arXiv subjects

Remco Tuinier

Publications and source records attributed to Remco Tuinier.

13 recordsLinked to original sources

arXiv2025

Associative and Segregative Liquid-Liquid Phase Separation in Macromolecular Solutions

We investigate liquid-liquid phase separation (LLPS) and interfacial properties of two LLPS modes: associative (ALLPS) and segregative (SLLPS). Analytical expressions for the critical point (CP) and binodal boundaries are derived and show excellent agreement with self-consistent field (SCF) lattice computations. Distinct thermodynamic features differentiate ALLPS from SLLPS: (1) in ALLPS, polymers co-concentrate within a single dense phase coexisting with a solvent-rich phase, whereas in SLLPS each polymer forms a separate phase; (2) the attractive interaction per monomer in ALLPS is strongly dependent on solvent quality, but solvent-independent in SLLPS; and (3) ALLPS binodals exhibit near-universal behavior, largely independent of solvent content. SCF results further show that interfacial tension increases and interfacial width decreases with distance from the CP. We provide scaling relations for both quantities are provided. Compared with SLLPS, ALLPS displays higher interfacial tension and a thinner interface, reflecting distinct molecular organization at the liquid-liquid boundary.

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arXiv2025

Thermodynamics of Hard Sphere and Spherocylinder Mixtures -- Scaled Particle Theory and Monte Carlo Simulations

We review the literature on scaled particle theory (SPT) and its extensions and discuss results applied to describe the thermodynamics of hard particle mixtures. After explaining the basic concepts of scaled particle theory to compute the free energy of immersing a particle into a mixture, examples are discussed for the simple case of a hard sphere dispersion and the free volume fraction of ghost spheres in a hard sphere dispersion. Next, the concept is applied to mixtures, and general expressions are shown that relate the free volume fraction in mixtures to the key thermodynamic properties, such as the chemical potential(s) and (osmotic) pressure. Subsequently, it is revealed how these concepts can be extended towards multi-component systems. It is shown that free volume fractions provide chemical potentials and total pressure of multi-component mixtures, and thereby yield the full equation of state. We present novel results for ternary particle dispersions composed of hard spherocylinders and two types of hard spheres differing in size. Throughout, we show the accuracy of SPT by comparing the results with those of Monte Carlo computer simulations.

cond-mat.soft↗

arXiv2023

Equation of State of Charged Rod Dispersions

We study the accuracy of the theory of Stroobants, Lekkerkerker and Odijk, called SLO theory (Macromolecules 19 (1986) 2232-2238), to describe the thermodynamic properties of an isotropic fluid of charged rods. By incorporation of the effective diameter of the rods according to SLO theory into scaled particle theory (SPT) we obtain an expression for the rod concentration-dependent free volume fraction and the osmotic pressure of a collection of charged hard spherocylinders. The results are compared to Monte Carlo simulations. We find close agreement between the simulation results and the SLO-SPT predictions for not too large values of the Debye length and for high rod charge densities. The deviations increase with rod density, particularly at concentrations above which isotropic-nematic phase transitions are expected.

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arXiv2021

Repulsive and attractive depletion forces mediated by nonadsorbing polyelectrolytes in the Donnan limit

In mixtures of colloids and nonadsorbing polyelectrolytes, a Donnan potential arises across the region between surfaces that are depleted of polyelectrolyte and the rest of the system. This Donnan potential tends to shift the polyelectrolyte density profile towards the colloidal surface and leads to local accumulation of polyelectrolytes. We derive a zero-field theory for the disjoining pressure between two parallel flat plates. Polyelectrolyte is allowed to enter the confined interplate region at the cost of a conformational free energy penalty. The resulting disjoining pressure shows a crossover to a repulsive regime when the interplate separation gets smaller than the size of the polyelectrolyte chain, followed by an attractive part. We find a quantitative match between the model and self-consistent field computations that take into account the full Poisson-Boltzmann electrostatics.

cond-mat.soft↗

arXiv2020

Phase stability of dispersions of hollow silica nanocubes mediated by non-adsorbing polymers

Although there are theoretical predictions [\textit{Eur.~Phys.~J.~E} \textbf{41} (2018) 110] for the rich phase behaviour of colloidal cubes mixed with non-adsorbing polymers, a thorough verification of this phase behaviour is still underway; experimental studies on mixtures of cubes and non-adsorbing polymers in bulk are scarce. In this paper, mixtures of hollow silica nanocubes and linear polystyrene in \textit{N,-N-}dimethylformamide are used to measure the structure factor of the colloidal cubes as a function of non-adsorbing polymer concentration. Together with visual observations these structure factors enabled us to assess the depletion-mediated phase stability of cube-polymer mixtures. The theoretical and experimental phase boundaries for cube-depletant mixtures are in remarkable agreement, despite the simplifications underlying the theory employed.

cond-mat.soft↗

arXiv2019

Experimental Evidence for Algebraic Double-Layer Forces

According to conventional wisdom electric double-layer forces normally decay exponentially with separation distance. Here we present experimental evidence of algebraically decaying double-layer interactions. We show that algebraic interactions arise in both strongly overlapping as well as counterion-only regimes, albeit the evidence is less clear for the former regime. In both of these cases the disjoining pressure profile assumes an inverse square distance dependence. At small separation distances another algebraic regime is recovered. In this regime the pressure decays as the inverse of separation distance.

cond-mat.soft↗

arXiv2018

Depletion-driven four-phase coexistences in discotic systems

Free volume theory (FVT) is a versatile and tractable framework to predict the phase behaviour of mixtures of platelets and non-adsorbing polymer chains in a common solvent. Within FVT, three principal reference phases for the hard platelets are considered: isotropic (I), nematic (N), and columnar (C). We derive analytical expressions that enable us to systematically trace the different types of phase coexistences revealed upon adding depletants and confirm the predictive power of FVT by testing the calculated diagrams against phase stability scenarios from computer simulation. A wide range of \textit{multi}-phase equilibria is revealed, involving two-phase isostructural transitions of all phase symmetries (INC) considered as well as the possible three-phase coexistences. Moreover, we identify the system parameters, relative disk shapes and colloid-polymer size ratios, at which four-phase equilibria are expected. These involve a remarkable coexistence of all three phase states commonly encountered in discotics including isostructural coexistences I$_1$-I$_2$-N-C, I-N$_1$-N$_2$-C, and I-N-C$_1$-C$_2$.

cond-mat.soft↗

arXiv2014

Stochastic Interactions of Two Brownian Hard Spheres in the Presence of Depletants

A quantitative analysis is presented for the stochastic interactions of a pair of Brownian hard spheres in non-adsorbing polymer solutions. The hard spheres are hypothetically trapped by optical tweezers and allowed for random motion near the trapped positions. The investigation focuses on the long-time correlated Brownian motion. The mobility tensor altered by the polymer depletion effect is computed by the boundary integral method, and the corresponding random displacement is determined by the fluctuation-dissipation theorem. From our computations it follows that the presence of depletion layers around the hard spheres has a significant effect on the hydrodynamic interactions and particle dynamics as compared to pure solvent and pure polymer solution (no depletion) cases. The probability distribution functions of random walks of the two interacting hard spheres that are trapped clearly shifts due to the polymer depletion effect. The results show that the reduction of the viscosity in the depletion layers around the spheres and the entropic force due to the overlapping of depletion zones have a significant influence on the correlated Brownian interactions.

cond-mat.soft↗

arXiv2013

Self-consistent field predictions for quenched spherical biocompatible triblock copolymer micelles

We have used the Scheutjens-Fleer self-consistent field (SF-SCF) method to predict the self-assembly of triblock copolymers with a solvophilic middle block and sufficiently long solvophobic outer blocks. We model copolymers consisting of polyethylene oxide (PEO) as solvophilic block and poly(lactic-co-glycolic) acid (PLGA) or poly({\ko}-caprolactone) (PCL) as solvophobic block. These copolymers form structurally quenched spherical micelles provided the solvophilic block is long enough. Predictions are calibrated on experimental data for micelles composed of PCL-PEO-PCL and PLGA-PEO-PLGA triblock copolymers prepared via the nanoprecipitation method. We establish effective interaction parameters that enable us to predict various micelle properties such as the hydrodynamic size, the aggregation number and the loading capacity of the micelles for hydrophobic species that are consistent with experimental finding.

cond-mat.soft↗

arXiv2012

How Flow Changes Polymer Depletion in a Slit

A theoretical model is developed for predicting dynamic polymer depletion effects under the influence of fluid flow. The results are established by combining the two-fluid model and the self-consistent field theory. We consider a uniform fluid flow across a slit containing a solution with polymer chains. The two parallel and infinitely long walls are permeable to solvent only and the polymers do not adsorb to these walls. For a weak flow and a narrow slit in Theta-solvent conditions, an analytic expression is derived to describe the steady state polymer concentration profiles. In both Theta- and good-solvents, we compute the time evolution of the concentration profiles for various flow rates characterized by the Peclet number. The model reveals the interplay of depletion, solvent condition, slit width, and relative strength of the fluid flow.

cond-mat.soft↗

arXiv2011

Phase stability of a reversible supramolecular polymer solution mixed with nanospheres

Theory is presented for the phase stability of mixtures containing nanospheres and non-adsorbing reversible supramolecular polymers. This was made possible by incorporating the depletion thickness and osmotic pressure of reversible supramolecular polymer chains into generalized free-volume theory, recently developed for investigating the phase behaviour of colloidal spheres mixed with interacting polymers [Adv. Colloid Interface Sci. 143 (2008) 1-47]. It follows that the fluidfluid phase stability region where reversible supramolecular polymer chains can be mixed with nanospheres is sensitive to the energy of scission between the monomers and to the nanoparticle radius. One can then expect the fluidfluid coexistence curves to have a strong dependence on temperature and that shifting of phase boundaries within a single experimental system should be possible by varying the temperature. The calculations reveal the width of the stability region to be rather small. This implies that phase homogeneity of product formulations containing reversible supramolecular polymers is only possible at low nanoparticle concentrations.

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arXiv2009

A simple patchy colloid model for the phase behavior of lysozyme dispersions

We propose a minimal model for spherical proteins with aeolotopic pair interactions to describe the equilibrium phase behavior of lysozyme. The repulsive screened Coulomb interactions between the particles are taken into account assuming that the net charges are smeared out homogeneously over the spherical protein surfaces. We incorporate attractive surface patches, with the interactions between patches on different spheres modeled by an attractive Yukawa potential. The parameters entering the attractive Yukawa potential part are determined using information on the experimentally accessed gas-liquid-like critical point. The Helmholtz free energy of the fluid and solid phases is calculated using second-order thermodynamic perturbation theory. Our predictions for the solubility curve are in fair agreement with experimental data. In addition, we present new experimental data for the gas-liquid coexistence curves at various salt concentrations and compare these with our model calculations. In agreement with earlier findings, we observe that the strength and the range of the attractive potential part only weakly depend on the salt content.

cond-mat.soft↗

arXiv2005

Phase behaviour of charged colloidal sphere dispersions with added polymer chains

We study the stability of mixtures of highly screened repulsive charged spheres and non-adsorbing ideal polymer chains in a common solvent using free volume theory. The effective interaction between charged colloids in an aqueous salt solution is described by a screened-Coulomb pair potential, which supplements the pure hard-sphere interaction. The ideal polymer chains are treated as spheres that are excluded from the colloids by a hard-core interaction, whereas the interaction between two ideal chains is set to zero. In addition, we investigate the phase behaviour of charged colloid-polymer mixtures in computer simulations, using the two-body (Asakura-Oosawa pair potential) approximation to the effective one-component Hamiltonian of the charged colloids. Both our results obtained from simulations and from free volume theory show similar trends. We find that the screened-Coulomb repulsion counteracts the effect of the effective polymer-mediated attraction. For mixtures of small polymers and relatively large charged colloidal spheres, the fluid-crystal transition shifts to significantly larger polymer concentrations with increasing range of the screened-Coulomb repulsion. For relatively large polymers, the effect of the screened-Coulomb repulsion is weaker. The resulting fluid-fluid binodal is only slightly shifted towards larger polymer concentrations upon increasing the range of the screened-Coulomb repulsion. In conclusion, our results show that the miscibility of dispersions containing charged colloids and neutral non-adsorbing polymers increases, upon increasing the range of the screened-Coulomb repulsion, or upon lowering the salt concentration, especially when the polymers are small compared to the colloids.

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