Polydimethylsiloxanes of narrow molecular-weight distribution and with primary and secondary amine end groups will be prepared by initiating the anionic polymerization of the cyclic trimer, hexamethylcyclotrisiloxane, with lithium bases containing protected nitrogen. After polymerization, the protecting group will be removed and the amino-ended silicones will be converted to block copolymers. Such copolymers will be composed of rubbery silicone segments and polar, rigid segments which should undergo microphase separation. Silicone- polyurethane and silicone-polyurea block copolymers will be prepared. These will be examined by small-angle x-ray scattering, thermal-mechanical analysis, and dynamic-mechanical analysis. Fundamental relationships between molecular weight of silicone or hard segment and separated domain size and thermal- mechanical properties will be derived. This research project is part of the NSF effort to enhance support for undergraduate research.
