What conjugated polyelectrolytes tell us about aggregation in polyelectrolyte/surfactant systems

Burrows, Hugh D.; Valente, Artur J.M.; Costa, Telma; Stewart, Beverly; Tapia, María J.; Scherf, Ullrich

doi:10.1016/j.molliq.2015.04.012

Cited by 27 publications

(19 citation statements)

References 101 publications

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“…The variation in κ with the concentration of DeTAB shows an expected profile with two linear regions, at pre- and post-CMC regions, with an estimated CMC of 0.065 (± 0.005) mol L −1 , in agreement with the literature [ 53 , 54 ]. In the presence of 10 wt.% kraft lignin, the conductometric behavior of DeTAB changes significantly, and two remarks are worth noting: 1) the electrical conductivity is lower than in the absence of lignin, which may be related to an increase in the viscosity or due to the surfactant–polymer attractive interactions inducing some charge neutralization (this is consistent with the decrease in the slope of κ= f ([DeTAB]) [ 55 ], and 2) the dependence of κ with[DeTAB] shows three inflection points rationalized as follows. The first one, occurring at a DeTAB concentration around 0.015 mol L −1 , can be assigned to the CAC [ 56 ] relative to polymer-free micelle formation, which marks the onset of the association between the polymer and the surfactant; the second inflection point corresponds to the polymer saturation point (PSP), attributed to the surfactant concentration needed to saturate the polymer chains [ 34 , 57 , 58 , 59 ].…”

Section: Resultsmentioning

confidence: 85%

Enhancing Lignin Dissolution and Extraction: The Effect of Surfactants

et al. 2021

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The dissolution and extraction of lignin from biomass represents a great challenge due to the complex structure of this natural phenolic biopolymer. In this work, several surfactants (i.e., non-ionic, anionic, and cationic) were used as additives to enhance the dissolution efficiency of model lignin (kraft) and to boost lignin extraction from pine sawdust residues. To the best of our knowledge, cationic surfactants have never been systematically used for lignin dissolution. It was found that ca. 20 wt.% of kraft lignin is completely solubilized using 1 mol L−1 octyltrimethylammonium bromide aqueous solution. A remarkable dissolution efficiency was also obtained using 0.5 mol L−1 polysorbate 20. Furthermore, all surfactants used increased the lignin extraction with formic acid, even at low concentrations, such as 0.01 and 0.1 mol L−1. Higher concentrations of cationic surfactants improve the extraction yield but the purity of extracted lignin decreases.

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Section: Resultsmentioning

confidence: 85%

Enhancing Lignin Dissolution and Extraction: The Effect of Surfactants

et al. 2021

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“…Their aqueous solubility makes them valuable as sensors of biological or chemical systems [ 4 , 5 , 6 , 7 , 8 , 9 ], whilst their ionic character provides the potential for use in optoelectronics [ 10 ], as charge injection or transport layers [ 11 ], in light emitting devices [ 12 ], or as solar concentrators [ 13 ]. In addition, as polyelectrolytes, they can self-assemble with oppositely charged species, such as surfactants, to build up complex multilayer structures with various potential materials applications [ 14 , 15 ]. They can also bind oppositely charged electronic energy acceptors, such as [Ru(bpy) 3 ] 2+ , for artificial light harvesting [ 16 ].…”

Section: Introductionmentioning

confidence: 99%

Effects of Charge Density on Photophysics and Aggregation Behavior of Anionic Fluorene-Arylene Conjugated Polyelectrolytes

et al. 2018

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Three anionic fluorene-based alternating conjugated polyelectrolytes (CPEs) have been synthesized that have 9,9-bis(4-phenoxy-butylsulfonate) fluorene-2,7-diyl and 1,4-phenylene (PBS-PFP), 4,4′-biphenylene (PBS-PFP2), or 4,4″-p-terphenylene (PBS-PFP3) groups, and the effect of the length of the oligophenylene spacer on their aggregation and photophysics has been studied. All form metastable dispersions in water, but can be solubilized using methanol, acetonitrile, or dioxane as cosolvents. This leads to increases in their emission intensities and blue shifts in fluorescence maxima due to break-up of aggregates. In addition, the emission maximum shifts to the blue and the loss of vibronic structure are observed when the number of phenylene rings is increased. Debsity Functional Theory (DFT) calculations suggest that this is due to increasing conformational flexibility as the number of phenylene rings increases. This is supported by increasing amplitude in the fast component in the fluorescence decay. The nonionic surfactant n-dodecylpentaoxyethylene glycol ether (C12E5) also breaks up aggregates, as seen by changes in fluorescence intensity and maximum. However, the loss in vibrational structure is less pronounced in this case, possibly due to a more rigid environment in the mixed surfactant-CPE aggregates. Further information on the aggregates formed with C12E5 was obtained by electrical conductivity measurements, which showed an initial increase in specific conductivity upon addition of surfactants, while at higher surfactant/CPE molar ratios a plateau was observed. The specific conductance in the plateau region decreased in the order PBS-PFP3 < PBS-PFP2 < PBS-PFP, in agreement with the change in charge density on the CPE. The reverse process of aggregate formation has been studied by injecting small volumes of solutions of CPEs dissolved at the molecular level in a good solvent system (50% methanol-water) into the poor solvent, water. Aggregation was monitored by changes in both fluorescence and light scattering. The rate of aggregation increases with hydrophobicity and concentration of sodium chloride but is only weakly dependent on temperature.

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“…In order to avoid these problems, aqueous surfactants have been used to break CPE aggregates. − These systems have two interesting properties. First, surfactants can form a layer between CPEs and water, controlling polymer aggregation.…”

Section: Introductionmentioning

confidence: 99%

Incorporation of a Cationic Conjugated Polyelectrolyte CPE within an Aqueous Poly(vinyl alcohol) Sol

et al. 2016

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We report on a multiscale polymer-within-polymer structure of the cationic conjugated polyelectrolyte poly{[9,9-bis(6′-N,N,N-trimethylammonium)hexyl]fluorene−phenylene} (HTMA-PFP) in aqueous poly(vinyl alcohol) (PVA) sol. Molecular dynamics simulations and small-angle neutron scattering (SANS) data show that HTMA-PFP forms aggregates in water but becomes entangled by PVA (with a 1:1 molar ratio of HTMA-PFP to PVA) and eventually immersed in PVA clusters (with the ratio 1:4). This is attributed to the hydrophobic−hydrophilic balance. Contrast variation data with regular and deuterated PVA support a rigid body model, where HTMA-PFP is confined as locally isolated, but closely located, chains within PVA clusters, which alter correlation distances within the system. These results are supported by enhanced photoluminescence (PL) and ionic conductivity which, together with a red-shift in UV/vis absorption spectra, indicate the breakup of HTMA-PFP aggregates upon PVA addition.

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What conjugated polyelectrolytes tell us about aggregation in polyelectrolyte/surfactant systems

Cited by 27 publications

References 101 publications

Enhancing Lignin Dissolution and Extraction: The Effect of Surfactants

Enhancing Lignin Dissolution and Extraction: The Effect of Surfactants

Effects of Charge Density on Photophysics and Aggregation Behavior of Anionic Fluorene-Arylene Conjugated Polyelectrolytes

Incorporation of a Cationic Conjugated Polyelectrolyte CPE within an Aqueous Poly(vinyl alcohol) Sol

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