Composites consisting of the tri-block copolymer thermoplastic elastomer poly(methyl methacrylate)-b-poly(butyl acrylate)-b-poly(methyl methacrylate) (PMMA-b-PBA-b-PMMA) and carbon nanotubes modified with either poly(butyl acrylate) homopolymer or with poly(butyl acrylate)-b-poly(methyl methacrylate) block copolymer were prepared and their viscoelastic and photoactuating properties were investigated. Carbon nanotubes modified with PBA homopolymer were prepared by surface initiated atom transfer radical polymerization (SI-ATRP) and subsequently mixed with PMMA-b-PBA-b-PMMA matrix prepared also using ATRP. Carbon nanotubes modified with PBA-b-PMMA diblock copolymer were prepared by SI-ATRP in the presence of free bifunctional ATRP initiator. Thus the modification of carbon nanotubes was performed in situ during synthesis of PMMA-b-PBA-b-PMMA triblock copolymer leading to direct formation of a composite with superior filler dispersion and distribution. The viscoelastic properties of both types of composites were evaluated by dynamic mechanical analysis and melt rheology and compared to pure polymer matrix and composite containing neat carbon nanotubes. Finally photoactuating behaviour of the composites was studied using thermomechanical analysis device. The best storage modulus in broad temperature range and the best photoactuation performance were found for composite containing carbon nanotubes grafted by PBA-b-PMMA diblock copolymer. (C) 2015 Elsevier Ltd. All rights reserved.