Order and Phase Behavior of Thin Film of Diblock Copolymer-Selective Nanoparticle Mixtures: A Molecular Dynamics Simulation Study

Abstract

By means of molecular dynamics simulations, we study AB diblock copolymer and nanoparticle mixtures confined between two identical walls in slit geometry. The nanoparticles are selective to the minority A-block, while the walls are neutral to both copolymer and nanoparticle. We obtained the various structures of the copolymer nanocomposites and are summarized in a phase diagram constructed in diblock composition and nanoparticle concentration space. In comparison to the phase diagram in bulk, we observe a much wider lamellar region with a broad class of lamellar structures, and the phase boundaries are shifted with increasing nanoparticle concentration. We find that both vertically and horizontally oriented lamellar structures are realized. The vertically oriented lamellae are formed by slightly asymmetric and symmetric diblock copolymers at low nanoparticle concentrations and have a very limited region of stability in the phase space, whereas the horizontally oriented lamellae are formed by asymmetric copolymer at large nanoparticle concentrations. In the vertically oriented lamellae, the segregated nanoparticles at the polymer−wall interfaces form nanoparticle monolayer above the A-domains and exclude A-monomers from this region. Consequently, the copolymer interface lines near walls are perturbed; also, the chains close to the walls are overstretched compared to the bulk. For horizontally oriented lamellae there is no overstretching of chains near the walls. The test of stability of the lamellar structures against the different thermodynamic pathways is also performed. Lastly, by considering the horizontal lamellae, we study the effect of nanoparticle concentration on the lamellar layer thickness.

A Review of Multiscale Computational Methods in Polymeric Materials

“…Still, the great power of MD is its proficiency to predict microstructure dynamics along its deterministic trajectory at an atomistic level. Applications of MD in the field of polymeric materials include topics such as macromolecular dynamics [ 119 , 120 , 121 , 122 , 123 , 124 ], intercalation phenomena in polymer/clay nanocomposites [ 63 ], structure of interfaces [ 125 , 126 , 127 ], polymer membranes [ 128 , 129 ], crystal structures [ 130 , 131 , 132 ], diffusion phenomena [ 133 , 134 , 135 , 136 ], segregation phenomena [ 137 ], tribological properties and crack propagation [ 138 , 139 , 140 ], thin films and surfaces [ 141 , 142 , 143 , 144 ], liquid crystalline polymers [ 145 , 146 ], rheology of polymeric systems [ 147 , 148 , 149 , 150 ], application of elongational flows on polymers using nonequilibrium MD [ 151 , 152 ], and the simulations of reactive systems such as crosslinking and decomposition of polymers using the ReaxFF force field [ 153 , 154 , 155 , 156 ].…”

Innovative Molecular Design for a Volume Oriented Component Diagnostic: Modified Magnetic Nanoparticles on High Performance Yarns for Smart Textiles

“…The diblock copolymers have a chemical asymmetry, f, which denotes the volume fraction of A monomers. [30] morphology close to non-selective substrates [26] while the pure copolymer melt tends to organize in perpendicular morphology. The phase diagram, which displays the morphological states of the composite is changed in two aspects by addition of a volume fraction, F p , of nanoparticles.…”

“…It has been shown that nanoparticles induce a parallel orientation of the lamellar copolymer figure. Here, g denotes the strength of preferred interaction between monomers and the walls, see ref. [30] morphology close to non-selective substrates [26] while the pure copolymer melt tends to organize in perpendicular morphology. [28][29][30] Moreover, nanoparticles segregate from the A phase to the substrate in slit-like geometries in order to optimize the free energy due to incommensurability effects, see left lower part of Figure 6.…”

“…Snapshots of the phase morphology and the resulting phase diagram are shown in Figure 6. [26] However, addition of nanoparticles is not merely equivalent to a change in composition of the block copolymer. Being mobile within the polymer phase nanoparticles interact specifically with phase boundaries and with hard surfaces in contact with the composite.…”

Phase Behavior of Copolymers Confined in Multi-Walled Nanotubes: Insights from Simulations

“…Two-dimensional (2D) confinement in the form of cylindrical pores with curved surfaces presents a more tightly confined geometry than that of thin films, and 2D confinements have been demonstrated to provide rich, varied structures. The use of cylindrical nanotubes produces 2D confinement with varying diameters for diblock copolymers as-studied in theory [16][17][18], simulation [19][20][21][22][23][24][25], and experiments [26][27][28][29][30][31]. Previous studies have also shown that the combined effects of confinement and curvature significantly influence the morphologies of copolymers in self-assembled systems.…”