Synthesis of well-defined second (G-2) and third (G-3) generation dendritic polybutadienes

A series of well-defined second (G-2) and third (G-3) generation dendritic polybutadienes (PBd) were synthesized by the coupling of the living G-2 and G-3 dendrons with methyltrichlorosilane, using anionic polymerization high-vacuum techniques. The synthetic approach of the living G-2 dendrons involves (a) the synthesis of an in-chain double-bond PBd by selective replacement of the two chlorines of 4-(dichloromethylsilyl)-diphenylethylene (DCMSDPE), a novel linking reagent with dual functionality, with PBd by titration with PBdLi, (b) addition of s-BuLi to the double bond, and finally (c) polymerization of butadiene from the newly created anionic site. The synthesis of the G-3 dendrons requires the repetition of the aforementioned procedure with the exception of the addition of the living G-2 dendron, instead of PBdLi, to DCMSDPE. Intermediate and final products were characterized via size exclusion chromatography, membrane osmometry, size exclusion chromatography equipped with a two-angle laser light scattering detector, and proton nuclear magnetic resonance. The combined characterization results indicate that the dendritic PBds synthesized have high molecular and structural homogeneity.