Extrusion of triblock and pentablock copolymers: Evolution of bulk and surface morphology

Phatak, Alhad; Macosko, Christopher W.; Bates, Frank S.; Hahn, Stephen F.

doi:10.1122/1.1822928

Cited by 14 publications

(10 citation statements)

References 37 publications

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“…However, isotropic samples of both polymers show nearly identical tensile properties and may be used interchangeably. Also worth mentioning is that macroscopically oriented samples obtained by extrusion of CEC-1 through a slit die 31 showed similar (as CEC-2) anisotropy in mechanical properties (brittle along the lamellae normal; ductile, parallel to the lamellar interface) but were too small to conduct a detailed study of the dependence of f on θ vx .…”

Section: Results and Analysismentioning

confidence: 99%

Toughness of Glassy−Semicrystalline Multiblock Copolymers

et al. 2006

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We report a study on the mechanical properties of lamellae-forming glassy−semicrystalline block copolymers composed of poly(cyclohexylethylene) (C) and polyethylene (E). Tensile properties of polydomain CEC, ECEC, CECEC, and ECECE block copolymers, and blends of these materials, reveal a critical dependence on the connectivity of the semicrystalline E blocks. A molecular parameter directly related to the fraction of bridging E blocks is identified, which captures the fracture behavior of C/E block copolymers over a range of chain architectures. Tensile testing and small-angle X-ray scattering (SAXS) experiments on aligned block copolymers reveal the role of bridging in the glassy C block and further elucidate the mechanisms that govern the deformation of microphase-separated lamellar domains and macroscopic fracture in glassy−semicrystalline block copolymers.

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Section: Results and Analysismentioning

confidence: 99%

Toughness of Glassy−Semicrystalline Multiblock Copolymers

et al. 2006

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“…Beyond their reversible character, TPEs (and more generally block copolymers) present the great asset to be highly sensitive to the processing methods, − i.e., tunable in terms of structure and properties, another important advantage with respect to their vulcanized counterparts. Among them, poly(ether–ester)s composed of poly(butylene terephthalate) (PBT) and polytetrahydrofuran (PTHF) units are synthesized industrially for more than 40 years because of their versatile mechanical behavior, chemical resistance, thermal stability, and rapid crystallization. − Nevertheless, in spite of an intense research activity aiming at understanding their structure–properties relationship, the impact of the processing conditions on the morphology of these semicrystalline copolymers still remains elusive, albeit highly relevant for the production at an industrial scale.…”

Section: Introductionmentioning

confidence: 99%

Process-Oriented Structure Tuning of PBT/PTHF Thermoplastic Elastomers

et al. 2018

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The multiscale structure of thermoplastic elastomers (TPEs) made of poly(butylene terephthalate)/ polytetrahydrofuran (PBT/PTHF) segmented block copolymers is investigated in a systematic way with the aim to characterize the impact of the processing route on it. By means of atomic force microscopy and small-angle scattering techniques, we first evidence the presence of thick (ca. 11 nm) and well-aligned ribbons in hot-pressed samples, whereas thinner and branched filaments (ca. 5 nm) are observed when solvent casting is used. Besides, differential scanning calorimetry suggests that all the so-formed structures can "remember" their initial state after being melted, a property that we assign to the persistent phase separation of the constituents in the viscoelastic liquid. At a smaller length scale, combining transmission and reflection wide-angle X-ray scattering experiments further reveals the influence of the processing method on the molecular order within the crystallites. In particular, it makes emerge the pronounced orthotropic character of the whole samples set, being to our knowledge totally ignored in the TPE's literature. In light of this extensive characterization, we end the article with a discussion on the relationship between the crystalline network's structure and the corresponding chains topology.

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“…The most comprehensive studies of flow alignment of multiblock copolymers have focused on ABA or ABC triblock and ABABA pentablock copolymer melts [73,[142][143][144][145][146]. Although triblock copolymers share common features with diblocks, they exhibit a greater sensitivity to experimental conditions, and several contradictory results have been reported [73,128,[142][143][144].…”

Section: Role Of Block Complexitymentioning

confidence: 99%

“…These phenomena are associated with peculiar variations of the viscosity with the shear rate. In pentablock copolymers [145,146], the only stable arrangement is the low-frequency perpendicular orientation. A transition to a disordered state occurs at high frequency.…”

Section: Role Of Block Complexitymentioning

confidence: 99%