The influence of carbon nanotube (CNT) modification on the dispersion and localization behavior of the CNTs in immiscible blends of polystyrene (PS) and polybutadiene (PB), and in the nanostructured morphology of a star-shaped styrene-butadiene based block copolymer (BCP), was studied to form a basis for the development of functional materials with defined electrical property profiles. Unmodified multi-walled CNTs (MWCNTs) were dispersed in PS, PB and PS/PB blends by solution mixing. Additionally, MWCNTs were functionalized with n-octadecylamine and monoamino-terminated polystyrene to increase the compatibility between the homopolymers and the nanofiller. The MWCNT dispersion and the blend morphology formation were studied using transmission light microscopy and scanning electron microscopy. The MWCNT dispersion could be significantly improved by the modification of the MWCNTs. All MWCNT types were found to preferably localize in the PS phase of the PS/PB blend. However, only blends containing unmodified MWCNTs were electrically conductive. Similar effects were found in BCP/MWCNT composites. The BCP was already electrically conductive with a filler content of 0.1 wt % of unmodified MWCNTs. The stress-strain behavior of the BCP was slightly influenced by MWCNT addition and CNT modification. The dispersability of MWCNTs was significantly improved by CNT functionalization, which indicates a strong polymer-filler interaction.the filler particles as well as the domain sizes of the phases in the BCP play a decisive role. While spherical (zero-dimensional) filler particles can theoretically be localized in any phase of all possible morphologies, carbon nanotubes (CNTs), which are regarded as one-dimensional in view of their large aspect ratio and the domain size of the BCPs, can only be selectively introduced in lamellar, cylindrical, or co-continuous morphologies in a specific phase. For two-dimensional filler particles such as phyllosilicates, only lamellar BCPs are even considered. The inclusions must have at least one dimension that is of the same order of magnitude as the copolymer microstructure domains (5-100 nm) or smaller in order for a nanocomposite to be formed [2]. Undesirable interactions between the particle surface and the matrix polymer usually require surface modification of the particles for compatibility. The ligands attached to the nanoparticles have a major influence on the interactions.The selective mixing of CNTs aims to improve properties of the BCPs-e.g., mechanical, electrical, or thermal-but also to significantly reduce the required filler content compared to uniform filler dispersion in a BCP matrix, and thus to reduce costs. In addition, a phase in the BCP can be specifically modified in this way, for example to generate electrical or thermal conductive paths in the nanoscale range within an insulating (and e.g., flexible) matrix in oriented BCP structures, or to increase the mechanical strength in the BCP without negatively affecting the elasticity.In recent years, there have been various a...