SYNTHESIS AND CHARACTERIZATION OF NEW POLYSILOXANE STARBURST POLYMERS

New, highly branched polysiloxane starburst polymers were synthesized starting from tris[(phenyldimethylsiloxy)dimethylsiloxy]methylsilane and bis[(phenyldimethylsiloxy)methylsiloxy]dimethylsilanol as the initiator core (G0-Ph) and the building block, respectively. In this case, the phenylsilane moiety was a synthon of N,N-diethylaminosilane, which was a suitable electrophilic silicon species. The phenylsilane of G0-Ph was converted to the (N,N-diethylamino)silane (G0-DEA) via the corresponding bromosilane (G0-Br) generated by the reaction of G0-Ph with bromine. Next, the silanol of the building block was reacted with the aminosilane of G0-DEA, yielding the first generation polymer (G1-Ph), which contained twice the amount of phenylsilyl groups in the exterior layer than did G0-Ph. The higher generation polymers could be builtup by repeating the same reactions. Thus, the third generation polymer (G3-Ph) possessed 24 phenylsilyl groups. G0-Ph and G1-Ph were purified by vacuum distillation, whereas G2-Ph and G3-Ph were purified by preparative gel permeation chromatography (GPC). The H-1, C-13, and Si-29 NMR spectra of all the starburst polymers were consistent with the proposed structures. The Mark-Houwink constants K and alpha, calculated from the relationship between the molecular weight and intrinsic viscosity of the polymers, were found to be 4.7 x 10(-3) and 0.21, respectively. The molecular weight of the polymers of all generations measured by GPC using polystyrene standards was proportional to their size based on the Corey-Pauling-Koltun (CPK) model.