Effect of planar extension on the structure and mechanical properties of polystyrene–poly(ethylene- co -butylene)–polystyrene triblock copolymers

Daniel, Christophe; Hamley, Ian W.; Mortensen, K.

doi:10.1016/s0032-3861(00)00308-6

Cited by 50 publications

(49 citation statements)

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“…At this high deformation, the macromolecular response of the copolymer dominates, causing integrated motion of PS blocks towards a parallel alignment. [11][12][13][14] However, as suggested by Daniel et al [21] and Pakula et al, [23] necking and rupture of domain structures takes place at very high elongational flows. Hence, with a combination of all these effects, we obtained very small and broken PS/PI domains, with some evidence of parallel alignment in as-spun coaxial fibers.…”

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confidence: 92%

“…In this effort to obtain novel morphologies in confined yet continuous and long nanostructures, we recently reported the structure development in polystyrene-block-polyisoprene (PS-b-PI) nanofibers [20] formed via electrospinning. However, the microdomains in as-spun fibers are largely disordered because of the strong elongational deformation [21][22][23] and rapid solvent evaporation [24] during electrospinning. Fong and Reneker [25] produced nanofibers from a styrene-butadiene-styrene triblock-copolymer solution by electrospinning.…”

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confidence: 99%

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Confined Assembly in Coaxially Electrospun Block Copolymer Fibers

et al. 2006

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Electrospinning has received a lot of attention in recent years as a simple process to produce sub-micrometer-scale fibers. The process involves continuous stretching of polymer solution or melt in the presence of a strong electric field, which forms ultrathin fibers. A large amount of research is being carried out to achieve control of the diameter, morphology, and spatial alignment of electrospun nanofibers. [1,2] Unlike other 1D nanostructures, such as nanowires and nanotubes, nanofibers exhibit a wide range of unique properties, making them far more attractive for many applications, such as filtration, catalysis, sensing, protective clothing, and tissueengineering scaffolds.[3] Being a continuous process, electrospinning can produce extremely long fibers comparable to those formed via conventional mechanical drawing and spinning techniques. Nanofiber mats exhibit extremely high surface-to-mass ratios, greatly improving their efficiency for catalysis and filtration. [2] Another fascinating feature of this process is that it can be applied to a wide variety of nanostructured materials. Bognitzki et al. [4] fabricated sub-micrometerscale fibers by electrospinning ternary solutions of polylactide and poly(vinylpyrrolidone). They found that the fibers displayed an internal phase morphology, and, by selectively removing one phase, they obtained highly porous fibers. However, these morphologies were largely controlled by rapid phase separation and rapid solidification of the polymer jet, and no method for controlling these morphologies was demonstrated. In the present study, we utilize this simple process to fabricate block copolymer (BCP) nanofibers. BCP solutions and melts are known to self-assemble into a variety of nanoscale morphologies including spheres, rods, micelles, lamellae, vesicles, tubules, and cylinders, [5,6] depending on the volume fraction and interaction parameter between different blocks. We have been able to produce macroscale-length fibers with diameters of a few hundred nanometers that exhibit internal structures of only tens of nanometers in size. Such materials, we believe, can combine the unique properties of continuous nanofibers and BCP self-assembly for use in a variety of applications of nanostructured materials. BCP self-assembly has attracted increasing interest in recent years for applications in nanotechnology.[7] Precise control over the size, shape, and periodicity of these nanoscale microdomains is the key factor needed to realize nanoscale systems. Various methods, including shear and elongational deformation, compressional deformation, electric fields, and temperature gradients, have been utilized to induce orientation of the microdomains. To our knowledge, shear flow has been most extensively studied as a simple means to induce phase transitions and orient self-assembled structures in block copolymers. [8,9] The phenomenon of flow-induced alignment of lamellar BCPs is very well studied in bulk systems. [10][11][12] Three different orientations of lamellar morphology, namely, p...

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Confined Assembly in Coaxially Electrospun Block Copolymer Fibers

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“…The shape memory property of thermopolastic dielectric elastomer results from physical cross-linking, which totally differs from that of conventional homopolymer dielectric elastomer that stems from chemical cross-linking as shown in Figure 2 ( Daniel et al, 2000;Drobny, 2007;Hamley, 2003;Koo, et al, 2006). The thermoplastic dielectric elastomers form microphase-separated agglomerates in a regular fashion.…”

Section: Fig 5 Cyclic Load-unload Compression Test Of a Sebs Thermomentioning

confidence: 99%

Electroactive Thermoplastic Dielectric Elastomers as a New Generation Polymer Actuators

Koo¹

2012

Thermoplastic Elastomers

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“…The modulus can be modeled by a rule-ofmixtures approach [30], such that in the composition range commonly observed in thermoplastic elastomers the modulus is profoundly influenced by the polystyrene content [31]. It must also be noted that the mechanical properties of these materials are known to be anisotropic [32][33][34]. The melt processing of block copolymers is known to orient the cylinders in the plane of melt flow [31,32] and it is anticipated that the cylinders in these block copolymer samples are aligned in the plane of the tensile elongation, but no attempt was made to interrogate the level of orientation.…”

Section: The Influence Of Pche Contentmentioning

confidence: 99%

“…It must also be noted that the mechanical properties of these materials are known to be anisotropic [32][33][34]. The melt processing of block copolymers is known to orient the cylinders in the plane of melt flow [31,32] and it is anticipated that the cylinders in these block copolymer samples are aligned in the plane of the tensile elongation, but no attempt was made to interrogate the level of orientation. These materials exhibited high ultimate tensile strength and high elongation at break.…”

Section: The Influence Of Pche Contentmentioning

confidence: 99%