Recent Advances in Polymer Blends, Grafts, and Blocks
Polymer blends, grafts, and blocks, broadly defined, encompass all of the ways in which two or more kinds of poly mer molecules can be mixed and/or joined. Because these mate rials exhibit non-linear and often synergistic properties, they have found inc
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RECENT ADVANCES IN POLYMER BLENDS, GRAFTS, AND BLOCKS
POLYMER SCIENCE AND TECHNOLOGY
Editorial Board: C. A. J. Hoeve Polymer Research Center Department of Chemistry Texas A&M University College Station. Texas
William J. Bailey Department of Chemistry University of Maryland College Park. Maryland
J. P. Berry Rubber and Plastics Research Association of Great Britain Shawbury Shrewsbury. England
Yoichi Ishida Department of Polymer Science Faculty of Science Osaka University Toyonaka. Osaka. Japan
A. T. DiBenedetto Department of Chemical Engineering School of Engineering The University of Connecticut Storrs. Connecticut
Frank E. Karasz Polymer Science and Engineering Goessmann Laboratory University of Massachusetts Amherst. Massachusetts
Osias Solomon Poly technical Institute of Bucharest Bucharest. Romania
Volume 1. STRUCTURE AND PROPERTIES OF POLYMER FILMS Edited by Robert W. Lenz and Richard S. Stein. 1972 Volume 2. WATER-SOLUBLE POLYMERS Edited by N. M. Bikales. 1973 Volume 3 • POLYMERS AND ECOLOGICAL PROBLEMS Edited by James Guillet. 1973 Volume 4. RECENT ADVANCES IN POLYMER BLENDS, GRAFTS, AND BLOCKS Edited by L. H. Sperling. 1974
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POLYMER SCIENCE AND TECHNOLOGY Volume 4
RECENT ADVANCES IN POLYMER BLENDS, GRAFTS, AND BLOCKS
Block copolymer An interesting method for the preparation of poly(methyl methacrylate-Q-acrylonitrile) has been developed (6,7): It was known that tertiary amines are effective transfer agents in the polymerization of acrylonitrile, but are much less active with methyl methacrylate. Thus one can prepare, in the presence of sufficiently high amounts of a tertiary amine, poly(methyl methacrylate) molecules terminated by tertiary amine end groups, which in turn can be used as transfer sites in a polymerization of acrylonitrile. The following equations summarize these steps:
SYNTHESIS OF BLOCK AND GRAFT COPOLYMERS
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block copolymer of MMA + AN This technique of block copolymer synthesis, of course, can be successful only when the chain transfer activity of amine (or other agent) is significantly different for the two monomers involved. Also, statistical chain transfer to the polymer should be absent. Keeping these principles in mind Bamford and White first polymerized MMA in the presence of Et3N at Et3N/MMA ratio of 14:1 at 60° with AIBN; the excess base was removed and the PMMA isolated. Subsequently the PMMA was dissolved in AN and the second (block) copolymerization initiated by AIBN. Another method for the preparation of graft copolymers by free radical chain transfer is first to prepare a backbone polymer containing halogens (halogens have high transfer activity) and to use these groups in a subsequent grafting reaction as initiating sites. For example Schonfield and Waltcher (8) first synthesized a suitable polyester which contain
