Synthesis and characterization of poly(methyl methacrylate)-block-poly(n-butyl acrylate)-block-poly(methyl methacrylate) copolymers by two-step controlled radical polymerization (ATRP) catalyzed by NiBr2(PPh3)2, 1+

Poly(methyl methacrylate)-block-poly(n-butyl acrylate)-block-poly(methyl methacrylate) triblock copolymers (MnBM) have been synthesized by the sequential controlled radical polymerization (atom transfer radical polymerization, ATRP) of n-butyl acrylate (n-BuA) followed by methyl methacrylate (MMA). The polymerization of n-BuA has been first initiated by the difunctional (diethyl meso-2,5-dibromoadipate) initiator in the presence of the NiBr2(PPh3)2 catalyst. After isolation, the α,ω-dibromo poly(n-butyl acrylate) chains have been used as macroinitiators for the polymerization of either n-BuA or MMA leading to chain extension or to the desired triblock copolymers, respectively. The kinetic study of the two-step process has shown that the initiation of the MMA polymerization by the poly(n-BuA) macroinitiator is slow and leads to PMMA outer blocks of broad polydispersity. Differential scanning calorimetry (DSC) and dynamical mechanical analysis (DMA) have confirmed the two-phase morphology of the triblocks. Finally, DMA and tensile testing of these copolymers have emphasized poor mechanical properties in possible relation to the broad polydispersity of the PMMA outer blocks.