118063-73-3Relevant articles and documents
Synthesis and characterization of well-defined, regularly branched polystyrenes utilizing multifunctional initiators
Lee, Jae S.,Quirk, Roderic P.,Foster, Mark D.
, p. 5381 - 5392 (2005)
A series of well-defined, long-branched polystyrenes (PS) of various architectures, but the same overall molecular weight, suited to the systematic study of branching effects, have been synthesized by anionic polymerization and characterized. Three end-branched, star-branched polystyrenes with 6, 9, and 13 end branches were synthesized with a trifunctional organolithium initiator; the synthesis of the 13-end molecule required a recently developed methoxysilyl functionalization and precipitation procedure to remove excess linking agent. In these architectures the number of branch points was fixed at four, while the number of chain ends varied. A 6-end, pom-pom (dumbbell-shaped) PS with two branch points was synthesized with a difunctional organolithium initiator. A regular 6-arm star polystyrene having one branch point was included to provide a comparison among three polymers, each having 6 ends, but having the number of branch points equal to 1, 2, or 4, The intrinsic viscosities and infinite dilution diffusion coefficients (and therefore the branching factors and hydrodynamic radii) decrease with increasing number of chain ends but do not vary monotonically with number of branch points. The values of Tg for the molecules reflect both the effects of tethering by junction points and increases in free volume due to the multiplication of chain ends as well as the presence of butadiene units used to facilitate linking.
