Dissecting Dynamics Near the Glass Transition Using Polyelectrolyte Complexes

Schlenoff, Joseph B.; Akkaoui, Khalil

doi:10.1021/acs.macromol.1c00427

Cited by 14 publications

(12 citation statements)

References 58 publications

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“…This cooperativity is not reflected in the viscoelasticity until four charges are involved. In a recent mechanism for polymer/polymer coacervates, we concluded that the minimum cooperatively rearranging unit in PEC dynamics was an exchange of two Pol + Pol − pairs with a relaxation rate for PDADMA/PSS of about 10 4 s −1 ( 56 ). A ω b of about 10 5 s −1 in Fig.…”

Section: Resultsmentioning

confidence: 90%

Valence-induced jumps in coacervate properties

et al. 2022

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Spontaneous phase separation, or coacervation, of oppositely charged macromolecules is a powerful and ubiquitous mechanism for the assembly of natural and synthetic materials. Two critical triggering phenomena in coacervation science and technology are highlighted here. The first is the transition from one (mixed) to two (separated) phases of polyelectrolytes coacervated with small molecules upon the addition of one or two charges per molecule. The second is a large jump in coacervate modulus and viscosity mediated by the addition of just one additional charge to a three-charged system. This previously unknown viscoelastic transition is relevant to those aspects of disease states that are characterized by abnormal mechanical properties and irreversible assembly.

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Section: Resultsmentioning

confidence: 90%

Valence-induced jumps in coacervate properties

et al. 2022

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“…The highest frequency cross-over point is the inverse of the Pol + Pol – pairing lifetime τ min . It indicates the time it takes for a small number of Pol + Pol – pairs to cooperatively rearrange by place exchange. , In the present case, the number of cooperatively relaxing units, n , for 1/τ min = ω of 313 rad s –1 at 45 °C was estimated using data and equations from a recent publication . If T is much greater than T g , the polymer is in the Arrhenius regime for relaxation rate and n = 2 (two Pol + Pol – pairs in PECs) …”

Section: Resultsmentioning

confidence: 99%

“…59,60 In the present case, the number of cooperatively relaxing units, n, for 1/τ min = ω of 313 rad s −1 at 45 °C was estimated using data and equations from a recent publication. 61 If T is much greater than T g , the polymer is in the Arrhenius regime for relaxation rate and n = 2 (two Pol + Pol − pairs in PECs) 59…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Influence of Nonstoichiometry on the Viscoelastic Properties of a Polyelectrolyte Complex

et al. 2021

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Depending on conditions such as the mixing ratio, speed and order of addition, and ionic strength, when solutions of oppositely charged polyelectrolytes are mixed, the stoichiometry of the formed polyelectrolyte complexes (PECs) can vary. In fact, for most conditions, some degree of nonstoichiometry is inevitable because the ratios of positive and negative charges do not "lock" themselves to 1:1, as was believed in some early work. PEC morphologies and mechanical properties depend on the molar ratio between the polycation and polyanion. In this work, poly(diallyldimethylammonium) and poly(styrene sulfonate) were used to make PECs with varying stoichiometries. PECs that were overcompensated with one polyelectrolyte were shown to have lower glass transition temperatures and moduli due to the plasticizing effect caused by increased water content. In addition, time−temperature superposition revealed a correlation between segmental relaxation times and stoichiometry. Nonstoichiometric PECs were shown to have elevated fractional free volumes and decreased polymer volume fractions, which are responsible for changes in their mechanical properties.

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“…Poly(diallyldimethylammonium chloride) (molar mass, MM, 200 000–250 000 g mol –1 ) was from Sigma-Aldrich and fractionated as described previously to give M w = 70 000, PDADMAC . Two chain lengths of poly(styrene sulfonate) are denoted as “short chain” (S-PSS) and “long chain” (L-PSS).…”

Section: Methodsmentioning

confidence: 99%

“…Poly(diallyldimethylammonium chloride) (molar mass, MM, 200 000−250 000 g mol −1 ) was from Sigma-Aldrich and fractionated as described previously to give M w = 70 000, PDADMAC. 44 Two chain lengths of poly(styrene sulfonate) are denoted as "short chain" (S-PSS) and "long chain" (L-PSS). Deuterated poly(styrene sulfonate) with M w =104 000, L-dPSS, and M w 14 000, S-dPSS, were matched with protiated poly(styrene sulfonate) (M w 104 000, L-hPSS), made from polystyrene as described by Coughlin et al 45 The level of initial deuteration varied between samples because the polymers were sulfonated with either D 2 SO 4 or H 2 SO 4 .…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

Self-Exchange of Polyelectrolyte in Multilayers: Diffusion as a Function of Salt Concentration and Temperature

2021

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Polymer chain diffusion within a hydrated polyelectrolyte complex, PEC, has been measured using an ultrathin film format prepared by the layer-by-layer method. Isotopically labeled self-exchange of deuterated poly(styrene sulfonate), dPSS, with undeuterated PSS of the same narrow molecular weight distribution permitted reliable estimates of whole-molecule diffusion coefficients, D . N a r r o w m o l e c u l a r w e i g h t d i s t r i b u t i o n p o l y -(diallyldimethylammonium), PDADMA, was used as the polycation for the PEC. Extensive pretreatment of starting films was undertaken to remove residual stress, anisotropy, and layering. PSS/PDADMA "multilayers," PEMUs, thin enough to provide substantial exchange of polyelectrolyte, even with diffusion coefficients as low as 10 −16 cm 2 s −1 , as a function of salt concentration and temperature were measured for this PEC, which has a glass-transition temperature, T g , close to room temperature. Two molecular weights of dPSS, about 15 and 100 kDa, presumed to be below and above the entanglement molecular weight, respectively, both diffused faster at higher temperatures with respective activation energies, E a , of about 21 and 53 kJ mol −1 , the latter about the same as E a for the place exchange between two pairs of PSS:PDADMA. Studies of the linear viscoelastic response of macroscopic PECs showed a difference of about 8 °C in the T g of the two lengths of PSS complexed with the same PDADMA. Increasing concentrations of NaCl influenced D of 100 kDa PSS but not 15 kDa PSS at room temperature. D was faster in the region of the film near the solution interface, again attributed to a lower T g caused by greater water content at this interface.

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Dissecting Dynamics Near the Glass Transition Using Polyelectrolyte Complexes

Cited by 14 publications

References 58 publications

Valence-induced jumps in coacervate properties

Valence-induced jumps in coacervate properties

Influence of Nonstoichiometry on the Viscoelastic Properties of a Polyelectrolyte Complex

Self-Exchange of Polyelectrolyte in Multilayers: Diffusion as a Function of Salt Concentration and Temperature

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