Solvent‐solubility‐parameter‐dependent homogeneity and sol–gel transitions of concentrated polyacrylonitrile solutions

Li, Weijie; Hao, Jian; Zhou, Pengpeng; Liu, Yaodong; Lü, Chunxiang; Zhang, Zhengfang

doi:10.1002/app.45405

Cited by 23 publications

(15 citation statements)

References 31 publications

(36 reference statements)

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“…These solvents differ in affinity to PAN. It changes in accordance with the following rank: DMSO > DMF > DMAc~NMP [74]. All solvents were produced by Ecos-1 Co. (Russia) and were used as supplied.…”

Section: Methodsmentioning

confidence: 99%

A Novel Technique for Fiber Formation: Mechanotropic Spinning—Principle and Realization

et al. 2018

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We present basic experimental data and the theoretical background of a novel technique for fiber spinning from polymer solutions. The principal feature of the advanced process is realization of phase separation with detachment of a solvent, accompanied by the orientation of macromolecules, under the action of high extension rates. This is similar in some respects to dry spinning, though the driving force is not diffusion with subsequent evaporation of a solvent but redistribution of polymer-solvent interactions in favor of polymer-polymer and solvent-solvent ones governed by mechanical stresses. A promise of this approach has been demonstrated by experiments performed with polyacrylonitrile solutions in different solvents and solutions of the rigid-chain aromatic polyamide. We examined mechanotropic fiber spinning in model experiments with stretching jets from a drop of polymer solution in different conditions, and then demonstrated the possibility of realizing this process in the stable long-term continuous mode. During extension, phase separation happens throughout the whole section of a jet, as was confirmed by visual observation. Then a solvent diffuses on a jet surface, forming a liquid shell on the oriented fiber. Instability of this cover due to surface tension leads either to formation of separate solvent drops “seating” on the fiber or to the flow of a solvent down to the Taylor cone. The separate liquid droplets can be easily taken off a fiber. The physics underlying this process is related to the analysis of the influence of macromolecule coil-to-stretched chain transition on the intermolecular interaction.

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Section: Methodsmentioning

confidence: 99%

A Novel Technique for Fiber Formation: Mechanotropic Spinning—Principle and Realization

et al. 2018

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“…PAN/DMSO solution with a weight fraction of 20% was prepared according to a reported dissolution procedure . The PAN solution (dope temperature 50~60 °C) was spun using a stainless steel syringe equipped a 1.27 cm long blunt tip (hole diameter 510 μm) and self‐made high pressure injection pump, which was the same spinning equipment in our previous studies .…”

Section: Methodsmentioning

confidence: 99%

A comparison of coagulation and gelation on the structures and stabilization behaviors of polyacrylonitrile fibers

Wei

Suo

Lü

et al. 2019

J of Applied Polymer Sci

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The fiber spinning methods determine the formation of the physical structures of polyacrylonitrile (PAN) fibers which further affect stabilization reactions and the mechanical performances of the resultant carbon fibers. In this study, PAN fibers were prepared by both dry-jet gel spinning (g-PAN) and dry-jet wet spinning (w-PAN), and their stabilization behaviors were compared. While the stabilized w-PAN fibers show sheath-core structures, the stabilized g-PAN fibers exhibit relatively uniform stabilized structures along the radial direction. Additionally, the stabilization reactions of g-PAN fibers occur faster than that of w-PAN fibers, and the cyclization, oxidation, and crosslinking reaction activation energies of g-PAN fibers are lower than that of w-PAN fibers, respectively. Moreover, the carbon yield of g-PAN is higher than that of w-PAN fibers. We believe that above changes are possibly ascribed to the formation of different PAN sheath structures and oriented chain structures during dry-jet wet spinning and dry-jet gel spinning. It is concluded that gel spinning could significantly reduce the sheath-core difference of PAN fibers and the stabilized fibers as compared with wet spinning, which leads to a faster stabilization and more uniform stabilized structures.

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“…In common polar aprotic solvents such as N , N ‐DMF, N , N ‐DMAc, and DMSO, PAN produces optically transparent solutions but exhibits different solubility and rheological heterogeneity depending on the chemical affinity with the solvent molecules . Hence, the choice of a solvent system in processing PAN solutions for fiber or film preparation is crucial to obtain desired properties of final products, because the polymer solubility in a given solvent significantly affects the phase characteristics and resulting processibility of the solutions.…”

Section: Introductionmentioning

confidence: 99%

“…INTRODUCTION In common polar aprotic solvents such as N, N-DMF, N, N-DMAc, and DMSO, PAN produces optically transparent solutions but exhibits different solubility and rheological heterogeneity depending on the chemical affinity with the solvent molecules. 1,2 Hence, the choice of a solvent system in processing PAN solutions for fiber or film preparation is crucial to obtain desired properties of final products, because the polymer solubility in a given solvent significantly affects the phase characteristics and resulting processibility of the solutions. The dipole-dipole interaction between nitrile groups of PAN results in the intermolecular interactions of polymer molecules even in the solution state, which causes abnormal phase behaviors with respect to environmental and processing conditions such as the temperature and the concentration.…”

mentioning

confidence: 99%

Enthalpic effect of polyacrylonitrile on the concentrated solutions in dimethyl sulfoxide: Strong thixotropic behavior and formation of bound solvents

Eom

Kim

et al. 2019

J Polym Sci B Polym Phys

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The effect of dipole-dipole interaction by nitrile groups of PAN on the bound state of solvent molecules and the concentrated solution properties in DMSO was investigated. Variation of a solution viscosity exhibited three overlap concentrations, C1*, C2*, and C3*, at 2.7, 8.6, and 16.3 wt%, respectively, representing the transition of concentration regions in the order of dilute, unentangled-semi dilute, entangled-semi dilute, and concentrated regions. The two-dimensional mapping of FT-IR analysis and dielectric measurement confirmed that the intermolecular interaction of PAN was suddenly enhanced at the C*s, inducing polarization to DMSO. In the ice-melting process of PAN solutions, two different melting peaks (T m 2 and T m 3) of DMSO newly appeared at each C2* and C3*, suggesting the different types of bound solvents. In the concentrated solutions, the saturated dielectric constant and the strongly delayed evaporation of the solvent even at the boiling point of DMSO along with strong thixotropic behavior were indicative of the stronger confinement state of bound DMSO than in the semidilute solutions.

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Solvent‐solubility‐parameter‐dependent homogeneity and sol–gel transitions of concentrated polyacrylonitrile solutions

Cited by 23 publications

References 31 publications

A Novel Technique for Fiber Formation: Mechanotropic Spinning—Principle and Realization

A Novel Technique for Fiber Formation: Mechanotropic Spinning—Principle and Realization

A comparison of coagulation and gelation on the structures and stabilization behaviors of polyacrylonitrile fibers

Enthalpic effect of polyacrylonitrile on the concentrated solutions in dimethyl sulfoxide: Strong thixotropic behavior and formation of bound solvents

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