Design, synthesis, morphology, mechanical properties and in vitro oxidative stability of new class of surface modified thermoplastic elastomers containing mixed soft rubbery poly(n-butyl acrylate-b-dimethylsiloxane-b-n-butyl acrylate) (PnBA-b-PDMS-b-PnBA) block and glassy poly methyl methacrylate (PMMA) end blocks have been reported. Thus well-defined pentablock copolymers such as PMMA-b-PnBA-b-PDMS-b-PnBA-b-PMMA were synthesized by Atom Transfer Radical Polymerization (ATRP). Moderate amount of PDMS (8-15 wt%) in the copolymers significantly enhances the oxidative stability of the surface and contact angle of water in compare to neat PMMA-b-PnBA-b-PMMA copolymer. The phase morphology of such type of copolymers was studied in detailed which suggests that the mixed soft PnBA-b-PDMS-b-PnBA part forms single phase and the degree of phase separation between PnBA-b-PDMS-b-PnBA and PMMA in PMMA-b-PnBA-b-PDMS-b-PnBA-b-PMMA copolymer is higher than the degree of phase separation between PnBA and PMMA in PnBA-b-PDMS-b-PnBA copolymer. This approach of surface modification was extended to synthesize PMMA-b-PLMA-b-PDMS-b-PLMA-b-PMMA (PLMA = polylauryl methacrylate) block copolymers with improved surface properties. (C) 2012 Elsevier Ltd. All rights reserved.