Multifunctional initiators for the ruthenium-mediated living radical polymerization of methyl methacrylate: Di- and trifunctional dichloroacetates for synthesis of multiarmed polymers

Bi- and trifunctional dichloroacetates were synthesized from the corresponding multifunctional alcohols or phenols and-then employed as multifunctional initiators for the living radical polymerizations of methyl methacrylate mediated by RuCl2(PPh3)(3) in the presence of aluminum compounds such as Al(OiPr)(3) and Al(acac)(3) (acac: acetylacetonate). All these systems led to living polymerizations. However, the systems with Al(OiPr)(3) involved partial transesterification of the ester units in the initiators, which resulted in the formation of a monofunctional initiator. In contrast, new systems with Al(acac)(3) did not induce such transesterification and produced the multiarmed living polymers. H-1 NMR analysis showed that polymers obtained with the di-and trifunctional esters possessed almost two and three arms, respectively, along with controlled molecular weights and their narrow distributions.