Effect of excluded volume interactions on the interfacial properties of colloid-polymer mixtures

Fortini, Andrea; Bolhuis, Peter G.; Dijkstra, Marjolein

doi:10.1063/1.2818562

Cited by 24 publications

(17 citation statements)

References 63 publications

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“…22-25 discuss phenomenological generalizations of the AOV model, while Refs. 14,26-29 discuss coarse-grained models in which the polymer-colloid and polymer-polymer potentials are derived either numerically 14,26 from fullmonomer simulations or by means of general theoretical considerations. [27][28][29] Another successfull approach is freevolume theory 10 which has been originally developed for mixtures of colloids and ideal polymers and later generalized to include polymer-polymer and polymer-colloid interactions.…”

Section: Introductionmentioning

confidence: 99%

Phase diagram of mixtures of colloids and polymers in the thermal crossover from good to θ solvent

D’Adamo

Pelissetto

Pierleoni

2014

The Journal of Chemical Physics

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We determine the phase diagram of mixtures of spherical colloids and neutral nonadsorbing polymers in the thermal crossover region between the θ point and the good-solvent regime. We use the generalized free-volume theory (GFVT), which turns out to be quite accurate as long as q = Rg/Rc ∼ < 1 (Rg is the radius of gyration of the polymer and Rc is the colloid radius). Close to the θ point the phase diagram is not very sensitive to solvent quality, while, close to the good-solvent region, changes of the solvent quality modify significantly the position of the critical point and of the binodals. We also analyze the phase behavior of aqueous solutions of charged colloids and polymers, using the extension of GFVT proposed by Fortini et al., J. Chem. Phys. 128, 024904 (2008).

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Section: Introductionmentioning

confidence: 99%

Phase diagram of mixtures of colloids and polymers in the thermal crossover from good to θ solvent

D’Adamo

Pelissetto

Pierleoni

2014

The Journal of Chemical Physics

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“…From recent MC simulations by Fortini et al [91], which authors use the same method as Bolhuis et al [87], we can deduce the free volume fraction as the ratio ϕ/φ or y i /y (see Fig. 7a,b in [91]) for a size ratio q R = 1.05. These simulation results are plotted in Fig.…”

Section: Free Volume Fractionmentioning

confidence: 99%

Analytical phase diagrams for colloids and non-adsorbing polymer

Fleer

Tuinier

2008

Advances in Colloid and Interface Science

116

201

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We review the free-volume theory (FVT) of Lekkerkerker et al. [Europhys. Lett. 20 (1992) 559] for the phase behavior of colloids in the presence of non-adsorbing polymer and we extend this theory in several aspects:(i) We take the solvent into account as a separate component and show that the natural thermodynamic parameter for the polymer properties is the insertion work Πv, where Π is the osmotic pressure of the (external) polymer solution and v the volume of a colloid particle. (ii) Curvature effects are included along the lines of Aarts et al. [J. Phys.: Condens. Matt. 14 (2002) 7551] but we find accurate simple power laws which simplify the mathematical procedure considerably. (iii) We find analytical forms for the first, second, and third derivatives of the grand potential, needed for the calculation of the colloid chemical potential, the pressure, gas-liquid critical points and the critical endpoint (cep), where the (stable) critical line ends and then coincides with the triple point. This cep determines the boundary condition for a stable liquid.We first apply these modifications to the so-called colloid limit, where the size ratio q R = R/a between the radius of gyration R of the polymer and the particle radius a is small. In this limit the binodal polymer concentrations are below overlap: the depletion thickness δ is nearly equal to R, and Π can be approximated by the ideal (van 't Hoff) law Π = Π 0 = φ/N, where φ is the polymer volume fraction and N the number of segments per chain. The results are close to those of the original Lekkerkerker theory. However, our analysis enables very simple analytical expressions for the polymer and colloid concentrations in the critical and triple points and along the binodals as a function of q R . Also the position of the cep is found analytically. In order to make the model applicable to higher size ratio's q R (including the so-called protein limit where q R N 1) further extensions are needed. We introduce the size ratio q = δ/a, where the depletion thickness δ is no longer of order R. In the protein limit the binodal concentrations are above overlap. In such semidilute solutions δ ≈ ξ, where the De Gennes blob size (correlation length) ξ scales as ξ ∼ φ − γ , with γ = 0.77 for good solvents and γ = 1 for a theta solvent. In this limit Π = Π sd ∼ φ 3γ . We now apply the following additional modifications:(iv) Π = Π 0 + Π sd , where Π sd =Aφ 3γ ; the prefactor A is known from renormalization group theory. This simple additivity describes the crossover for the osmotic pressure from the dilute limit to the semidilute limit excellently. (v) δ − 2 = δ 0 − 2 + ξ − 2 , where δ 0 ≈ R is the dilute limit for the depletion thickness δ. This equation describes the crossover in length scales from δ 0 (dilute) to ξ (semidilute).With these latter two modifications we obtain again a fully analytical model with simple equations for critical and triple points as a function of q R . In the protein limit the binodal polymer concentrations scale as q R 1/γ , and phase diagrams φq ...

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“…8,[15][16][17][18] Athermal linear homopolymers are common well-studied depletants. 13,[19][20][21][22][23] However, additional factors can be adjusted to ne tune the behavior of such a depletant. For instance, the importance of attractive interactions between the polymer and colloids is of particular interest since in many experimental situations some amount of attraction between the polymer and colloids is expected due to dispersion forces.…”

Section: Introductionmentioning

confidence: 99%

Relative stability of the FCC and HCP polymorphs with interacting polymers

2015

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Recent work [Mahynski et al., Nat. Commun., 2014, 5, 4472] has demonstrated that the addition of long linear homopolymers thermodynamically biases crystallizing hard-sphere colloids to produce the hexagonal close-packed (HCP) polymorph over the closely related face-centered cubic (FCC) structure when the polymers and colloids are purely repulsive. In this report, we investigate the effects of thermal interactions on each crystal polymorph to explore the possibility of stabilizing the FCC crystal structure over the HCP. We find that the HCP polymorph remains at least as stable as its FCC counterpart across the entire range of interactions we explored, where interactions were quantified by the reduced second virial coefficient, -1.50 < B < 1.01. This metric conveniently characterizes the crossover from entropically to energetically dominated systems at B ≈ 0. While the HCP relies on its octahedral void arrangement for enhanced stability when B > 0, its tetrahedral voids produce a similar effect when B < 0 (i.e. when energetics dominate). Starting from this, we derive a mean-field expression for the free energy of an infinitely-dilute polymer adsorbed in the crystal phase for nonzero B. Our results reveal that co-solute biasing of a single polymorph can still be observed in experimentally realizable scenarios when the colloids and polymers have attractive interactions, and provide a possible explanation for the experimental finding that pure FCC crystals are elusive in these binary mixtures.

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Effect of excluded volume interactions on the interfacial properties of colloid-polymer mixtures

Cited by 24 publications

References 63 publications

Phase diagram of mixtures of colloids and polymers in the thermal crossover from good to θ solvent

Phase diagram of mixtures of colloids and polymers in the thermal crossover from good to θ solvent

Analytical phase diagrams for colloids and non-adsorbing polymer

Relative stability of the FCC and HCP polymorphs with interacting polymers

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