Synthesis and characterization of star polymers with varying arm number, length, and composition from organic and hybrid inorganic/organic multifunctional initiators

Multifunctional initiators, derived from cyclotriphosphazenes, cyclosiloxan es, and organic polyols, were used in the synthesis of styrenic and (meth)a crylic star polymers by atom transfer radical polymerization (ATRP). Condit ions were identified in each system which provided linear first-order kinet ics for polymers with narrow, monomodal molecular weight distributions. Mol ecular weight measurements relative to linear polystyrene standards showed that the star polymers had lower molecular weights than theoretically predi cted. Triple detection SEC measured on poly(n-butyl acrylate) samples demon strated that the absolute molecular weight matched the theoretical value-th e smaller relative chain length was due to lower hydrodynamic volumes of th e star-branched polymers relative to Linear analogues. Kinetic arguments we re used to demonstrate that each alkyl halide moiety bound to the initiator s was participating in ATRP. Well-defined poly(methyl acrylate) stars of mo lecular weights M-n > 500 000 and low polydispersity (M-w/M-n < 1.2) have b een prepared. Star-block copolymers with a soft poly(methyl acrylate) core and a hard poly(isobornyl acrylate) shell were also synthesized.