A B S T R A C TTo prepare polyisoprene of controlled microstructure and molecular weight in emulsion systems, a series of polymerizations was carried out with catalyst systems of rhodium complexes and allyl alcohol, with variation of the type of rhodium salts, emulsifiers, and other conditions. A dramatic change in the structure of polyisoprene and also an increase of the polymer yield were brought about by the addition of sodium dodecyl sulfate and allyl alcohol. p-Toluenesulfonic acid and other strong acids exhibited an effect similar to that of the 999 Copyright 0 1977 by Marcel Dekker, Inc. All Rights Reserved. Neither this work nor any part may be reproduced or transmitted in any form or by any meahs, electronic or mechanical, including photocopying, microfilming, and recording, or by any information storage and retrieval system, without permission in writing from the publisher.

Isoprene is polymerized with a catalyst system consisting of a rhodium complex, allyl alcohol, and sodium dodecyl sulfate. The role of the emulsifiers was examined to elucidate the nature of the active species. Sodium dodecyl sulfate was found to be hydrolyzed even in a nonmicellar system to give sulfuric acid. Another experiment showed that isoprene was polymerized also by the catalyst system consisting of rhodium complex, allyl alcohol, and a strong acid such as toluenesulfonic acid, sulfuric acid, or nitric acid. From these results, it was assumed that an allyl ester of the strong acid was formed in the reaction system. The allyl ester presumably reacted with the rhodium complex to form a 1r-allyl complex, which was regarded as the active catalyst species in the isoprene polymerization. Allyl alcohol present in excess in the reaction system seemed to suppress cyclization reactions of the polymer formed.