Electric Charging in Nonpolar Liquids Because of Nonionizable Surfactants

Guo, Qiong; Singh, Virendra; Behrens, Sven H.

doi:10.1021/la903182e

Cited by 93 publications

(177 citation statements)

References 28 publications

(43 reference statements)

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“…The surfactants OLOA 11K (r ≈ 5.5 nm 11,25,26 ) and Span 80 (r ≈ 4 nm 26 ) are non-ionic while Solsperse 13940 (r ≈ 8 nm 26 ) is an ionic surfactant. The second category includes surfactant systems such as ionic sodium dioctylsulfosuccinate or Aerosol OT (AOT) (r ≈ 1.6 nm 2,3,26 ) and non-ionic sorbitan trioleate or Span 85 (r ≈ 3 nm 26,27 ), in which the generation rate of CIMs is much higher than their transportation rate to the opposite polarity electrode on application of an electric field. Therefore, in these surfactant systems, the concentration of CIMs in the bulk always remains approximately equal to the equilibrium concentration 24,26 .…”

Section: Introductionmentioning

confidence: 99%

Space charge limited release of charged inverse micelles in non-polar liquids

Prasad

Strubbe

Beunis

et al. 2016

Phys. Chem. Chem. Phys.

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Charged inverse micelles (CIMs) generated during a continuous polarizing voltage between electrodes in the model system of polyisobutylene succinimide in dodecane do not populate a diffuse double layer like CIMs present in equilibrium (regular CIMs), but instead end up in interface layers. When the applied voltage is reversed abruptly after a continuous polarizing voltage step, two peaks are observed in the transient current. The first peak is due to the release of regular CIMs from the diffuse double layers formed during the polarizing voltage step, which is understood on the basis of the Poisson-Nernst-Planck equations. The second peak is due to the release of a small fraction of generated negative CIMs from the interface layer. A model based on space charge limited release of the generated negative CIMs from the interface layer is presented and the results of the model are compared with several types of measurements. For the situation in which the bulk is deprived of regular CIMs and neutral inverse micelles, the results of the model are in agreement with the experimental results.However, for the situation in which regular CIMs and neutral inverse micelles are present, the 2 model shows discrepancies with the experiment for high voltages and high charge contents.These discrepancies are attributed to electrohydrodynamic flow caused by local variations in the electric field at the vicinity of the electrodes, which occur during the reversal voltage.Also the long term decrease of the amount of released generated CIMs is studied and it is found that the presence of regular CIMs and neutral inverse micelles speeds up the decrease.This study provides a deeper insight in the electrodynamics of CIMs and is relevant for various applications in non-polar liquids.

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Section: Introductionmentioning

confidence: 99%

Space charge limited release of charged inverse micelles in non-polar liquids

Prasad

Strubbe

Beunis

et al. 2016

Phys. Chem. Chem. Phys.

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“…11−13,27,28 A small fraction (10 −5 aerosol OT 11,13 and 0.1 polyisobutylene succinimide 24,29 (PIBS)) of the inverse micelles is charged as a result of a disproportionation/ comproportionation mechanism, 11,12,14,15,24,28 in which two uncharged inverse micelles exchange a charge and become a positively and a negatively charged inverse micelle and vice versa. Charged inverse micelles (CIMs) play an important role in charging and charge stabilization in nonpolar media.…”

Section: ■ Introductionmentioning

confidence: 99%

Different Types of Charged-Inverse Micelles in Nonpolar Media

et al. 2016

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Over the last few years, the electrodynamics of charged inverse micelles (CIMs) in nonpolar liquids and the generation mechanism and properties of newly generated CIMs have been studied extensively for the model system of polyisobutylene succinimide in dodecane. However, the newly generated CIMs, which accumulate at the electrodes when a continuous voltage is applied, behave differently compared to the regular CIMs present in equilibrium in the absence of a field. In this work, we use transient current measurements to investigate the behavior of the newly generated CIMs when the field is reduced to zero or reversed. We demonstrate that the newly generated CIMs do not participate in the diffuse double layer near the electrode formed by the regular CIMs but form an interface layer at the electrode surface. A fraction of the newly generated negative CIMs can be released from this interface layer when the field there becomes zero. The findings of this study provide a better understanding of fundamental processes in nonpolar liquids and are relevant for applications such as electronic ink displays and liquid toner printing. 23−26 have been used to study the mechanism of surfactant-mediated charging and charge stabilization in nonpolar media. From these studies, it has been concluded that charges in nonpolar surfactant systems exist in the form of inverse micelles that are formed above a certain surfactant concentration known as the critical micelle concentration. ■ INTRODUCTION11−13,27,28 A small fraction (10 −5 aerosol OT 11,13 and 0.1 polyisobutylene succinimide 24,29 (PIBS)) of the inverse micelles is charged as a result of a disproportionation/ comproportionation mechanism, 11,12,14,15,24,28 in which two uncharged inverse micelles exchange a charge and become a positively and a negatively charged inverse micelle and vice versa. Charged inverse micelles (CIMs) play an important role in charging and charge stabilization in nonpolar media. 11−15,30−32 Electrophoretic displays are based on the displacement of charged pigment particles between two electrodes in response to an applied voltage. 5,7,25 In these systems, surfactant is often added to charge and stabilize the pigment particles. 16,33,34 However, only a small fraction of surfactant molecules is adsorbed at the particle surfaces and other interfaces. Because of the presence of free CIMs, the nonpolar medium becomes more conductive, affecting the electric field and the switching characteristics of charged pigment particles. 21 Controlling the trajectory of particles in conductive media is challenging because of electrohydrodynamic flow, 7,29 which causes particle clustering 7 and pattern formation 35−37 at the electrodes, resulting in image degradation, increased power consumption, and reduced lifetimes of electrophoretic devices. 7 Many effects of charged inverse micelles can be studied without the presence of colloidal particles. 29,33,38 The electrical behavior of these nonpolar systems with surfactant is governed by the drift, diffusion, an...

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“…However, it was found that irrespective of the source of impurities, the conductivity is solely governed by the concentration of the non-ionic emulsifier [20]. The free ions can be carried by a single emulsifier molecule below the CMC (dissociation model) or accommodated inside inverse micelles above the CMC (fluctuation model) [17,18].…”

Section: Introductionmentioning

confidence: 99%

“…The free ions can be carried by a single emulsifier molecule below the CMC (dissociation model) or accommodated inside inverse micelles above the CMC (fluctuation model) [17,18]. For the fluctuation model, it is hypothesized that after collision of two neutral micelles, intermediate aggregates form which can split into two charged micelles through exchange of ions [20]. Applying the law of mass action for equilibrium in dissociation model, a square root relationship is obtained between the conductivity and emulsifier concentration σ∝ ffiffiffi ffi C p À Á while for the fluctuation model, a linear relationship (σ∝C) results.…”

Section: Introductionmentioning

confidence: 99%

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Characterizing colloidal behavior of non-ionic emulsifiers in non-polar solvents using electrical impedance spectroscopy

et al. 2014

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Colloidal behavior of a widely used non-ionic emulsifier, sorbitan monooleate (Span80), was investigated in non-polar solvents (cyclohexane and xylene) using electrical impedance spectroscopy (EIS). The electrical characteristics of the colloidal mixtures were measured with frequency scans ranging from 1 Hz to 200 kHz. The conductances at low frequencies were found to increase with an increase in Span80 concentration. The source of conductivity for non-polar solvents using non-ionic emulsifiers is usually attributed to ionic impurities either in the Span80 or in the non-polar solvents. The measured electrical characteristics for pure Span80 and pure non-polar solvents revealed that the source of ionic conduction is impurities in Span80. It was confirmed that the ionic impurities in the non-polar solvents are in form of aggregate of ions, ion-pairs, and triple ions which is unaffected with the emulsifier concentration. Analyses using equivalent electrical circuits confirmed that the critical MaxwellWagner frequency is 0.6-1.8 Hz for the mixtures. The conductance-concentration profiles for the mixtures at 1 Hz showed transitions from a square root to a linear concentration dependence at the CMC. This indicated that the dissociation model holds below the CMC, while the fluctuation model applies above the CMC. The conductance profiles enabled estimates of the relative hydrophilic core radius and the fraction of charged micelles in both non-polar solvents.

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Electric Charging in Nonpolar Liquids Because of Nonionizable Surfactants

Cited by 93 publications

References 28 publications

Space charge limited release of charged inverse micelles in non-polar liquids

Space charge limited release of charged inverse micelles in non-polar liquids

Different Types of Charged-Inverse Micelles in Nonpolar Media

Characterizing colloidal behavior of non-ionic emulsifiers in non-polar solvents using electrical impedance spectroscopy

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