well as between homogeneous and heterogeneous catalyst systems.

More than 30 years after the discovery of transition metals and organometal lics as catalysts for olefin polymerization these catalysts did not have lost their fascination. Since 1953 when Karl Ziegler has discovered the catalytic polymerization of ethylene leading to plastically formable polymers which are mechanically stable up to temperatures of about 100°C, synthetic polymers and rubbers have made their way right into private houses. This discovery has been a main impetus for the fast growing production of plastics. The stereoselective poly merization of propylene and other long-chain a-olefins first detected by Giulio Natta leads to an even broadened field of applications. Another enforcing factor were the developments of Standard Oil of Indiana and Phillipps Petroleum Company who engaged in the polymerization of a-olefins supported molybdenum, cobalt and later on chromium catalysts which clearly indicates the wide variety of suitable systems. This kind of research acknowledged merit when in 1963 the Nobel prize of chemistry was awarded to Ziegler and Natta. Although to a great extent there is a technical application for these catalysts, up to now the nature of the active centres and many reaction mechanisms are not completely known.

"Catalysis is more art than science", probably all of you have heard and even used this expression. Whether it is true or not, it alludes to the experience that new catalysts are hard to find, and near impossible to predict. Hard work and a lifetime of experience is invaluable. However, a keen mind might give insight into where to search, but not necessarily about where to find the answers. Historically, "quantum leaps" have often arisen from serendipity - we all know the story about the nickel-contaminated reactor that triggered further research towards the first coordination catalyst for ethene polymerization. Taking advan tage of this event, Karl Ziegler became the first chemist to earn both a Nobel prize and a fortune for the same invention. A broken NMR tube helped Walter Kaminsky discover the effect of high concentrations of methylaluminoxanes as co catalysts for metallocenes. When air reacted with the concentrated trim ethyl aluminum solution, sufficient amounts of methylaluminoxanes were formed, and the lazy catalyst dormant in the NMR tube suddenly became sensationally active. Ziegler and Kaminsky were lucky and had the genius needed to take advantage of their luck.

Recent development of olefin polymerization catalysts has caused marked changes in both industrial and academic research. Industrial use of homogeneous metallocene catalysts has already begun in the fields of high density polyethylene and syndiotactic polypropylene. Moreover, important data have been obtained from academic investigations which have proved useful for understanding conventional heterogeneous Ziegler-Natta catalysts. From the industrial viewpoint, however, heterogeneous high-yield catalysts seem to be more important. The present volume contains invited lectures and contributed papers. The following topics are covered: (1) Heterogeneous Catalysts, (2) Metallocene Catalysts and (3) New Trends in the Polyolefin Industry.