Ordering of anisotropic nanoparticles in diblock copolymer lamellae: Simulations with dissipative particle dynamics and a molecular theory

Abstract

Short title: Ordering of anisotropic nanoparticles: Simulations and theory a) Corresponding author. Electronic mail: yar@ips.ac.ru 2 ABSTRACT Local distribution and orientation of anisotropic nanoparticles in microphase-separated symmetric diblock copolymers has been simulated using dissipative particle dynamics and analyzed with a molecular theory. It has been demonstrated that nanoparticles are characterized by a non-trivial orientational ordering in the lamellar phase due to their anisotropic interactions with isotropic monomer units. In the simulations, the maximum concentration and degree of ordering are attained for nonselective nanorods near the domain boundary. In this case the nanorods have a certain tendency to align parallel to the interface in the boundary region and perpendicular to it inside the domains. Similar orientation ordering of spherical nanoparticles located at the lamellar interface is predicted by the molecular theory which takes into account that the nanoparticles interact with monomer units via both isotropic and anisotropic potentials. Computer simulations enable one to study the effects of the nanorod concentration, length, stiffness, and selectivity of their interactions with the copolymer components on the phase stability and orientational order of nanoparticles. If the volume fraction of the nanorods is lower than 0.1, they have no effect on the copolymer transition from the disordered state into a lamellar microstructure. Increasing nanorod concentration or nanorod length results in clustering of the nanorods and eventually leads to a macrophase separation, whereas the copolymer preserves its lamellar morphology. Segregated nanorods of length close to the width of the diblock copolymer domains are stacked side by side into smectic layers that fill domain space. Thus, spontaneous organization and orientation of nanorods leads to a spatial modulation of anisotropic composite properties creating an opportunity to align block copolymers by external fields which may be important for various applications.

Orientational ordering of nanorods in diblock copolymers

“…The NPs may be ordered also inside the domains if one of their ends is close to the interface and can interact with the monomers in the adjacent block. In general, the order parameter and the concentration profiles, obtained in this paper, are closer to the results of computer simulations [29] than the results of our previous study [28]. One notes that in the computer simulations the NPs are also ordered inside the blocks.…”

“…In fact, these NPs are composed of 5 spheres which is of the same order as the periodicity of the simulated lamellae structure [29]. In contrast, in the theoretical model the NPs are assumed to possess the spherical shape.…”

Spectral properties of nanocomposites based on fluorine-containing polymer and gold nanoparticles

“…As was shown previously, polymers nanocomposites containing in their composition metal nanoparticles with have a high permittivity due to the high polarizability of the metal nanoparticles [7]. This function is of interest not only for electronic and microelectronic applications, but for light-conversion technologies.…”

“…At the heart of modern nanocomposites, as a rule, there are substances capable of forming highly ordered structures with a certain geometry (alternating flat layers, filaments, point inclusions, more complex compositions). [11]. In this study, we use technique of forming nanocomposites of gold nanoparticles in a polymer matrix, based on laser ablation of solid targets in liquids [12].…”

Phase behavior and orientational ordering in block copolymers doped with anisotropic nanoparticles

“…On the other hand, they may also affect the thermodynamic stability of these phases and shift the corresponding transition points. The distribution of anisotropic NPs in block copolymers has recently been studied theoretically by the authors [36,37] assuming fixed phase-separated structures of the lamellae and hexagonal phases. Similarly to the molecular theory of nematic liquid crystals in the external field, the orientational order of NPs in this case is induced by the anisotropic mean-field created by the interaction between the NPs and the monomers of the two different blocks.…”