The reaction between ’living’ t-butyl acrylic anions and benzaldehyde (BZA) is shown to be highly selective. Advantage is taken of this fact in order to prepare well defined hydroxyl-terminated poly(t-butyl acrylate) (tBuA) samples. When a dialdehyde such as terephthalaldehyde (TAP) is used in place of BZA, both aldehyde functions of the electrophilic reagent participate in the deactivating reaction of the acrylic anions. Multiblock copolymers consisting of polyvinylic and poly(t-butyl acrylate) sequences can therefore be obtained by stoichiometric coupling reactions between the ’living’ triblock copolymer and terephthalaldehyde.