Synthesis and characterization of polybutadiene-containing polyurethanes.

Abstract

Synthesis and Characterization of Polybutadiene-Containing Polyurethanes February 1981 Mark B. Rossman B.S, University of Massachusetts M.S. University of Massachusetts Directed by: Prof. William J. MacKnight Prof. Robert W. Lenz Several segmented polyurethanes have been synthesized, based on a variety of hydroxyl-terminated polybutadienes (HTPB) , two of which included a free radically polymerized, branched polybutadiene with an average functionality of 2.1, and a hydrogenated derivative. The third was an anionically polymerized, high vinyl content polybutadiene with an average functionality of 1.9. Polyurethanes were prepared in bulk, without added catalyst, by a two-step process, where first the HTPB was endcapped with an excess of 2,4-toluenediisocyanate followed by chain extension by 1 , 4-butanediol . Series of samples of varying hard segment (urethane) content were prepared by this method. Structure-property relationships for these materials were studied by mechanical, thermal, and spectroscopic methods. Results indicated that the polyurethanes were well phase separated. The complete absence of hydrogen bonding within the soft segments, due to the all hydrocarbon nature of the butadiene backbone, promotes this phase sep~ iv aration. In this way, the extent of hydrogen bonding, which occurs only in the hard segment domains, is an indication of the degree of phase separation in these systems . Synthesis of model hydroxy-telechelic prepolymers via a Grignard coupling reaction was also investigated. This novel route to linear, difunctional oligomers showed some success , and furthur modification of the procedure may pro duce materials suitable for preparation of polyurethanes .