Hyperbranched polyurethanes with varying spacer segments between the branching points
Article first published online: 21 JAN 2000
Copyright © 1996 John Wiley & Sons, Inc.
Journal of Polymer Science Part A: Polymer Chemistry
Volume 34, Issue 5, pages 839–848, 15 April 1996
How to Cite
Kumar, A. and Ramakrishnan, S. (1996), Hyperbranched polyurethanes with varying spacer segments between the branching points. J. Polym. Sci. A Polym. Chem., 34: 839–848. doi: 10.1002/(SICI)1099-0518(19960415)34:5<839::AID-POLA13>3.0.CO;2-J
- Issue published online: 21 JAN 2000
- Article first published online: 21 JAN 2000
- Manuscript Accepted: 21 SEP 1995
- Manuscript Received: 8 JUN 1995
- Dept. of Science and Technology, New Delhi
- hyperbranched polyurethanes;
- carbonyl azide;
- pendant mesogens
Hyperbranched polyurethanes, with varying oligoethyleneoxy spacer segments between the branching points, have been synthesized by a one-pot approach starting from the appropriately designed carbonyl azide that incorporates the different spacer segments. The structures of monomers and polymers were confirmed by IR and 1H-NMR spectroscopy. The solution viscosity of the polymers suggested that they were of reasonably high molecular weight. Reversal of terminal functional groups was achieved by preparing the appropriate monohydroxy dicarbonyl azide monomer. The large number of terminal isocyanate groups at the chain ends of such hyperbranched macromolecules caused them to crosslink prior to its isolation. However, carrying out the polymerization in the presence of 1 equiv of a capping agent, such as an alcohol, resulted in soluble polymers with carbamate chain ends. Using a biphenyl-containing alcohol as a capping agent, we have also prepared novel hyperbranched polyurethanes with pendant mesogenic segments. These mesogen-containing polyurethanes, however, did not exhibit liquid crystallinity probably due to the wholly aromatic rigid polymer backbone. © 1996 John Wiley & Sons, Inc.