Shear-induced nematic phase in entangled rod-like PEEK melts

Parisi, Daniele; Seo, Jiho; Schaake, Richard P.; Rhoades, Alicyn M.; Colby, Ralph H.

doi:10.1016/j.progpolymsci.2020.101323

Cited by 11 publications

(14 citation statements)

References 108 publications

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“…DPD simulations demonstrate that Zn−polymer coordination induces multichain clustering by cross-linking the chains, and the XG solutions above a certain polymer concentration undergo a sol−gel transition. Such transition is welldocumented in metal-complexed polymer solutions; 73 it was observed in our previous DPD simulations of the complexation effects in concentrated polymer solutions. 8 DPD simulations demonstrate that the XG chains undergo an orientational transition in shear flows with sufficiently large shear rates.…”

Section: Dpd Modeling Of Morphological Transitionssupporting

confidence: 71%

“…With no Zn added, the chains undergo an orientational transition (OT) from randomly oriented conformations at zero shear to conformations that are aligned along the direction of flow as the shear rate increases from 0 to 0.05 τ –1 . OT happens at a sufficiently high shear rate, as this transition is not observed at a low shear rate of γ s = 0.0005 τ –1 and is the shear-induced isotropic-to-nematic transition observed in rod-like polymers that is responsible for the shear thinning effect. OT tends to hinder the overlap between the chains and reduces viscosity.…”

Section: Results and Discussionmentioning

confidence: 93%

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Modeling of the Effects of Metal Complexation on the Morphology and Rheology of Xanthan Gum Polysaccharide Solutions

et al. 2021

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Polysaccharide solutions commonly contain metal ions, which form cross-linking complexes with polymer ligands and significantly affect the polymer morphology and solution rheology. Here, we study by multiscale computational modeling complemented with atomic force microscopy (AFM) measurements the molecular mechanisms of metal complexation with examples of xanthan gum (XG) solutions containing ZnCl2. We develop original atomistic molecular dynamics (MD) and coarse-grained dissipative particle dynamics (DPD) models for XG chains of different compositions and Zn complexation. MD simulations reveal that Zn dramatically affects conformations of individual XG chains, causing a reduction in the radius of gyration by the formation of various types of intrachain cross-linking that are enhanced by the increased pyruvate content in the chains. DPD simulations at the static conditions and under the shear flow show that salt addition leads to gelation in XG systems via a sol–gel transition due to enhanced interchain cross-linking. Two morphological transitions occur in the shear flow: an orientational transition to a nematic phase with XG chains aligned in the direction of flow and a bundling transition accompanied by a reverse gel–sol transition at high Zn concentrations. The presence of the increased pyruvate content in the chains leads to stronger aggregation and stiffer aggregates, in qualitative agreement with AFM results. The proposed computational methodology of modeling the effects of metal complexation and chain composition on morphological and rheological properties may be extended and applied to various polysaccharide systems.

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Section: Dpd Modeling Of Morphological Transitionssupporting

confidence: 71%

Section: Results and Discussionmentioning

confidence: 93%

Modeling of the Effects of Metal Complexation on the Morphology and Rheology of Xanthan Gum Polysaccharide Solutions

et al. 2021

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“…The planar Grandjean texture of the N* mesophase is obtained similar to the planar texture in ordinary nematic, that is, by imposing boundary conditions such that the molecules in contact with the bonding surfaces are aligned parallel to these surfaces. The resulting texture is durable and can last for a long time, many months, or even years. − …”

Section: Resultsmentioning

confidence: 99%

Poly(l-Lactide) Liquid Crystals with Tailor-Made Properties Toward a Specific Nematic Mesophase Texture

Janeczek

Duale

Sikorska

et al. 2022

ACS Sustainable Chem. Eng.

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This paper presents the liquid crystal (LC) properties of poly( l -lactide) (PLLA). Mesophase behavior is investigated using polarized optical microscopy, X-ray diffraction, and differential scanning calorimetry. The performed analyses confirm that pressed PLLA films exhibit the unique capability of self-assembling into a nematic mesophase under the influence of mechanical pressure, temperature, and time. It was originally demonstrated that the chiral nematic mesophase can be obtained by introducing fine powders into the polymer. Based on the research conducted, it was proved that the pressed PLLA films have a chiral nematic mesophase with a nematic-to-isotropic phase transition and a large mesophase stability range overlapping the temperature of the human body, which can persist for years at ambient temperature. The obtained films show tailor-made properties toward a nematic mesophase with a specific texture, including colored planar texture of the chiral nematic mesophase and blue-phase (BP) LC texture. The BP, described for the first time in plain PLLA, occurred over a wider than usual temperature range of stability between isotropic and chiral nematic thermotropic phases (Δ T ≈ 9 °C), which is an advantage of the obtained polymer material, in addition to ease of preparation. This opens up new prospects for advanced photonic green applications.

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“…Recently, the crystallization behavior of highperformance thermoplastics under flow has attracted great attention. Here we taking poly(3-hexylthiophene)/ toluene (P3HT), [199][200][201] an organic optoelectronic material, and polyether ether ketone (PEEK), 101,102,[202][203][204] a hightemperature resistant and tough material, as examples. Sun et al 199 used in situ SR-SAXS/WAXS, DSC, ultraviolet-visible absorption spectroscopy and polarized optical microscopy to study the ordered-disordered transition of P3HT solutions under cooling and heating processes.…”

Section: Fic Of Developed Materialsmentioning

confidence: 99%

Recent progress in flow‐induced polymer crystallization

Nie

Fan

Cao

et al. 2022

Journal of Polymer Science

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During industrial processing, such as film blowing and injection molding, semicrystalline polymers have to be subjected to external flow. Flow changes the nucleation rate, crystal morphology and polymorphism of polymers. As flow can be tunable, polymeric products with different macroscopic performance and versatile applications can be obtained. Understanding polymer crystallization with the presence of flow, or namely flow-induced crystallization (FIC), is crucial to optimize polymer processing parameters and to understand phase transition under far-from equilibrium conditions, as FIC is essentially a typical nonequilibrium process. Current review aims to summarizes recent achievements of FIC during last five years from three aspects: theory, experiment and simulation. First, we present the FIC model and theory, including the classical conformational entropy reduction model, the newly developed POLYdisperse STRain Accelerated Nucleation Dynamics (PolySTRAND) Model and uFIC Model. Then we discuss the FIC experiments under both well-controlled flow and complex processing conditions. Finally, we show the recent advance of FIC in computer simulation. With the fast development in modeling efficiency, more detailed nucleation and structure transition processes during FIC can be obtained, which promote the study of molecular mechanisms of FIC.

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Shear-induced nematic phase in entangled rod-like PEEK melts

Cited by 11 publications

References 108 publications

Modeling of the Effects of Metal Complexation on the Morphology and Rheology of Xanthan Gum Polysaccharide Solutions

Modeling of the Effects of Metal Complexation on the Morphology and Rheology of Xanthan Gum Polysaccharide Solutions

Poly(l-Lactide) Liquid Crystals with Tailor-Made Properties Toward a Specific Nematic Mesophase Texture

Recent progress in flow‐induced polymer crystallization

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