Phase behavior of rigid, amphiphilic star polymers

Koch, Christian; Panagiotopoulos, Athanassios Z.; Verso, Federica Lo; Likos, Christos N.

doi:10.1039/c3sm51135a

Cited by 12 publications

(24 citation statements)

References 71 publications

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“…This estimate is important because it shows that the tension ratio o is generally not very different from unity, which in turn implies that by a suitable choice of endgroups both the attractive o o 1 and the repulsive o 4 1 regimes are achievable. Such a conclusion is consistent with experiments reporting aggregation in end-functionalized star and brushes [41][42][43] as well as stable, non-aggregated dispersions of stars based on homopolymers, thereby proving that by a suitable modification of endgroups one may control o. In addition, eqn (15) shows that the range of model parameters scanned in this paper does include most of the experimentally relevant cases.…”

Section: Theoretical Estimates Of Reduced Egelstaff-widom Length W Ansupporting

confidence: 89%

Structure formation in soft nanocolloids: liquid-drop model

2018

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Using a model where soft nanocolloids such as spherical polymer brushes and star polymers are viewed as compressible liquid drops, we theoretically explore contact interactions between such particles. By numerically minimizing the phenomenological free energy consisting of bulk and surface terms, we find that at small deformations the drop-drop interaction is pairwise additive and described by a power law. We also propose a theory to describe the small-deformation regime, and the agreement is very good at all drop compressibilities. The large-deformation regime, which is dominated by many-body interactions, is marked by a rich phase diagram which includes the face- and body-centered-cubic, σ, A15, and simple hexagonal lattice as well as isostructural and re-entrant transitions. Most of these features are directly related to the non-convex deformation free energy emerging from many-body effects in the partial-faceting regime. The phase diagram, which depends on just two model parameters, contains many of the condensed phases observed in experiments. We also provide statistical-mechanical arguments that relate the two model parameters to the molecular architecture of the polymeric nanocolloids, chain rigidity, and solvent quality. The model represents a generic framework for the overarching features of the phase behavior of polymeric nanocolloids at high compressions.

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Section: Theoretical Estimates Of Reduced Egelstaff-widom Length W Ansupporting

confidence: 89%

Structure formation in soft nanocolloids: liquid-drop model

2018

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“…The inherent flexibility of such soft-particles leads to formation of ordered structures in the case of high functionality [33]. On the other hand, low-functionally TSPs tend to form micellar aggregates [34][35][36][37], which at relatively high concentrations self-assemble into long worm-like micelles [35,38]. In previous work, we have examined the effects of temperature (or attraction strength) on the self-assembly of these low-f TSPs in dilute solution [32].…”

Section: Introductionmentioning

confidence: 99%

The influence of arm composition on the self-assembly of low-functionality telechelic star polymers in dilute solutions

et al. 2020

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We combine synthesis, physical experiments, and computer simulations to investigate self-assembly patterns of low-functionality telechelic star polymers (TSPs) in dilute solutions. In particular, in this work, we focus on the effect of the arm composition and length on the static and dynamic properties of TSPs, whose terminal blocks are subject to worsening solvent quality upon reducing the temperature. We find two populations, single stars and clusters, that emerge upon worsening the solvent quality of the outer block. For both types of populations, their spatial extent decreases with temperature, with the specific details (such as temperature at which the minimal size is reached) depending on the coupling between inter- and intra-molecular associations as well as their strength. The experimental results are in very good qualitative agreement with coarse-grained simulations, which offer insights into the mechanism of thermoresponsive behavior of this class of materials.

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“…Moreover, star molecules bridge the gap between linear polymers and colloids 54,55 and can present interesting (colloidal-like) ordering effects, sometime enhanced due to their softer character. 53,[56][57][58][59] In this context, a suggesting observation in these simulations is the onset of some ordering in the neutral direction at large shear rates whose origin (hydrodynamic or entropic) remains to be established.…”

Section: Introductionmentioning

confidence: 99%

Open boundary molecular dynamics of sheared star-polymer melts

2016

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Open boundary molecular dynamics (OBMD) simulations of a sheared star polymer melt under isothermal conditions are performed to study the rheology and molecular structure of the melt under a fixed normal load. Comparison is made with the standard molecular dynamics (MD) in periodic (closed) boxes at a fixed shear rate (using the SLLOD dynamics). The OBMD system exchanges mass and momentum with adjacent reservoirs (buffers) where the external pressure tensor is imposed. Insertion of molecules in the buffers is made feasible by implementing there a low resolution model (blob-molecules with soft effective interactions) and then using the adaptive resolution scheme (AdResS) to connect with the bulk MD. Straining with increasing shear stress induces melt expansion and a significantly different redistribution of pressure compared with the closed case. In the open sample, the shear viscosity is also a bit lowered but more stable against the viscous heating. At a given Weissenberg number, molecular deformations and material properties (recoverable shear strain and normal stress ratio) are found to be similar in both setups. We also study the modelling effect of normal and tangential friction between monomers implemented in a dissipative particle dynamics (DPD) thermostat. Interestingly, the tangential friction substantially enhances the elastic response of the melt due to a reduction of the kinetic stress viscous contribution.

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Phase behavior of rigid, amphiphilic star polymers

Cited by 12 publications

References 71 publications

Structure formation in soft nanocolloids: liquid-drop model

Structure formation in soft nanocolloids: liquid-drop model

The influence of arm composition on the self-assembly of low-functionality telechelic star polymers in dilute solutions

Open boundary molecular dynamics of sheared star-polymer melts

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