Amphiphilic copolymers and their applications

Alexandridis, Paschalis

doi:10.1016/s1359-0294(96)80118-x

Cited by 331 publications

(242 citation statements)

References 65 publications

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“…In the second place, block copolymers provide a steric stabilization to emulsions, since they adsorb in the water-oil interface and create a barrier for droplet coalescence. 26 These two phenomena resulted in the proved highstability of the gel emulsions formed up to 70 wt%. For highly-concentrated emulsions, as the liquid crystal fraction was less, the two stabilizing effects diminished.…”

Section: Formation and Stability Of W/i 2 And W/h 2 Gel Emulsionsmentioning

confidence: 98%

Phase Behavior and Rheological Analysis of Reverse Liquid Crystals and W/I₂ and W/H₂ Gel Emulsions Using an Amphiphilic Block Copolymer

2011

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This article reports the phase behavior determination of a system forming reverse liquid crystals, and the formation of novel disperse systems in the two-phase region. The studied system is formed by water, cyclohexane, and Pluronic L-121, an amphiphilic block copolymer considered of special interest due to its aggregation and structural properties. This system forms reverse cubic (I 2 ) and reverse hexagonal (H 2 ) phases at high polymer concentrations. These reverse phases are of particular interest, since in the two-phase region, stable high internal phase reverse emulsions can be formed. The characterization of Published in: Langmuir, February 2, 2011, Volume 27, Number 6, Pages 2286-2298 the I 2 and H 2 phases and of the derived gel emulsions was performed with small-angle X-ray scattering (SAXS) and rheometry, and the influence of temperature and water content was studied. The H 2 phase experimented a thermal transition to an I 2 phase when temperature was increased, which presented an Fd3m structure. All samples showed a strong shear thinning behavior from low shear rates. The elastic modulus (G') in the I 2 phase was around one order of magnitude higher than in the H 2 phase. G' was predominantly higher than the viscous modulus (G''). In the gel emulsions, G' was nearly frequencyindependent, indicating their gel type nature. Contrarily to water-in-oil (W/O) normal emulsions, in W/I 2 and W/H 2 gel emulsions, G', the complex viscosity (|*|) and the yield stress ( 0 ) decreased with increasing water content, since the highly viscous microstructure of the continuous phase was responsible for the high viscosity and elastic behavior of the emulsions, instead of the volume fraction of dispersed phase and droplet size. A rheological analysis, in which the cooperative flow theory, the soft glass rheology model and the slip plane model were analyzed and compared, was performed to obtain one single model that could describe the non-Maxwellian behavior of both reverse phases and highly-concentrated emulsions and to characterize their microstructure with the rheological properties.

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Section: Formation and Stability Of W/i 2 And W/h 2 Gel Emulsionsmentioning

confidence: 98%

Phase Behavior and Rheological Analysis of Reverse Liquid Crystals and W/I₂ and W/H₂ Gel Emulsions Using an Amphiphilic Block Copolymer

2011

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“…1,2 It is now well established that these block copolymers can phase separate into a variety of organized structures (lamellae, cylinder, double gyroid, spherical etc.) in the solid state, 3 and form a variety of micellar aggregates (spherical and cylindrical micelles, vesicles etc.)…”

Section: Introductionmentioning

confidence: 99%

Self-assembly of liquid crystal block copolymer PEG-b-smectic polymer in pure state and in dilute aqueous solution

Piñol

Nono-Djamen

et al. 2009

Faraday Discuss.

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2 SummaryA series of amphiphilic LC block copolymers, in which the hydrophobic block is a smectic polymer poly(4-methoxyphenyl 4-(6-acryloyloxyhexyloxy)-benzoate) (PA6ester1) and the hydrophilic block is polyethyleneglycol (PEG), were synthesized and characterized. The selfassembly of one of them in both the pure state and the dilute aqueous solution was investigated in detail. Nano-structures in the pure state were studied by SAXS and WAXS on samples aligned by a magnetic field. A hexagonal cylindrical micro-segregation phase was observed with a lattice distance of 11.2 nm. The PEG blocks are in the cylinder, while the smectic polymer blocks form a matrix with layer spacing 2.4 nm and layer normal parallel to the long axis of the cylinders. Faceted unilamellar polymer vesicles, polymersomes, were formed in water, as revealed by cryo-TEM. In the lyotropic bilayer membrane of these polymersomes, the thermotropic smectic order in the hydrophobic block is clearly visible with layer normal parallel to the membrane surface.3

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“…B lock copolymers in solutions or melts are known to self-assemble into mesophases with one-, two-, or threedimensional periodic order with typical repeating distances in the 10Ϫ200 nm range. 1,2 In solutions, the self-assembly of the different phases can be controlled by tuning external conditions such as pH or temperature. The wide availability and relatively inexpensive synthesis of block copolymers as well as the ability to exquisitely control so many diverse phases with periodic order make them compelling candidates for the building blocks of novel materials.…”

Section: Introductionmentioning

confidence: 99%

Nanoparticle Ordering via Functionalized Block Copolymers in Solution

Sknepnek¹,

Anderson²,

Lamm

et al. 2008

ACS Nano

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We consider nanoparticles and functionalized copolymers, block copolymers with attached end groups possessing a specific affinity for nanoparticles, in solution. Using molecular dynamics, we show that nanoparticles are able to direct the self-assembly of the polymer/ nanoparticle composite. We perform a detailed study for a wide range of nanoparticle sizes and concentrations. We show that the nanoparticles order in a number of distinct phases: simple cubic, layered hexagonal, hexagonal columnar, gyroid, and a novel square columnar. Our results show that nanoparticles ordered with functionalized block copolymers can provide a simple and efficient tool for assembling novel materials with nanometer scale resolution. B lock copolymers in solutions or melts are known to self-assemble into mesophases with one-, two-, or threedimensional periodic order with typical repeating distances in the 10Ϫ200 nm range. 1,2 In solutions, the self-assembly of the different phases can be controlled by tuning external conditions such as pH or temperature. The wide availability and relatively inexpensive synthesis of block copolymers as well as the ability to exquisitely control so many diverse phases with periodic order make them compelling candidates for the building blocks of novel materials. Thin films of block copolymers can provide "bottom-up" templates for fabrication of devices on sub-30-nm length scales that are inaccessible to standard lithography techniques, opening the door for molecular size electronic components and ultrahigh density magnetic storage media. Applications include growth of nanowires 3,4 and nanocrystals used in devices such as flash memory, 5 metal-oxidesemiconductor capacitors, 6,7 arrays of quantum dots, 8,9 and photonic crystals. 10 For most applications, the proposed fabrication process consists of forming a thin copolymer film on a substrate, which is then chemically treated to remove one of the copolymer components. The remaining component is used as a mask for growing the active component. It would be even more desirable to include the active component (e.g., metallic or silica nanoparticles) from the outset and form the desired structure in a single pass. Direct application of this method is limited mainly due to nanoparticle aggregation and incompatibility of nanoparticle surface and ionic solutions with the polymers. 11 These problems can be circumvented by the use of self-assembling functionalized block copolymers, that is, polymers with covalently attached end groups that show specific affinity for nanoparticles, as agents for assembling ordered nanoparticle structures. 12,13 The theoretical understanding of the factors that lead to a successful self-assembly of nanocomposites is relatively limited. Recent studies include investigations of the influence of nanoparticles on the selfassembly and nanostructure formation of diblock copolymer melts based on solving cell dynamical system equations, 14 Monte Carlo simulations, 15 and self-consistent mean field/density functional theory. 16,17 ...

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Amphiphilic copolymers and their applications

Cited by 331 publications

References 65 publications

Phase Behavior and Rheological Analysis of Reverse Liquid Crystals and W/I₂ and W/H₂ Gel Emulsions Using an Amphiphilic Block Copolymer

Phase Behavior and Rheological Analysis of Reverse Liquid Crystals and W/I₂ and W/H₂ Gel Emulsions Using an Amphiphilic Block Copolymer

Self-assembly of liquid crystal block copolymer PEG-b-smectic polymer in pure state and in dilute aqueous solution

Nanoparticle Ordering via Functionalized Block Copolymers in Solution

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Amphiphilic copolymers and their applications

Cited by 331 publications

References 65 publications

Phase Behavior and Rheological Analysis of Reverse Liquid Crystals and W/I2 and W/H2 Gel Emulsions Using an Amphiphilic Block Copolymer

Phase Behavior and Rheological Analysis of Reverse Liquid Crystals and W/I2 and W/H2 Gel Emulsions Using an Amphiphilic Block Copolymer

Self-assembly of liquid crystal block copolymer PEG-b-smectic polymer in pure state and in dilute aqueous solution

Nanoparticle Ordering via Functionalized Block Copolymers in Solution

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Product

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Phase Behavior and Rheological Analysis of Reverse Liquid Crystals and W/I₂ and W/H₂ Gel Emulsions Using an Amphiphilic Block Copolymer

Phase Behavior and Rheological Analysis of Reverse Liquid Crystals and W/I₂ and W/H₂ Gel Emulsions Using an Amphiphilic Block Copolymer