Preparation and properties of ABA block polymers of styrene and butadiene or isoprene made with sec-C4H9Li·2(C2H5)2O
Article first published online: 9 MAR 2003
Copyright © 1972 John Wiley & Sons, Inc.
Journal of Applied Polymer Science
Volume 16, Issue 1, pages 107–112, January 1972
How to Cite
Cunningham, R. E. and Wise, M. L. (1972), Preparation and properties of ABA block polymers of styrene and butadiene or isoprene made with sec-C4H9Li·2(C2H5)2O. J. Appl. Polym. Sci., 16: 107–112. doi: 10.1002/app.1972.070160110
- Issue published online: 9 MAR 2003
- Article first published online: 9 MAR 2003
- Manuscript Revised: 10 SEP 1971
- Manuscript Received: 15 JUL 1971
ABA-type “tapered” block polymers were prepared from styrene (monomer A) and butadiene or isoprene, using an initiator of sec-butyllithium complexed with two molecules of ethyl ether. The stress–strain curves of polymers containing about 20–50% styrene show the usual resemblance to curves of crosslinked elastomers. The SBS polymers had higher tensile strengths than the SIS polymers. They also had slightly higher tensile strengths than comparable SBS polymers made with sec-butyllithium. The SIS polymers, however, had generally lower tensile strengths than those made with sec-butyllithium. This is probably caused by higher styrene content of the isoprene block, brought about by increased randomization of the styrene–isoprene copolymerization due to the presence of the ether. The A and B blocks become more compatible, producing loss of strength in the polymer. Infrared analyses of polydienes made with the sec-C4H9Li·2(C2H5)2O initiator showed a 6% to 8% increase in 1,2-content (for polybutadiene) or 3,4-content (for polyisoprene), compared to polymers made with sec-butyllithium. The polymer microstructures still have high (>80%) total 1,4-content, however. Thus, this amount of ether can be tolerated in the polymerization system without great loss of rubbery properties or block structure in the resultant polymers.