Cascade of Transitions of Polyelectrolytes in Poor Solvents

Dobrynin, Andrey V.; Rubinstein, Michael; Obukhov, Sergei

doi:10.1021/ma9507958

Cited by 450 publications

(597 citation statements)

References 15 publications

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“…One last point that should be made about the Rayleigh instability for charged droplets is that it exists in a small part of the phase diagram. This was shown theoretically in the original works by Dobrynin et al 26 and in this study we have found if we change a parameter such as v or charge fraction appreciably (from the values we selected) then we can completely bypass the Rayleigh instability.…”

Section: Condensate Shapessupporting

confidence: 75%

“…This is a relatively good assumption at low charge fractions, but as the charge fraction increases it is well known counterions will condense on the charged globule. 26,37 There are number of possible effects which may now come in play. For example, the counterions can now screen the long range Coulomb repulsion and effectively renormalize the length scale of this repulsion.…”

Section: Condensate Shapesmentioning

confidence: 99%

“…Over the last decade or so, it has been recognized an elongated polymer droplet must also be unstable to capillary wavelength fluctuations. However, due to the chain's connectivity the complete fissioning of the droplet cannot occur [24][25][26] and instead novel shapes such as a ball and chain conformation 24 or a pearl-necklace 25,26 conformation may evolve. Although numerous experiments point to the validity of these models in bulk solutions, that is, in three-dimensions, often experiments will involve a substrate on which the polymer (liquid) droplet will adsorb, for example, atomic force microscopy or surface force apparatus.…”

Section: Introductionmentioning

confidence: 99%

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Shape instabilities in adsorbed polymer condensates

Pereira

Pattanayek

2007

J Polym Sci B Polym Phys

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A polymer chain in a poor solvent collapses to a spherical globule. If this globule is subsequently deformed, either by stretching it or if it has some non-zero net electric charge, it will become unstable to sinusoidal perturbations leading to novel final states. When such globules are imaged by direct methods such as atomic force microscopy the substrate on which they adsorb can affect the final morphological state. We therefore investigate strongly adsorbed polymers in poor solvents. We demonstrate that the real-space, Self-Consistent Field method is an ideal numerical tool in predicting equilibrium morphologies. New structures are predicted, which support previous explicit free energy calculations.

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Section: Condensate Shapessupporting

confidence: 75%

Section: Condensate Shapesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Shape instabilities in adsorbed polymer condensates

Pereira

Pattanayek

2007

J Polym Sci B Polym Phys

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“…Optimizing the total energy we ÿnd: h∼Q. This picture has been independently conÿrmed by MC simulations [22] of homogeneous weakly charged polymers. Since such polymers do not condense into globular shape, and attractive short-range interaction has been added to ensure the condensation.…”

mentioning

confidence: 79%

Necklace model of randomly charged polymers

Kantor¹,

Kardar²,

Ertaş³

1998

Physica A: Statistical Mechanics and its Applications

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Spatial conformations of randomly charged polymers (polyampholytes (PAs)) strongly depend on their total (excess) charge Q. For Q larger (smaller) that some critical value the PA is expanded (collapsed). The transition between the collapsed and the expanded states is reminiscent of the Rayley shape instability of a charged drop. The expanded states can be approximately described using the necklace model, as a chain of interconnected compact globules. Randomness of the charge sequence along the chain modiÿes the simple model creating wide distribution of sizes of the "beads" of the necklace. A simple mathematical model was proposed to describe the shape of the necklace. ? 1998 Elsevier Science B.V. All rights reserved. The importance of understanding proteins [1] has attracted much attention to the statistical mechanics of heterogeneous polymers. A particular type of heteropolymers built with a mixture of positively and negatively charged groups along their backbone are called polyampholytes (PAs). Proteins are biomolecules formed from amino-acids. Out of 20 natural amino-acids, three are positively charged (Lys, Arg, His) and two are negatively charged (Asp, Glu) [2]. A statistical study of the charge distribution along the sequences of biomolecules [3] indicates that from the point of view of electrostatic interactions the charge sequences in proteins are only weakly (anti-)correlated. Thus, the proteins can be approximately treated as randomly charged PAs. Experiments on PAs and polyamphilic gels [ 4 -8] reveal an extreme sensitivity of their geometric properties on their overall charge. We will show that the presence of long-range electrostatic interactions indeed causes a rather unique behavior in such polymers: the spatial conformations of a single PA with unscreened electrostatic interactions at a low temperature T strongly depend on its total (excess) charge Q. We will demonstrate that the geometry of the system can be qualitatively described using simple models. PACS

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“…

In a recent paper, Dobrynin et al 1 concluded that a polyelectrolyte can assume in a poor solvent a "necklace configuration" in which globular clusters are linked by flexible chain segments. In the introductory paragraph they write "water, a poor solvent for many polymers ... causes chains without charged groups to collapse into spherical globules".

…”

mentioning

confidence: 99%

Temperature Effects on the Living Cationic Polymerization of Isobutylene: Determination of Spontaneous Chain Transfer Constants in the Presence of Terminative Chain Transfer Volume 31, Number 14, July 14, 1998, p 4439

Fodor¹,

Bae²,

Faust³

1998

Macromolecules

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In a recent paper, Dobrynin et al. 1 concluded that a polyelectrolyte can assume in a poor solvent a "necklace configuration" in which globular clusters are linked by flexible chain segments. In the introductory paragraph they write "water, a poor solvent for many polymers ... causes chains without charged groups to collapse into spherical globules". This implies that the analysis with which the paper is concerned is meant to apply to polyelectrolytes such as poly(styrenesulfonic acid), where the ionic functions are attached to a hydrophobic backbone.The model used for the calculations consists of a freely jointed uniformly charged chain, but nowhere do the authors refer to the mutual attraction of ion pairs, which leads to a collapse of polyions at a critical charge density when the dielectric constant of the medium is sufficiently reduced below that of water. This effect has been demonstrated for poly(acrylic acid) and poly-(methacrylic acid) in methanol where the solution viscosity first increases but then precipitously drops during the titration. 2,3 The collapse of polyelectrolyte gels under certain conditions when their charge density is increased has also been ascribed by Khokhlov and his collaborators 4 to ion-pair interactions. Similar effects are amply documented in studies of ionomer solutions. 5 In view of this deficiency in the analysis of Dobrynin et al., it remains an open question whether a uniform polymer chain can assume a necklace configuration. On the other hand, two systems are known where the adsorption or covalent attachment of aromatic moieties at wide spacings to a hydrophilic polymer leads in water solution to a local clustering of the chain around the hydrophobe. Such an effect was first described by Molyneux and Frank 6 for poly(N-vinylpyrrolidone), where it was shown that ten monomer residues are enclosing a variety of adsorbed aromatic additives. More recently, a similar effect was studied for poly-(methacrylic acid) (PMA), where cluster formation around adsorbed or covalently bound aromatic labels was demonstrated in aqueous solutions at low pH by changes in the fluorescent properties and the rotational diffusion of the label. 7,8 Such clustering of PMA around the atropisomeric binaphthyl has also been shown to lead to a change in the chemical behavior of the label. 9References and Notes

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Cascade of Transitions of Polyelectrolytes in Poor Solvents

Cited by 450 publications

References 15 publications

Shape instabilities in adsorbed polymer condensates

Shape instabilities in adsorbed polymer condensates

Necklace model of randomly charged polymers

Temperature Effects on the Living Cationic Polymerization of Isobutylene: Determination of Spontaneous Chain Transfer Constants in the Presence of Terminative Chain Transfer Volume 31, Number 14, July 14, 1998, p 4439

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