A new synthetic procedure is proposed to graft polymer chains onto poly(methyl methacrylate) based on the reaction of methyl esters with quaternary ammonium salts (MEQA reaction) under nonprotic conditions. Mechanistic insight into the MEQA reaction has been given by performing model reactions, for example with methyl benzoate and the N-butylammonium salt of 1,4-diazabicyclo[2.2.2]octane. This reaction has been used to graft poly(tetrahydrofuran) with a 1,4-diazabicyclo[2.2.2]octane end group, synthesized from living cationic ring-opening polymerization, on poly(methyl methacrylate) by simply heating the reaction mixture of both components in 1,2-dichlorobenzene as solvent. GPC and NMR analysis demonstrated high grafting yields. The formation of the grafted structures was further evidenced by a comparative DSC study of the crystallization behavior of the starting and end products.