Synthesis and properties of regular star polybutadienes with 32 arms

A dendrimer carbosilane containing 32 Si-Cl bonds in the perimeter has been prepared and has been used as a coupling agent to prepare 32-arm star polybutadienes. The dilute-solution properties 〈R _G ² 〉, A ₂ , [η], and D ₀ have been measured in one good solvent and in one θ-solvent. The dimensions of the 32-arm star polymers are compared with those of linear polymers at constant molecular weight. It is shown that the 32-arm star polybutadiene has the characteristic properties of a hard-sphere molecule in dilute solution. The equivalent hard-sphere radii calculated from A ₂ , D ₀ and [η] are identical and 1.29 times larger than the root mean-square radius of gyration. The Daoud-Cotton scaling model for stars is also tested.