Unfolding of a comb-like polymer in a poor solvent : Translation of macromolecular architecture in the force-deformation spectra
Polotsky, Alexey A. ; Birshtein, Tatiana M. ; Mercurieva, Anna A. ; Leermakers, Frans A.M. ; Borisov, Oleg V. - \ 2017
Soft Matter 13 (2017)48. - ISSN 1744-683X - p. 9147 - 9161.
A numerical self-consistent field modeling approach was employed to study the mechanical unfolding of a globule made by comb-like polymers in a poor solvent with the aim of unraveling how the macromolecular architecture affects the shape of the single-molecule force-deformation curves. We demonstrate that the dependence of the restoring force on the imposed extension of the main chain of the comb-like polymer exhibits a characteristic oscillatory shape in the intermediate deformation range. Theoretical arguments are developed that enable us to relate the shape of the patterns on the force-deformation curves to the molecular architecture (grafting density and length of the side chains) and interaction parameters. Thus, the results of our study suggest a new approach for the determination of macromolecular topology from single-molecule mechanical unfolding experiments.
Collapse of polyelectrolyte star. Theory and modelling
Rud, O.V. ; Mercurieva, A.A. ; Leermakers, F.A.M. ; Birshtein, T.M. - \ 2012
Macromolecules 45 (2012)4. - ISSN 0024-9297 - p. 2145 - 2160.
branched polyelectrolytes - homopolymer globule - copolymer micelles - block-copolymers - polymer brushes - conformations - layer - macromolecules - surfaces - solvent
The collapse of hydrophobic polyelectrolyte stars in aqueous solutions is studied using the Scheutjens–Fleer self-consistent field (SF-SCF) approach. The hydrophobic property of the segments tends to compact the stars, whereas the presence of charges has the opposite effect. As a result, star conformations can be switched from an extended, strongly hydrated, and swollen state to a collapsed state via semicollapsed, quasi-micellar state using control parameters such as the solvent quality, specified by the Flory–Huggins parameter, the pH value or the ionic strength. More specifically, there exists a range of parameters wherein the stars have an inhomogeneous radial structure with a collapsed region, referred to as the core, and a swollen region forming the corona. In such microphase segregated state the fraction of arms of the star that form the core, or alternatively escape into the swollen corona, can be controlled. The SF-SCF analysis is complemented with analytical models to rationalize the complex phase behavior.
Modeling of charged amphiphilic copolymer stars near hydrophobic surfaces
Mercurieva, A.A. ; Birshtein, T.M. ; Leermakers, F.A.M. - \ 2009
Langmuir 25 (2009)19. - ISSN 0743-7463 - p. 11516 - 11527.
poly(vinylidene fluoride) membranes - interacting chain molecules - branched polyelectrolytes - block-copolymers - protein resistance - statistical-theory - adsorption - polymers - hydrophilicity - micelles
Numerical self-consistent field theory has been applied to amphiphilic copolyelectrolyte stars in the solution and at interfaces both in one- and two-gradient coordinate systems. Our focus is on polymer stars for which the solvent is poor for the short blocks in the center and good for the longer charged chain parts at the periphery of the star. Both in solution as well as near an interface, the structure of the core is influenced by the hydrophobic interactions that tend to form a compact globule with size Rc and the forces exerted by the charged peripheral chain parts that like to expand the core. When the distance H of the center of the star to the surface becomes smaller than the total size R, the interaction force becomes significant; it is positive for Rc
Conformations of polymer and polyelectrolyte stars
Birshtein, T.M. ; Mercurieva, A.A. ; Leermakers, F.A.M. ; Rud, O.V. - \ 2008
Polymer Science Series. A: Polymer physics 50 (2008)9. - ISSN 0965-545X - p. 992 - 1007.
branched polyelectrolytes - starburst dendrimer - chain molecules - drug-delivery - field theory - model - nanoparticles - adsorption - micelles - dynamics
The structure of polymer and polyelectrolyte stars in solution was studied by means of joint analysis of the results of analytical consideration, allowing for nonlocal effects, and numerical simulation based on the Scheutjens-Fleer self-consistent field approach. A limitation of the theoretical treatment is the assumption that all ends of polymer chains are fixed onto the external surface and its benefit is the possibility of obtaining compact and interpretable results. The Scheutjens-Fleer approach makes it possible to study conformations without introduction of additional limitations. The combination of analytical methods and direct numerical calculation turns out to be especially informative.
Wetting phase diagrams of polyacid brush with a triple point.
Mercurieva, A.A. ; Iakovlev, P.A. ; Zhulina, E.B. ; Birshtein, T.M. ; Leermakers, F.A.M. - \ 2006
Physical Review. E, Statistical nonlinear, and soft matter physics 74 (2006)3. - ISSN 1539-3755 - 10 p.
interacting chain molecules - polymer brush - statistical-theory - adsorption - transitions - block - size
The (pre)wetting behavior of an annealed polyelectrolyte (PE) brush by an electrolyte solution that is strongly segregated from an apolar phase is analyzed. In this complex interface, there are interactions on various length scales. There are short-range interactions with the (uncharged) surface, and there are interactions on the length scale of the brush height. Using either the ionic strength or the water-surface interaction strength as the control parameters, it is possible to approach and induce a wetting transition in this system. The first-order wetting transition, promoted by favorable short-range substrate interactions with the surface, is in competition with the wetting transition controlled by the detachment of the fluid interface from the periphery of the PE brush. The electric double layer on top of the PE brush contributes with a repulsive forces to the disjoining pressure that tends to thicken the wetting film, and therefore, the transition in all cases is first order. Various phase portraits of the wetting phase diagram are envisioned. One of these features the crossing of two prewetting lines. At the crossing point three surface states coexist. This triple point is analyzed in some detail with the help of a molecular-level self-consistent field model
An annealed polyelectrolyte brush in a polar-nonpolar binary solvent : effect of pH and ionic strength
Mercurieva, A.A. ; Birshtein, T.M. ; Zhulina, E.B. ; Iakovlev, P. ; Male, J. van; Leermakers, F.A.M. - \ 2002
Macromolecules 35 (2002). - ISSN 0024-9297 - p. 4739 - 4752.
A weakly charged polyelectrolyte brush in a polar-nonpolar solvent mixture is studied using a boxlike model and by numerical self-consistent-field theory. The work is a continuation of a similar study of a neutral polymer brush in a solvent mixture with a pronounced solubility gap. We study both the structure and structural transitions of the brush in particular in the one-phase region of the solvent mixture in the bulk. With respect to the neutral system, the polyelectrolyte system is even richer in its behavior. Starting from a nonpolar main solvent, upon increasing the chemical potential of water, we find the development of a mesoscopic water film inside the brush. The polymer takes up this thin film as it finds an environment that allows for the dissociation of its groups energetically attractive. The phase transition can be accompanied by an anomalous collapse of the ionizable brush and tuned by the pH of the solution and the ionic strength in the system. Another brush transition can occur when nonpolar solvent is added to a brush immersed in water. Finally, it is feasible that systems exist that feature three successive brush transitions upon changing the bulk composition from pre-binodal, to biphasic, and then to post-binodal compositions, where a forward, a reentry, and again a forward transition are found, respectively.
Effect of a polymer brush on capillary condensation
Leermakers, F.A.M. ; Zhulina, E.B. ; Male, J. van; Mercurieva, A.A. ; Fleer, G.J. ; Birshtein, T.M. - \ 2001
Langmuir 17 (2001). - ISSN 0743-7463 - p. 4459 - 4466.
Amphiphilic polymer brush in a mixture of incompatible liquids. Numerical self-consistent-field calculations
Mercurieva, A.A. ; Leermakers, F.A.M. ; Birshtein, T.M. ; Fleer, G.J. ; Zhulina, E.B. - \ 2000
Macromolecules 33 (2000). - ISSN 0024-9297 - p. 1072 - 1081.
We studied a polymer brush composed of homodisperse end-grafted chains in a binary A-B solvent mixture by means of numerical self-consistent-field calculations. The focus is on the case that the solvents have a solubility gap in the bulk phase behavior, and we investigated the system near the bulk binodal. We assume that both solvents are good solvents for the polymer: the monomers of the chains have amphiphilic properties. When the minority solvent B is the better solvent, it is possible to find a preferential uptake of the solvent B. This solvent uptake can either occur in a continuous manner or in a first-order transition. From a wetting perspective, such a stepwise increase in B uptake may be identified as a prewetting step. In this case, however, the step is not necessarily caused by specific interactions with the solid substrate, but it results from an instability in the structure of the polymer brush at intermediate compositions of A and B in the brush. It is not always true that at coexistence the substrate is completely wet by the minority solvent, even when there is a prewetting step. We examine the post-transition solvent uptake up to and beyond the bulk binodal (in the case of partial wetting). The numerical SCF results complement a recent analysis of the same problem by a model of the Alexander-de Gennes type. Both in the numerical and in the analytical models, it is observed that the first-order phase transition is unusual: the polymer chains absorb the better solvent and then suddenly collapse to a very dense sublayer when there is only a small amount of the wetting component.
Wetting of a polymer brush, a system with pronounced critical wetting
Leermakers, F.A.M. ; Mercurieva, A. ; Male, J. van; Zhulina, E.B. ; Besseling, N.A.M. ; Birshtein, T.M. - \ 2000
Langmuir 16 (2000). - ISSN 0743-7463 - p. 7082 - 7087.
We consider a polymer brush composed of units of type P, at a solid substrate S in an incompatible binary A/L solvent mixture. At A/L coexistence the film thickness of the wetting component A depends mainly on the second virial coefficient AP of polymer-polymer contacts in an A-rich phase: with increasing AP the film thickness jumps from a microscopic to a mesoscopic value and then continues to grow proportionally to AP. The film grows smoothly without bounds when the fluid interface is further out than the segments of the brush chains can reach. This escape of the A-L interface from the brush coincides with the (second-order) wetting transition and occurs at . Substrates covered by a polymer brush are excellent surfaces to measure critical wetting because the wetting behavior can be tuned independently from the short-range interactions of the solvents with the solid substrate. For relatively thin brushes, van der Waals contributions can seriously modify these predictions. However, as the brush thickness is proportional to the chain length N, the relative contribution of these forces can be tuned; i.e., for a sufficiently large brush height the (long-range) van der Waals forces can be ignored. The wetting scenario has been elaborated by a numerical self-consistent-field theory for inhomogeneous polymer systems.