Abstract: A novel method of preparing an aqueous dispersion of non-uniform polyurethane particles which comprises (a) preparing at least two isocyanate-terminated polyurethane prepolymers having different hydrophilicities; (b) preparing a uniform mixture of said prepolymers; and (c) dispersing the mixed prepolymers in an aqueous medium. The resulting dispersion of the prepolymers may optionally be chain extended. This method enables the preparation of core-shell particles as well as particles of other morphologies, including “raspberry”, interpenetrating network, “salt-and-pepper”, “ice-cream cone” and particles of gradient composition. Similarly, an aqueous dispersion of two different polyurethane polymers may be obtained by first preparing at least two different isocyanate-terminated polyurethane prepolymers, preparing a uniform mixture of such prepolymers and thereafter dispersing the mixture in an aqueous medium.

Abstract: The synthesis and characterization of novel higher order, multi-arm star polymers comprising polyisobutylene arms connected to condensed cyclosiloxane cores are described. The synthesis has been achieved by hydrosilating olefin-capped (e.g., allyl- or isopropenyl-terminated) polyisobutylene with hydrogencyclosiloxanes carrying a plurality of Si--H groups and simultaneously and competitively converting SiH functions, in the presence of moisture, to Si--OH groups to rapidly self-condense or react with SiH groups to form coupled cyclosiloxane cores via core-core coupling. Thus, higher order stars having many more arms than first order stars can be formed.

Abstract: The synthesis and characterization of novel multi-arm star polymers comprising polyisobutylene arms connected to a well-defined, siloxane core are described. The synthesis has been achieved by hydrosilating olefin-capped (e.g., allyl- or isopropenyl-terminated) polyisobutylene with siloxanes carrying a plurality of Si--H groups.