Synthesis and Characterization of Well-Defined, Regularly Branched Polystyrenes Utilizing Multifunctional Initiators

Abstract

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 T g 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.

Crystallization behavior of hyperbranched polyethylenes with different degree of branching

“…In recent decades, hyperbranched polymers (HBPs) have drawn extensive attention because of their wide applications in various fields, for example, light emitting materials, nanoscience and technology, supramolecular chemistry, biomaterials, hybrid materials and composites, coatings, adhesives, and modifiers . HBPs have exhibited many intriguing physical and chemical properties benefiting from their highly branched architecture with plenty of terminal groups, inner cavities, and lack of chain entanglements . Crystallization is one of the most important properties which affect the physical properties of polymers.…”

Surface segregation driven by molecular architecture asymmetry in polymer blends

“…1, namely, f-star, f-pom, and f-end) [25], involving the use of a novel synthetic method. In group 1 the number of branch points in the molecule was varied from 1 to 3 to 4, while the number of ends was fixed at 6.…”

“…Four types of junctions (described in Ref. [25]) are contained in the molecules. The star molecule contains disilylethylene, which is a flexible core.…”

Star polymers by photoinduced copper-catalyzed azide-alkyne cycloaddition click chemistry

“…S7–S9). The star polymers contain a core molecule that was comparatively rigid, and the presence of this stiff unit would tend to increase the T g or T m values compared to linear precursors owing to the restricted segmental mobility in that region …”