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)-bloch-poly(methyl me thacrylate) triblock copolymers (MnBM) have been synthesized by the sequent ial 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 (d iethyl meso-2,5-dibromoadipate) initiator in the presence of the NiBr2(PPh3 )(2) catalyst. After isolation, the alpha,omega-dibromo poly(n-butyl acryla te) chains have been used as macroinitiators for the polymerization of eith er n-BuA or MMA leading to chain extension or to the desired triblock copol ymers, respectively. The kinetic study of the two-step process has shown th at the initiation of the MMA polymerization by the poly(n-BuA) macroinitiat or is slow and leads to PMMA outer blocks of broad polydispersity. Differen tial scanning calorimetry (DSC) and dynamical mechanical analysis (DMA) hav e confirmed the two-phase morphology of the triblocks. Finally, DMA and ten sile testing of these copolymers have emphasized poor mechanical properties in possible relation to the broad polydispersity of the PMMA outer blocks.