Phase Separation in Ternary Polymer Solutions Induced by Solvent Loss

Hopkinson, Ian; Myatt, Matthew

doi:10.1021/ma012244p

Cited by 50 publications

(36 citation statements)

References 30 publications

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“…At this stage, it is not clear whether CMC and alginate chains remain intimately mixed (as in the wet state) or whether phase segregation occurs upon drying. Phase segregation upon drying has been reported previously for polymer mixtures 21 and is a topic of current investigation in our laboratory.…”

Section: Discussionsupporting

confidence: 58%

Drying and Rehydration of Calcium Alginate Gels

Vreeker

Fang

et al. 2008

Food Biophysics

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In this paper, we study the rehydration properties of air-dried calcium alginate gel beads. Rehydration is shown to depend on alginate source (i.e. mannuronic to guluronic acid ratio) and the salt concentration in the rehydration medium. Rehydration curves are described adequately by the empirical Weibull equation. Wide-angle X-ray diffraction measurements are performed to obtain information on the microstructure of dried alginate gels. The X-ray diffraction patterns provide evidence for formation of ordered domains in which alginate polymers are laterally associated. Formation of ordered structures during drying is found to have a large impact on rehydration properties. Lateral association of alginate chains is reduced (and rehydration improved) by removing excess calcium ions from the gel beads in a washing step prior to air drying. In addition, rehydration properties of mixed alginate-carboxymethyl cellulose (CMC) gel beads are investigated. The presence of CMC in the gel matrix is found to reduce lateral association of alginate chains during drying and to improve rehydration properties.

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Section: Discussionsupporting

confidence: 58%

Drying and Rehydration of Calcium Alginate Gels

Vreeker

Fang

et al. 2008

Food Biophysics

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“…A couple of different types of 3D microscopes have been developed. 15 They are laser scanning confocal microscopy (LSCM), [16][17][18][19][20][21][22][23][24][25][26][27] X-ray tomography, [28][29][30] and transmission electron microtomography (TEMT). 15, The spatial resolution of LSCM and X-ray tomography is on the order of a micrometer, while that of TEMT approaches 1 nm or less.…”

mentioning

confidence: 99%

Three-Dimensional Imaging in Polymer Science: Its Application to Block Copolymer Morphologies and Rubber Composites

Dohi¹,

Kimura²,

Kotani³

et al. 2007

Polym J

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ABSTRACT:New methods to visualize polymer morphologies in three-dimension (3D) in polymer science are reviewed. Here we concentrate on one of such 3D imaging technique, transmission electron microtomography (TEMT), and introduce some experimental studies using this novel technique. They are block copolymer morphologies during order-order transition between the two different morphologies and block copolymer thin film morphology also during morphological change due to confinement. Direct visualization of 3D structure of silica particle/rubber composite and related morphological analyses are shown. Subsequently, as a very hot topic of the 3D imaging, we show for the first time to characterize the morphological change in a silica particle/rubber composite upon stretching. It was found that the aggregates of silica particles were broken down upon stretching and many voids were generated near and between the silica particles. Local stress upon stretching inside the composite was inferred from the image intensity of the 3D reconstructed image. The local stress was found not only near the silica particles but also near the top of the voids. The observations indicated that the local stress increases the modulus, causing voids to form along the stretching direction. The thickness of the specimen after the stretching was also estimated from the 3D volume data, which turned out to be non-uniform and thinner than what is expected from the affine deformation. These experimental findings indicate that the rubber composite does not obey the assumption of the affine deformation at the nano-scale. Polymer materials are ubiquitous in our daily life. Such materials often consist of more than one species of polymers and thus become multi-component systems, such as in polymer blends, 1,2 block copolymers, 3 and fillers/polymer composites. 4 The multi-component systems often show phase-separated structures due to immiscibility of constituents. Studies to characterize such morphologies inside the materials have been growing intensively over the past few decades. Academic interest in complex fluids (to which polymeric systems belong) as well as the ceaseless industrial need for developing new materials motivates such studies.In academia, pattern formation and self-assembling processes of multi-component polymer systems are one of the most fascinating research themes in nonlinear, non-equilibrium phenomena.1 Likewise, nanometer-scale periodic structures formed in block copolymers in their equilibrium state are interesting because their self-assembly is driven by the subtle balance between the entropic block chain conformation and enthalpic interaction between the constituents. 3In industry, phase-separated polymer systems provide an important route to achieve superior physical properties. Hence, the structure-property relationship in multi-component polymeric materials is of significant importance, basic studies on which eventually render new designs of polymer materials satisfying the diverse requirements of industry.Filler/polymer comp...

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“…Optimization of the film preparation parameters results in a microphase structure that closely follows the patterns on the gold surface. This technology, initially developed using systems based on organic solvents is now being extended to aqueous systems using water-soluble polymers such as polyvinyl alcohol, polyethylene glycol, and dextran [3]. The elimination of organic solvents allows more environmentally friendly production methods as well as opening new possibilities for applications in fields such as biology: here, structured surfaces of water-soluble polymers are expected to have interesting cell-adhesion properties.…”

Section: Polymer Demixingmentioning

confidence: 99%

Nano-Structuring by Molecular Self-Assembly

Minelli¹,

Blondiaux²,

Losson³

et al. 2003

Chimia

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the new physical, chemical, or biological properties of surfaces structured using these methods. There is a special emphasis on structuring mechanisms relying on selfassembly, self-organization, and non-equilibrium processes, i.e. parallel approaches to the fabrication of large-area structures with high short-range order and some long-range order. In addition to this purely bottom-up approach based on self-organization of molecules, we also combine these selforganization methods with top-down, soft lithography techniques such as microfluidics for larger scale patterning of surfaces.Here we describe some different approaches to structuring surfaces. The first approach uses the ability of a spin-coated solution of two different homopolymers to demix and form micro-to nano-structured thin films with different morphologies. A very similar approach, used to create even smaller structures, with a higher degree of order is based on the phase separation of block-copolymers. This method gives chemically distinct domains with sizes ranging from 10 nm to 100 nm. Combining homopolymer and copolymer phase separation even allows the creation of polymeric films with structures on two length scales. The final example described here demonstrates the self-assembly and complexation properties of dendrimers, highly branched monodisperse macromolecules with welldefined structure, geometry, and monodispersity.Abstract: In contrast to conventional lithography techniques which will soon hit their limits in terms of feature size and fabrication cost, recent years have seen considerable progress in the development of selfassembling nano-structured surfaces. In the work reported here, surface structures on the submicron scale have been created from polymer, copolymer, nanoparticle, and dendrimer building blocks by employing phenomena such as self-assembly, self-organization and non-equilibrium processes. This low-cost approach is expected to result in a new generation of surfaces with novel physical and chemical properties.

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Phase Separation in Ternary Polymer Solutions Induced by Solvent Loss

Cited by 50 publications

References 30 publications

Drying and Rehydration of Calcium Alginate Gels

Drying and Rehydration of Calcium Alginate Gels

Three-Dimensional Imaging in Polymer Science: Its Application to Block Copolymer Morphologies and Rubber Composites

Nano-Structuring by Molecular Self-Assembly

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