ИСТИНА

Localization and orientation of anisotropic nanoparticles in the matrices of microphase-separated symmetric and asymmetric diblock copolymers AB have been studied using dissipative particle dynamics simulations and a molecular theory. In the simulations the effect of the volume fraction, length, stiffness, and selectivity of nanorods to the copolymer blocks has been investigated. It is demonstrated that while the local composition of the system is mainly determined by the nanorod selectivity, their local orientation is strongly inhomogeneous. Nanorods tend to be aligned along domain boundaries in the areas where their concentration exceeds an average value for the whole composite. In contrast, they align perpendicular to the boundaries in the areas where their content is low. The maximum degree of ordering is achieved for non-selective nanorods near the domain boundary. In the theory (Eur. Phys. J. E 2016, 39, 126) similar peculiarities are predicted for spherical nanoparticles interacting with monomer units via both isotropic and anisotropic potentials, the latter being important when a nanoparticle is located at the A/B interface. There exists the possibility of the mutually perpendicular alignment of nanoparticles in adjacent domains. It has been found that a variation in the selectivity of nanorods with respect to different blocks A and B may result in a change of the microstructure. The effect has a threshold and disappears at low nanorod concentrations. Results of this study suggest that diblock copolymer nanocomposites are characterized by spontaneous organization and orientation of rod-like nanoparticles leading to a spatial modulation of anisotropic composite properties. This creates an opportunity to align block copolymers by external fields which may be helpful for various applications.