Dual polyelectrolyte-ionomer behavior of poly(acrylic acid) in methanol: 2. Salt solutions

Volkov, E. V.; Филиппова, О. Е.; Khokhlov, Alexei R.

doi:10.1007/s10595-005-0046-z

Cited by 5 publications

(8 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…methanol) under ionization [17][18][19] as well as counterion specificity in polyelectrolyte gel swelling and solution behavior 16,[19][20][21][22] are striking manifestations of ion association processes. The formation of ion pairs and multiplets was observed in computer simulations 23,24 and confirmed experimentally in luminescence 25,26 and conductivity 17,27,28 studies. Finally, theoretical approaches show that a considerable fraction of counterions binds with charges in chains even in semidilute solutions and swollen gels.…”

Section: Introductionsupporting

confidence: 66%

Two regions of microphase separation in ion-containing polymer solutions

Rumyantsev

Kramarenko

2017

Soft Matter

View full text Add to dashboard Cite

The phenomenon of spinodal decomposition in weakly charged polyelectrolyte solutions is studied theoretically within the random phase approximation. A novel feature of the theoretical approach is that it accounts for the effects of ionic association, i.e. ion pair and multiplet formation between counterions and ions in polymer chains, as well as the dependence of local dielectric permittivity on the polymer volume fraction Φ. The main focus is on the spinodal instability of polyelectrolyte solutions towards microscopic phase separation. It has been shown that increasing the binding energy of ions decreases the classical microphase separation region (possible at low polymer concentrations) due to the effective neutralization of the chains. A qualitatively new type of microphase separation is found in the presence of a dielectric mismatch between polymer and solvent. This new branch of microphase separation is realized at high polymer concentrations where ion association processes are the most pronounced. Typical microstructures are shown to have a period of a few nanometers like in ionomers. The driving force for the microphase formation of a new type is more favourable ion association in polymer-rich domains where ionomer-type behavior takes place. Effective attraction due to ion association promotes microscopic as well as macroscopic phase separation, even under good solvent conditions for uncharged monomer units of polymer chains. Polyelectrolyte-type behavior at low Φ and ionomer-type behavior at high Φ result in the presence of two critical points on the phase diagrams of polyelectrolyte solutions as well as two separate regions of possible microscopic structuring. Our predictions on the new type of microphase separation are supported by experimental data on polymer solutions, membranes and gels.

show abstract

Section: Introductionsupporting

confidence: 66%

Two regions of microphase separation in ion-containing polymer solutions

Rumyantsev

Kramarenko

2017

Soft Matter

View full text Add to dashboard Cite

show abstract

“…If there are no free counterions in PE gel, e.g., dense ionomer state is realized, gel conductivity is lower by far than that of a swollen gel . Similar conductivity drop at switching between PE and ionomer regimes was also observed for the case of PE solutions. − Thus, if there are free counterions within the polymer system, PEs resembles metals, while in the absence of free charge carriers their electrical properties are alike with the ones of dielectrics. Analogy between PEs and metals/dielectrics occurs to be very wide and expands over the conductivity problem being useful for analysis of PEs conformational behavior as well (see Supporting Information).…”

Section: Resultsmentioning

confidence: 70%

Polyelectrolyte Gel Swelling and Conductivity vs Counterion Type, Cross-Linking Density, and Solvent Polarity

et al. 2016

View full text Add to dashboard Cite

A joint theoretical and experimental study is devoted to the swelling and electrical conductivity of highly charged polyelectrolyte (PE) gels in media of different polarity. Deprotected poly(tert-butyl carbamate l-alanine) gels provided with fluorine, bromine, chlorine, sulfate, and trifluoroacetic counteranions demonstrated different conductivity in aqueous medium as well as solvent uptake in water/methanol mixtures. Counterion specificity in PE gel properties was theoretically explained in the framework of the model which treats ion association within the network as a two-stage process. Manning-type condensation, being the first condensation stage not affected by counterion type, provides understanding of a gel maximal swelling at intermediate degrees of gel ionization f and a slight gel contraction at f tending to unity, which were earlier observed in experimental investigations. The second ion association stage is an ion pairing influenced by the kind of counterion. Since a considerable fraction of ions form pairs even in a swollen hydrogel, its properties are largely influenced by counterion type. Conductivity of the gel was calculated theoretically owing to the known fraction of free and condensed counterions. Developed theory containing no adjusting parameters allows for the first time to reach semiquantitative matching of experimental results on highly charged gel swelling and conductivity.

show abstract

“…Similar behavior was recently observed by us at the titration of linear PAA with tetramethylammonium hydroxide in methanol solutions. 31,32 In this case, the specific viscosity first increases, then drops and finally recovers its maximum value with increasing degree of ionization. The initial drop of viscosity is accompanied by the decrease of the specific conductivity indicating the binding of some counterions with the formation of ion pairs.…”

Section: Resultsmentioning

confidence: 90%

“…The initial drop of viscosity is accompanied by the decrease of the specific conductivity indicating the binding of some counterions with the formation of ion pairs. 31,32 Simultaneously, the 1 H NMR shows the disappearance of the signals assigned to the protons of macromolecular chains, 31 which is due to the collapse of macromolecules resulting in the hindering of their internal motion. The latter leads to a drastic decrease of the spin−spin relaxation times of polymer protons, as a result, their signals widen to infinity and are not observed in the spectrum.…”

Section: Resultsmentioning

confidence: 98%

“…Simultaneously, the specific conductivity increases indicating the dissociation of ion pairs with the release of counterions. 31,32 Therefore, for counterions of intermediate size the transition from polyelectrolyte to ionomer regime is followed by a reentrant transition from ionomer to polyelectrolyte regime, when the degree of ionization increases. In the present study such double transition is first observed in polymer gels.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

New Type of Swelling Behavior upon Gel Ionization: Theory vs Experiment

et al. 2013

View full text Add to dashboard Cite

We report a combined experimental and theoretical study on the swelling behavior of polyelectrolyte gels with various types of counterions. Experimental research was focused on poly(methacrylic acid) and poly(acrylic acid) gels in methanol neutralized with different bases providing sodium, cesium, tetramethyl-, tetraethyl- or tetrabutylammonium counterions. The novelty of the theoretical treatment is that the counterion size is explicitly taken into account as well as the dependence of the ion association constant on the volume fraction of polymer within the gel. We demonstrate that, depending on the counterion size, three different regimes of the gel behavior are realized. In case of bulky tetrabutylammonium counterions the gel swells upon ionization. For small counterions (Na+, Cs+) the gel swelling at low ionization degrees is succeeded by its collapse. New type of behavior was observed and theoretically described for the gels with counterions of intermediate sizes (tetramethyl- and tetraethylammonium). In this case, the gel ionization causes first swelling, then collapse and finally reswelling of the gel. This distinction in gel behavior with counterions of different types is explained by decreasing tendency for ion pair and multiplet formation with growing counterion dimensions. Our finding of the counterion-controlled collapse/decollapse transition is significant for fundamental understanding of the role of ion association processes in polyelectrolyte gel behavior as well as for design of sensors and environmentally responsive containers for controlled delivery applications.

show abstract

Dual polyelectrolyte-ionomer behavior of poly(acrylic acid) in methanol: 2. Salt solutions

Cited by 5 publications

References 11 publications

Two regions of microphase separation in ion-containing polymer solutions

Two regions of microphase separation in ion-containing polymer solutions

Polyelectrolyte Gel Swelling and Conductivity vs Counterion Type, Cross-Linking Density, and Solvent Polarity

New Type of Swelling Behavior upon Gel Ionization: Theory vs Experiment

Contact Info

Product

Resources

About