POLYURETHAN ELASTOMERS579
Vol. 3, N o . 5, September-October 1970
Infrared Studies of Segmented Polyurethan Elastomers. I. Hydrogen Bonding R. W. Seymour, G . M. Estes, and S. L. Cooper* Depurtnient of Chemicul Engineering, Unirersirj. of Wisconsin, Mudison, Wisconsin 53706. Received March 31, 1970
ABSTRACT: An analysis of hydrogen bonding in segmented polyether and polyester urethan elastomers is presented. Hydrogen bonds may form in these materials between the active hydrogen on the urethan nitrogen
and either the urethan carbonyl or the prepolymer ester or ether linkage. Investigations of the infrared absorption due to the urethan N-H stretching vibration indicate that almost all of these groups are hydrogen bonded, while study of the urethan carbonyl shows that only about 60% of these groups are similarly associated. The conclusion is that substantial hydrogen bonding must occur between the urethan N-H and the appropriate prepolymer linkages. The constancy of hydrogen bonding in samples stretched to 300% indicates that clinnges in the extent of hydrogen bonding do not play an important part in determining observed elastic properties.
I
t has been p r o p o ~ e d l -that ~ the elastic properties of linear urethan block copolymers arise from a twophase microstructure, in which the hard (urethan based) segments separate from the soft segment matrix to form domains. It is presumed that these hard domains act as physical cross-links, imparting the observed elastic properties. Several experimental techniques have been employed to study these materials, including X-ray diffraction$-' birefringence,8 modulus-temperature, and dynamic thermal methods. l o It has been generally concluded that the postulated domain structure does exist, in varying degrees, and that secondary bonding is important in determining the domain structure. This paper reports investigations into the nature and behavior of hydrogen bonding in segmented polyether and polyester urethan elastomers. Literature Review The extent arid nature of hydrogen bonding in polyether and polyester urethans have been the subject of several recent investigations. l l--l; Essentially complete
*
To whom correspondence should be addressed.
( I ) S. L. Coopt:r and A. V. Tobolsky, J . Appl. Polvm. Sci., 10, 1837(1966). (2) S. L. Coopcr and A. V. Tobolsky, Text. Res. J., 38, 800 (1966). (3)'A. M. North, J. C. Reid, and J. B. Shorthall, Eur. Polyrn. J., 5,565 (1969). (4) G. M. Estes. S . L. Cooper, and A. V. Tobolsky, J . Mucromol. Sci., Rea. Mucromol. Chem., C4 (1). 167 (1970). ( 5 ) R. Bonart, J . Macromol. Sci. fhj,s., B2 ( l ) , 115 (1968). (6) R. Bonart, I-. Morbitzer, and G.Hentze, ibid.. B3 (2), 337 (1969). (7)'s. B. Clough, N. S. Schneider, and A. 0. King, ibid., B2 (4), 641 (1968). (8) G. M. Estes, R. W. Seymour, D. S. Huh, and S. L. Cooper, Polym. Eng. Sci., 9,383 (1969). (9) G. ,M. Estes, D. S. Huh, and S. L. Cooper, "Block S. L . Aggarwal, Ed., Plenum Publishing Co., Polymers, New York, N. Y., 1970. p 2 2 5 . ( 1 0 ) S. B. Clough and N. S. Schneider, J . Macrontol. Sci. Phys., B2 (41,553 (1968). (11) Yu. M. Boyarchuk, L. Ya. Rappoport, V. N. Nikitin, and N. P. Apukhtine, Pol.i,m. Sci. U S S R , 7, 859 (1965). (12) T. Tanaka, T. Yokoyama, and Y . Yarnuguchi, J . Polym. Sci., Part A - I , 6,2137 (1968). (13) T. Tanaka, T, Yokoyama, and I
