SYNTHESIS AND CHARACTERIZATION OF MODEL 8- AND 12-ARM STAR-SHAPED POLYISOPRENES.

The successful synthesis of 8- and 12-arm polyisoprene stars has been reported by Hadjichristidis and coworkers. The linking agents used were Si left bracket CH//2CH//2SiCl//3 right bracket //4 and Si left bracket CH//2CH//2SiCl//2CH//3 right bracket //4 which were prepared by the hydrosilation of tetravinylsilane with the appropriate chlorosilane. This paper presents results of an experimental study pertaining to the dilute solution properties and melt viscosity behavior for these 8- and 12-arm polyisoprene stars. The melt vicosity measurements were carried out on the Rheometrics Mechanical Spectrometer at 60 degree C. Both the dynamic and parallel plate modes were used. The values reported are from the Newtonian region. Data are presented which demonstrate that the bulk viscosity of branched polyisoprene is independent of the degree of branching. At present not suitable model exists for multiple branched star molecules, either in the melt or in solution, especially as the number of branch