Hierarchical and synergistic self-assembly in composites of model wormlike micellar-polymers and nanoparticles results in nanostructures with diverse morphologies

Abstract

Using Monte carlo simulations, we investigate the self-assembly of model nanoparticles inside a matrix of model equilibrium polymers (or matrix of Wormlike micelles) as a function of the polymeric matrix density and the excluded volume parameter between polymers and nanoparticles. In this paper, we show morphological transitions in the system architecture via synergistic self-assembly of nanoparticles and the equilibrium polymers. In a synergistic self-assembly, the resulting morphology of the system is a result of the interaction between both nanoparticles and the polymers, unlike the polymer templating method. We report the morphological transition of nanoparticle aggregates from percolating network-like structures to non-percolating clusters as a result of the change in the excluded volume parameter between nanoparticles and polymeric chains. In parallel with the change in the self-assembled structures of nanoparticles, the matrix of equilibrium polymers also shows a transition from a dispersed state to a percolating network-like structure formed by the clusters of polymeric chains. We show that the shape anisotropy of the nanoparticle clusters formed is governed by the polymeric density resulting in rod-like, sheet-like or other anisotropic nanoclusters. It is also shown that the pore shape and the pore size of the porous network of nanoparticles can be changed by changing the minimum approaching distance between nanoparticles and polymers. We provide a theoretical understanding of why various nanostructures with very different morphologies are obtained.

Effect of size of nanoparticles on the Wormlike micelle-nanoparticle system

“…The percolating network-like structures of nanoparticles inside a wormlike micellar matrix is already reported experimentally [23]. The system also shows usniformly mixed state and non-percolating clusters of nanoparticles for lowest and high values of EVP [13]. In this paper we show that with increase in the size of nanoparticles, the value of EVP at which the morphological changes occurs gets shifted to the lower values.…”

“…As observed in Fig. 5(a), (and also established for all the micellar densities considered [13]) for all the values of σ n , the snapshots for the lowest possible values of σ 4n show a uniformly mixed state of micellar chains and NPs. From the figures 6(a), 7(a) and 8(a), it can be seen that NPs do not form clusters.…”

“…For small particles σ n = 1.5σ, it is already shown that the system forms a uniformly mixed state for the minimum possible value of σ 4n = 1.25σ ((σ 4n ) min = (σ + σ n )/2) [13]. Further increase in σ 4n leads to the formation of percolating network of NPs and polymeric chains.…”

“…This scheme of calculation of the effective volume of monomers is explained in Fig. 3 and also has been used in [13].…”

Defects and defect engineering in Soft Matter

“…403 Density and size of these filler aggregates depend on the individual interactions between the fillers as well as on the interaction between the fillers and the hosting network matrix. 388,404,405 This type of defect has been extensively studied, while apparently opposite influences on the mechanical properties have been reported in different studies. In a part of these studies, filler aggregation has been introduced to be responsible for the enhancement of the mechanical properties.…”