Phase Diagrams of Self-Assembled Mono-Tethered Nanospheres from Molecular Simulation and Comparison to Surfactants

Abstract

We perform Brownian dynamics simulations on model 3-D systems of mono-tethered nanospheres (TNS) to study the equilibrium morphologies formed by their self-assembly in a selective solvent. We predict that in contrast to flexible amphiphiles the nanospheres are locally ordered and there is an increase in the local order with an increase in concentration or relative nanoparticle diameter. We present the temperature vs concentration phase diagram for a system of TNS and propose a dimensionless scaling factor F(v) (headgroup volume/tether volume) that allows a comparison between the morphologies formed from TNS and traditional surfactants.

Rational design of nanomaterials from assembly and reconfigurability of polymer-tethered nanoparticles

“…[14] Key amongst these findings was the realization that the phase behavior of tethered NPs, to a great extent, is consistent with that of surfactants and liquid crystals. [11] Recently, many of these initial findings have also been corroborated with experiments. [31] Given the close relationship between tethered NPs and liquid crystals, [58] the roles of the shape of the NP head group have also been extensively investigated.…”

“…Initial investigations focused on establishing relationships between existing theory for polymers and surfactants, and TNPs via simulation. [11,58] Toward this end, the focus has been on the phase behavior [10,11,15,57,59] and properties [60][61][62][63][64] of TNPs, as a function of the size of the isotropic NPs. Figure 4 shows examples of interesting assembled structures from our studies, including double gyroids, [17] cylinders and columnar structures, [65] bilayer sheets, [66] and dodecagonal quasicrystals.…”

“…Moreover, TNPs create a spectrum of mesoscopic assemblies, including: (1) pseudo-two-dimensional (2D) assemblies (e.g. lamellae), [11][12][13] (2) micellar structures adopting body-centered cubic (BCC), Frank-Kasper, quasiscrystalline patterns, [14] and (3) complex gyroid, [15] diamond, [16] or other networks. [17] With such a wide range of assembly behavior, an enormous design space is accessible for the design and discovery of new materials.…”

Derivation of coarse-grained potentials via multistate iterative Boltzmann inversion

“…This is of particular importance when studying the self-assembly of soft matter systems, where the assembly is typically driven by weak forces (e.g., hydrophobicity and entropy) [1][2][3][4][5][6] and structures often demonstrate hierarchical ordering (e.g., molecules organized into micelles, micelles organized into local/global patterns). 5,[7][8][9][10][11] While generic, non-specific CG models have been widely applied, [12][13][14][15][16] providing important information regarding trends and design rules, it is often necessary to use CG models specifically mapped to the system of interest to provide a direct one-to-one correspondence with experiment. While several "transferable" CG forcefields, such as TraPPE-CG 17 and MARTINI, 18 have been developed, akin to forcefield development at the atomistic level, [19][20][21][22][23] the development of new CG forcefields is still often necessary.…”

Kinetics of hexagonal cylinders to face-centered cubic spheres transition of triblock copolymer in selective solvent: Brownian dynamics simulation

“…Thus compared to all atom molecular dynamics, BD is more efficient and saves computational time in simulating the polymer solution system. For example, BD methods have been used for simulating polymer flow, 16 phase diagram in surfactants modeled as sphere tethered to a chain 15,17 and in block copolymer melts, 14 solution, 18 and polymer brushes systems. 11,19 To the best of our knowledge, BD simulation has not been reported to study the kinetics of the HEX cylinders to FCC or BCC spheres transition for block copolymer in a selective solvent system.…”