One-Pot Synthesis of Arborescent Polystyrenes
2006-03-21T00:00:00Z (GMT) by
A new grafting-from procedure was developed for the synthesis of arborescent styrene polymers of successive generations in a single reaction pot. Styrene was first copolymerized anionically in a semibatch process with 1,3-diisopropenylbenzene (DIB), and the chains were terminated with methanol. The pendent isopropenyl moieties of the DIB units were then reacted with sec-butyllithium to generate a polyfunctional anionic macroinitiator. Further additions of styrene−DIB monomer mixture to the activated linear substrate yielded a comb-branched (generation G0) copolymer. After termination of the chain ends and activation of the double bonds on the G0 substrate, styrene monomer was added to generate G1 arborescent polystyrenes, with a dendritic architecture. Alternately, the G0 copolymer was isolated by precipitation and activated in a separate procedure. The size (molecular weight) of the side chains in the G1 polymer was conveniently controlled by varying the amount of monomer added to the G0 macroinitiator. The reaction conditions were optimized to obtain graft polymers with relatively low polydispersity indices (Mw/Mn = 1.1−1.3) and absolute weight-average molecular weights Mw reaching 7 × 106. The intrinsic viscosity in toluene of the arborescent G1 polystyrenes synthesized was up to 7.2 times lower than for linear polystyrene samples of comparable molecular weight.