Unsteady-State Diffusion in Block Copolymers with Lamellar Domains

Faridi, Niloufar; Hadj-Romdhane, Ilyess

doi:10.1021/ie00037a045

Cited by 12 publications

(18 citation statements)

References 21 publications

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“…The partition coefficient ( K ) and diffusion coefficient ( D ) of toluene in PB and PS are K PB = 194, K PS = 183, D PB = 2.67 × 10 –6 cm 2 /s, and D PS = 7.37 × 10 –12 cm 2 /s. , Therefore, toluene molecules preferentially escape through PB domains rather than through PS domains. Furthermore, it was reported that solvent mobility is dependent on the tortuosity associated with the BCP morphology and orientation . For example, lamellae oriented parallel to the particle surface should impede toluene diffusion from the particle center to the surface, due to continuous PS layers parallel to the surface.…”

Section: Results and Discussionmentioning

confidence: 99%

“…The partition coefficient (K) and diffusion coefficient (D) of toluene in PB and PS are K PB = 194, K PS = 183, D PB = 2.67 × 10 −6 cm 2 / s, and D PS = 7.37 × 10 −12 cm 2 /s. 36,56 Therefore, toluene molecules preferentially escape through PB domains rather than through PS domains. Furthermore, it was reported that solvent mobility is dependent on the tortuosity associated with the BCP morphology and orientation.…”

Section: Resultsmentioning

confidence: 99%

“…Furthermore, it was reported that solvent mobility is dependent on the tortuosity associated with the BCP morphology and orientation. 56 For example, lamellae oriented parallel to the particle surface should impede toluene diffusion from the particle center to the surface, due to continuous PS layers parallel to the surface. On the other hand, lamellae oriented perpendicularly to the particle surface provide effective pathways for toluene to diffuse through the PB domains to the surface.…”

Section: Resultsmentioning

confidence: 99%

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Morphological Evolution of Block Copolymer Particles: Effect of Solvent Evaporation Rate on Particle Shape and Morphology

Shin¹,

Kim²,

Yun³

et al. 2017

ACS Nano

132

159

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Shape and morphology of polymeric particles are of great importance in controlling their optical properties or self-assembly into unusual superstructures. Confinement of block copolymers (BCPs) in evaporative emulsions affords particles with diverse structures, including prolate ellipsoids, onion-like spheres, oblate ellipsoids, and others. Herein, we report that the evaporation rate of solvent from emulsions encapsulating symmetric polystyrene-b-polybutadiene (PS-b-PB) determines the shape and internal nanostructure of micron-sized BCP particles. A distinct morphological transition from the ellipsoids with striped lamellae to the onion-like spheres was observed with decreasing evaporation rate. Experiments and dissipative particle dynamics (DPD) simulations showed that the evaporation rate affected the organization of BCPs at the particle surface, which determined the final shape and internal nanostructure of the particles. Differences in the solvent diffusion rates in PS and PB at rapid evaporation rates induced alignment of both domains perpendicular to the particle surface, resulting in ellipsoids with axial lamellar stripes. Slower evaporation rates provided sufficient time for BCP organization into onion-like structures with PB as the outermost layer, owing to the preferential interaction of PB with the surroundings. BCP molecular weight was found to influence the critical evaporation rate corresponding to the morphological transition from ellipsoid to onion-like particles, as well as the ellipsoid aspect ratio. DPD simulations produced morphologies similar to those obtained from experiments and thus elucidated the mechanism and driving forces responsible for the evaporation-induced assembly of BCPs into particles with well-defined shapes and morphologies.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Morphological Evolution of Block Copolymer Particles: Effect of Solvent Evaporation Rate on Particle Shape and Morphology

Shin¹,

Kim²,

Yun³

et al. 2017

ACS Nano

132

159

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“…The l p values in our system can be determined by estimating the coefficients in eq . First, the partition coefficient ( H ) of the poly(styrene- b -butadiene- b -styrene) (SBS) and toluene system at 30 °C was estimated to be 618 from the literature . The diffusivity of toluene ( D ) within the droplet was obtained from the equation − where D o is the solvent self-diffusivity, Φ p is the volume fraction of polymer and χ p ‑ s is the Flory–Huggins interaction parameter between the polymer components and the solvent.…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, we used the Fox equation for PS and toluene to find the Φ p of PS that yields a T g = 30 °C as where the T g , p of neat PS (373 K) and T g , s of toluene (137.5 K) were used to calculate the weight fraction of polymer ( w p ), which yielded the volume fraction Φ p of 0.842 . The D o of toluene at 30 °C was estimated to be 10 –8 cm 2 /s from the literature . Inserting all of these values into eq with χ PS ‑ tol = 0.34, we obtained D = 1.07 × 10 –10 cm 2 /s.…”

Section: Resultsmentioning

confidence: 99%

Aspect Ratio-Controlled Synthesis of Uniform Colloidal Block Copolymer Ellipsoids from Evaporative Emulsions

Shin

Kim

et al. 2018

Chem. Mater.

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Block copolymers (BCPs) confined in evaporative emulsions can assemble into ellipsoidal particles when solvent evaporation is faster than polymer diffusion within the droplet. Here, we report the synthesis of monodisperse, ellipsoidal polystyrene-block-1,4-polybutadiene (PS-b-PB) BCP particles with tunable aspect ratios (ARs) ranging from 1.0 to 2.2 and particle sizes ranging from 0.1 to 5 μm by membrane emulsification and subsequent solvent evaporation. The ratio of the propagation distance (l p) of ordered BCP domains perpendicular to the particle surface to the particle size (r BCP), or l p/r BCP, was found to be a critical parameter dictating the particle shape, where l p/r BCP > 1 yielded ellipsoids. We show that the AR of colloidal BCP ellipsoids can be precisely controlled by varying particle size (i.e., membrane pore size) and BCP molecular weight, as predicted by theoretical calculations of the free energy of particle elongation including three terms: (1) the interfacial energy between the two blocks of the BCP, (2) the entropic penalty associated with stretching of the BCP chains upon elongation of the particles, and (3) the surface energy between the BCP particles and the surrounding medium. Finally, using the resulting AR-controlled and highly monodisperse colloidal ellipsoids, we systematically investigated the effects of AR on the homogeneity of colloidal coatings obtained by drop-casting the ellipsoids into films.

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Block Copolymers, Transport Through

Zielinski

2001

Encyclopedia of Materials: Science and Technology

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Unsteady-State Diffusion in Block Copolymers with Lamellar Domains

Cited by 12 publications

References 21 publications

Morphological Evolution of Block Copolymer Particles: Effect of Solvent Evaporation Rate on Particle Shape and Morphology

Morphological Evolution of Block Copolymer Particles: Effect of Solvent Evaporation Rate on Particle Shape and Morphology

Aspect Ratio-Controlled Synthesis of Uniform Colloidal Block Copolymer Ellipsoids from Evaporative Emulsions

Block Copolymers, Transport Through

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