Adsorption Studies of Diblock Copolymers at the Cyclohexane/Carbon Black Interface

Shar, JA; Cosgrove, Terence; Obey, Timothy M.; Warne, M. R.; Wedlock, D.J.

doi:10.1021/la990050l

Cited by 12 publications

(21 citation statements)

References 21 publications

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“…60 In the context of the present work, when the star copolymer is added to carbon black particles in n-alkanes, it is assumed that the polystyrene blocks act as "stickers" that aid copolymer adsorption onto the carbon black (see Figure 1), which is known to be a useful mimic for diesel engine soot. 35,66−69 A representative transmission electron micrograph of the commercial carbon black (Regal 250 R) employed in this study confirms its characteristic fractal morphology (see Figure S4). According to our earlier study, 70 BET surface area analysis (N 2 adsorbate at 77 K) indicated a specific surface area of 43 m g −1 for this material.…”

Section: ■ Results and Discussionsupporting

confidence: 66%

Star Diblock Copolymer Concentration Dictates the Degree of Dispersion of Carbon Black Particles in Nonpolar Media: Bridging Flocculation versus Steric Stabilization

et al. 2015

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The solution behavior of a polystyrene− hydrogenated polyisoprene star diblock copolymer (M n ∼ 384 K; 6 mol % polystyrene) is examined in nonpolar media. Variable temperature 1 H NMR studies using deuterated ndodecane confirm that the outer polystyrene blocks are only partially solvated in n-dodecane at 25°C: the apparent polystyrene content of 3.2 ± 0.2 mol % remains essentially constant on heating up to 100°C. Physical adsorption of this star diblock copolymer onto carbon black particles is examined, with particular attention being paid to the effect of copolymer concentration on colloidal stability. An isotherm is constructed for copolymer adsorption onto carbon black from n-dodecane at 20°C using a supernatant depletion assay based on UV spectroscopy analysis of the aromatic chromophore in the polystyrene block. Langmuir-type adsorption is observed with a maximum adsorbed amount, Γ, of ∼2.2 ± 0.1 mg m −2 . In addition, thermogravimetric analysis is used to directly determine the amount of adsorbed copolymer on the carbon black particles, which are essentially incombustible under an inert atmosphere. Analytical centrifugation, optical microscopy, and transmission electron microscopy studies indicate that the star diblock copolymer acts as an effective flocculant at low concentration, with steric stabilization only being observed above a certain critical copolymer concentration (∼5.5% w/w based on carbon black). This is attributed to the spatial location of the polystyrene block and the star copolymer architecture, which enables copolymer adsorption onto multiple carbon black particles at low coverage, leading to bridging flocculation. Above 5.5% w/w copolymer, the surface coverage is sufficiently high that all of the polystyrene "stickers" adsorb onto single carbon black particles, resulting in colloidally stable, sterically stabilized carbon black dispersions. Small-angle Xray scattering (SAXS) is also used to characterize the copolymer-coated carbon black particles: this technique provides useful complementary insights regarding the rather subtle changes in the fractal morphology that occur with increasing copolymer concentration. Moreover, SAXS also provides direct evidence for the presence of the copolymer chains at the particle surface.

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Section: ■ Results and Discussionsupporting

confidence: 66%

Star Diblock Copolymer Concentration Dictates the Degree of Dispersion of Carbon Black Particles in Nonpolar Media: Bridging Flocculation versus Steric Stabilization

et al. 2015

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“…In this scheme, the adsorption is assumed to be a Langmuir type, which is widely used in adsorption models for proteins, [39][40][41] inorganic nanoparticles 42,43 and polymers. 44,45 Therefore, the relationship between the concentration of the PNDDS in the solution (m s ) and the concentration of the PNDDS on the root surface (C) is as follows:…”

Section: Kinetics Of Pndds Uptakementioning

confidence: 99%

Uptake and translocation of polymeric nanoparticulate drug delivery systems into ryegrass

et al. 2012

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“…38 In both cases, carbon black was selected as a colloidal substrate for such studies because this material has been shown to be a convenient mimic for diesel soot particles. 36,39 The latter are formed during incomplete fuel combustion in diesel engines and are known to lead to longterm engine wear and reduced fuel economy. 40−42 Thus, suitable oil-soluble block copolymers that can minimize diesel soot formation and/or aid its dispersion on the nanometer scale are routinely added to engine oil formulations to address this problem and hence improve performance.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Such diblock copolymers can be prepared by living anionic polymerization of styrene with either butadiene or isoprene followed by catalytic hydrogenation using nickel-based catalysts. 36 This usually ensures well-defined diblock copolymers with minimal homopolymer contamination and relatively narrow molecular weight distributions. 25 Chloroform and n-dodecane solvents were obtained from Fisher Scientific UK Ltd. and were used as received.…”

Section: ■ Introductionmentioning

confidence: 99%

Determination of Effective Particle Density for Sterically Stabilized Carbon Black Particles: Effect of Diblock Copolymer Stabilizer Composition

et al. 2015

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Two poly(styrene-b-hydrogenated isoprene) (PS-PEP) copolymers and a poly(styrene-b-hydrogenated butadiene) (PS-PB) diblock copolymer of differing polystyrene content (20, 28 or 35 mol %) and molecular weight (117-183 kg mol(-1)) are examined. These copolymers form star-like micelles in n-dodecane, as judged by TEM, DLS, and SAXS studies. At ambient temperature, such micelles are known to adsorb intact onto a model colloidal substrate such as carbon black, conferring a high degree of dispersion (Growney, D. J.; Mykhaylyk, O. O.; Armes, S. P. Langmuir 2014, 30, 6047). Isotherms for micellar adsorption on carbon black at 20 °C are constructed using a supernatant depletion assay based on UV spectroscopy by utilizing the aromatic chromophore in the polystyrene block. Perhaps surprisingly, the diblock copolymer with the lowest polystyrene content has the strongest affinity for the carbon black particles. Assuming that the star-like diblock copolymer micelles adsorb onto carbon black to form hemi-micelles with a stabilizer layer thickness equal to the mean micelle radius, the effective particle density of the resulting sterically stabilized carbon black particles in n-dodecane can be estimated from the SAXS micelle dimensions based on geometric considerations. As an approximation, a spherical core-shell morphology was assumed, and the primary grain size of the carbon black particles was determined to be 74 nm diameter as judged by BET surface area analysis. Using this approach, effective particle densities of 0.90, 0.91, and 0.92 g cm(-3) were calculated for sterically stabilized carbon black particles prepared using the PS-PB20, PS-PEP28, and PS-PEP35 diblock copolymers, respectively. These densities are significantly lower than that of carbon black (1.89 g cm(-3)), which indicates that the sterically stabilized carbon black particles are substantially solvated. Since the rate of sedimentation of the sterically stabilized carbon black particles depends on the density difference between the effective particle density and that of n-dodecane (0.75 g cm(-3)), particle size analysis via analytical centrifugation incurs large sizing errors unless the above corrected effective particle densities are utilized. This is important because analytical centrifugation is a highly convenient technique for assessing the relative degree of dispersion of sterically stabilized carbon black particles, which are utilized to inkjet inks and coatings formulations.

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Adsorption Studies of Diblock Copolymers at the Cyclohexane/Carbon Black Interface

Cited by 12 publications

References 21 publications

Star Diblock Copolymer Concentration Dictates the Degree of Dispersion of Carbon Black Particles in Nonpolar Media: Bridging Flocculation versus Steric Stabilization

Star Diblock Copolymer Concentration Dictates the Degree of Dispersion of Carbon Black Particles in Nonpolar Media: Bridging Flocculation versus Steric Stabilization

Uptake and translocation of polymeric nanoparticulate drug delivery systems into ryegrass

Determination of Effective Particle Density for Sterically Stabilized Carbon Black Particles: Effect of Diblock Copolymer Stabilizer Composition

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