Predicting the Morphologies of Confined Copolymer/Nanoparticle Mixtures

Abstract

To isolate the factors that control the structure of nanocomposite thin films, we develop a computational model and scaling theory to investigate the behavior of diblock/nanoparticle mixtures that are confined between two hard walls. We find that in such restricted geometries a polymer-induced depletion attraction drives the particles to these walls. If the particles are chemically distinct from the walls, they will effectively modify the chemical nature of these substrates. This change in chemistry, in turn, affects the polymer−wall interactions and consequently the structure of the film. We illustrate this point by considering mixtures of particles and symmetric diblocks and show that the confining walls can be exploited to promote the self-assembly of the system into particle nanowires that extend throughout the films and are separated by nanoscale stripes of polymer domains. Such films constitute vital components in the fabrication of nanoscale devices. Furthermore, the results point to a novel technique for modifying the chemical nature of coatings and films entirely through self-assembly. Since this technique relies on entropic effects, it constitutes a fairly robust method that can be applied more generally than approaches that rely primarily on chemistry-specific enthalpic effects.

Responsive Assemblies: Gold Nanoparticles with Mixed Ligands in Microphase Separated Block Copolymers

“…[4][5][6][7][8][9][10][11][12] As an alternate method, besides the in-situ reduction technique, [13][14][15][16] the self-assembly of cadmium selenide, silica, gold and other nanoparticles into two-and three-dimensional ordered structures has been achieved recently, [5][6][7][8][9]11,12,17] led by the theoretical studies of Balazs and coworkers. [18][19][20] Kramer and coworkers [5][6][7][8] used polystyrene ligands to localize gold nanoparticles inside the polystyrene (PS) microdomains of a polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer, while mixtures of PS and P2VP ligands directed the nanoparticles to the interface between the PS and P2VP microdomains. Bockstaller, et al have shown that the location of particles within the same domain is affected by the size of the nanoparticle.…”

Modeling Polymers Containing Rod-Like Fillers: From Morphology to Mechanical Behavior

“…Our "CH/BD" model integrates a Cahn-Hilliard (CH) theory for binary blends with a Brownian dynamics (BD) simulation for nanoparticles to capture the structural evolution of the mixture (1,8,15). Our "SCF/DFT" combines a self-consistent field theory (SCFT) for diblock copolymers and density functional theory (DFT) for particles to generate the equilibrium morphology of the system (2)(3)(4)(5)7,9,(11)(12)(13)(14). The structural information that we obtained from the CH/BD and SCF/DFT studies was then used to compute the mechanical (1,5,8), electrical (1) or optical properties (2) of the composite.…”

Self‐Assembly of Nanoparticle–Copolymer Mixtures: A Kinetic Point of View

“…Recent theoretical arguments suggest that synergistic interactions between self-organizing particles and a self-assembling matrix material may lead to hierarchically ordered structures. [17][18][19] These predictions were recently confirmed in a study of a diblock copolymer having cylindrical microdomains with added nanoparticles. In this study a co-operative coupled interaction was found that led to hierarchically ordered structures upon thermal-or solvent-annealing where self-orienting, self-assembling arrays of microdomains were found without the use of external fields.…”