Microphase structure of block ionomers. 3. A SAXS study of the effects of architecture and chemical structure

Gouin, Jean Pierre; Bosse, F.; Nguyen, Diep; Williams, C. E.; Eisenberg, Adi

doi:10.1021/ma00078a021

Macromolecules

1993

DOI: 10.1021/ma00078a021

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Microphase structure of block ionomers. 3. A SAXS study of the effects of architecture and chemical structure

Jean Pierre Gouin¹,

F. Bosse²,

Diep Nguyen³

et al.

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Cited by 20 publications

(21 citation statements)

References 17 publications

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“…[4] However, only reverse spherical micelles have been reported for this block ionomer family in toluene. [5] Combination of S n -b-V m with oppositely charged block ionomers leads to formation of asymmetric vesicles. [6] Here we report the preparation of POM/block copolymer composites and their self-assembly into micelles and vesicles in organic solvents.…”

mentioning

confidence: 99%

“…Block ionomers with long hydrophobic blocks and short hydrophilic blocks form spherical micelles in hydrophobic organic solvents. [5,10] In contrast, incorporation of large amounts of POMs into S n -b- Unperturbed end-to-end distance of the S block. R 0 = 0.456 n 0.595 .…”

mentioning

confidence: 99%

“…[7] The SSS regime can be reached if 1) the interfacial tension between insoluble blocks and solvents/soluble blocks is rather high, 2) attraction between insoluble blocks is very strong, and 3) the length of insoluble blocks is relatively small. [5,7,13] The SAXS studies by Eisenberg et al showed that the ionic core radii of reverse micelles of S n -b-V m with long V blocks (m ! 30) are shorter than the contour lengths of the V blocks, because the entropy is decreased by stretching the long V blocks.…”

mentioning

confidence: 99%

“…Therefore, packing parameters such as the interfacial area per chain (A c ), chain stretching degree (S c ) for V blocks, and aggregation number (N agg ) were calculated to characterize the micellar and vesicular structures quantitatively (Table 1). [3][4][5] The N agg values of the SVP composites were much larger than those of the parent S n -b-V m , and this suggests that the interfacial tensions are high. The S c values of the vesicles (0.18-0.42) were smaller than those of the micelles (1.12), while the A c values of the vesicles (3.9-8.4 nm 2 ) were larger than those of the micelles (3.1-3.9 nm 2 ).…”

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Micelles and Vesicles Formed by Polyoxometalate–Block Copolymer Composites

Uchida

Mizuno

2009

Angewandte Chemie

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Polyoxometalates (POMs) are anionic metal oxide clusters with several to a few tens of negative charges, and their structural and electronic versatility has resulted in various applications in the fields of catalysis, biomedicine, and materials science. [1] However, these hydrophilic clusters are basically incompatible with hydrophobic organic materials and have high lattice energies associated with crystallization. Therefore, further fabrication of POM-based materials and devices requires manipulating the clusters on the nanoscale through solution-based self-assembly.The surface properties of POMs can be modified by replacement of the countercations with cationic surfactants to form surfactant-encapsulated clusters (SECs). [2] The resultant SECs are soluble in organic media and facilitate fabrication of POM-based thin films such as Langmuir monolayers, Langmuir-Blodgett films, and solvent-cast films. On the other hand, ionic block copolymers are macromolecular analogues of conventional ionic surfactants. They can self-assemble into regular and reverse micellelike nanosized aggregates in aqueous media and nonpolar organic solvents, respectively. [3] The morphologies of the aggregates primarily depend on the incompatibility between blocks, block compositions, and solvents.Poly(styrene-b-4-vinyl-N-methylpyridinium iodide), S n -b-V m , with long S and short V blocks can form multiple morphologies of aggregates (i.e., sphere, cylinder, and bilayer) on dispersion in water. [4] However, only reverse spherical micelles have been reported for this block ionomer family in toluene. [5] Combination of S n -b-V m with oppositely charged block ionomers leads to formation of asymmetric vesicles. [6] Here we report the preparation of POM/block copolymer composites and their self-assembly into micelles and vesicles in organic solvents. The micelles reach the superstrong segregation (SSS) regime, where the ionic core radii correspond to the length of fully stretched V blocks, the interface is totally occupied by S/V junction points, and no more space is available to incorporate chains. [7] The POM/S n -b-V m (SVP) composites ( Figure 1) were prepared by electrostatic incorporation of POMs into solid S n -b-V m matrices as follows: Na 3 [a-PW 12 O 40 ] was dissolved in water and the pH value modified to 0.7-0.8 with aqueous HNO 3 . [8] This solution was added to a suspension of S n -b-V m powder (n = 240, m = 65; n = 480, m = 57; and n = 1171, m = 206) in water. The resultant mixture was vigorously stirred for 3 d and the solid product collected (SVP-1 to SVP-7). The IR spectra of the composites showed the characteristic bands of both [a-PW 12 O 40 ] 3À and block ionomers. [9] The compositions of SVP-1-SVP-7 and parameters such as the weight fractions of POM (W POM ) and hydrophilic volumes (V h ) are listed in Table 1.Since the S blocks are soluble in toluene and the V blocks in combination with POM are insoluble in toluene, the selfassembled morphologies of these composites in toluene were studied with transmission electron m...

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mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Micelles and Vesicles Formed by Polyoxometalate–Block Copolymer Composites

Uchida

Mizuno

2009

Angewandte Chemie

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mentioning

confidence: 99%

Micelles and Vesicles Formed by Polyoxometalate–Block Copolymer Composites

2009

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Polyoxometalates (POMs) are anionic metal oxide clusters with several to a few tens of negative charges, and their structural and electronic versatility has resulted in various applications in the fields of catalysis, biomedicine, and materials science.[1] However, these hydrophilic clusters are basically incompatible with hydrophobic organic materials and have high lattice energies associated with crystallization. Therefore, further fabrication of POM-based materials and devices requires manipulating the clusters on the nanoscale through solution-based self-assembly.The surface properties of POMs can be modified by replacement of the countercations with cationic surfactants to form surfactant-encapsulated clusters (SECs).[2] The resultant SECs are soluble in organic media and facilitate fabrication of POM-based thin films such as Langmuir monolayers, Langmuir-Blodgett films, and solvent-cast films. On the other hand, ionic block copolymers are macromolecular analogues of conventional ionic surfactants. They can self-assemble into regular and reverse micellelike nanosized aggregates in aqueous media and nonpolar organic solvents, respectively.[3]The morphologies of the aggregates primarily depend on the incompatibility between blocks, block compositions, and solvents.Poly(styrene-b-4-vinyl-N-methylpyridinium iodide), S n -b-V m , with long S and short V blocks can form multiple morphologies of aggregates (i.e., sphere, cylinder, and bilayer) on dispersion in water.[4] However, only reverse spherical micelles have been reported for this block ionomer family in toluene.[5] Combination of S n -b-V m with oppositely charged block ionomers leads to formation of asymmetric vesicles.[6] Here we report the preparation of POM/block copolymer composites and their self-assembly into micelles and vesicles in organic solvents. The micelles reach the superstrong segregation (SSS) regime, where the ionic core radii correspond to the length of fully stretched V blocks, the interface is totally occupied by S/V junction points, and no more space is available to incorporate chains. [7] The POM/S n -b-V m (SVP) composites (Figure 1) were prepared by electrostatic incorporation of POMs into solid S n -b-V m matrices as follows: Na 3 [a-PW 12 O 40 ] was dissolved in water and the pH value modified to 0.7-0.8 with aqueous HNO 3 .[8] This solution was added to a suspension of S n -b-V m powder (n = 240, m = 65; n = 480, m = 57; and n = 1171, m = 206) in water. The resultant mixture was vigorously stirred for 3 d and the solid product collected (SVP-1 to SVP-7). The IR spectra of the composites showed the characteristic bands of both 3À and block ionomers.[9] The compositions of SVP-1-SVP-7 and parameters such as the weight fractions of POM (W POM ) and hydrophilic volumes (V h ) are listed in Table 1.Since the S blocks are soluble in toluene and the V blocks in combination with POM are insoluble in toluene, the selfassembled morphologies of these composites in toluene were studied with transmission electron microscopy (TEM). A typical ...

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Controlled Hydrophobic Functionalization of Natural Fibers through Self‐Assembly of Amphiphilic Diblock Copolymer Micelles

et al. 2013

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The functionalization of natural fibers is an important task that has recently received considerable attention. We investigated the formation of a hydrophobic layer from amphiphilic diblock copolymer micelles [polystyrene-block-poly(N-methyl-4-vinyl pyridinium iodide)] on natural fibers and on a model surface (mica). A series of micelles were prepared. The micelles were characterized by using cryoscopic TEM and light scattering, and their hydrophobization capability was studied through contact angle measurements, water adsorption, and Raman imaging. Mild heat treatment (130 °C) was used to increase the hydrophobization capability of the micelles. The results showed that the micelles could not hydrophobize a model surface, but could render the natural fibers water repellent both with and without heat treatment. This effect was systematically studied by varying the composition of the constituent blocks. The results showed that the micelle size (and the molecular weight of the constituent diblock copolymers) was the most important parameter, whereas the cationic (hydrophilic) part played only a minor role. We hypothesized that the hydrophobization effect could be attributed to a combination of the micelle size and the shrinkage of the natural fibers upon drying. The shrinking caused the roughness to increase on the fiber surface, which resulted in a rearrangement of the self- assembled layer in the wet state. Consequently, the fibers became hydrophobic through the roughness effects at multiple length scales. Mild heat treatment melted the micelle core and decreased the minimum size necessary for hydrophobization.

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Microphase structure of block ionomers. 3. A SAXS study of the effects of architecture and chemical structure

Cited by 20 publications

References 17 publications

Micelles and Vesicles Formed by Polyoxometalate–Block Copolymer Composites

Micelles and Vesicles Formed by Polyoxometalate–Block Copolymer Composites

Micelles and Vesicles Formed by Polyoxometalate–Block Copolymer Composites

Controlled Hydrophobic Functionalization of Natural Fibers through Self‐Assembly of Amphiphilic Diblock Copolymer Micelles

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