Polymerization kinetics of rodlike molecules under quiescent conditions

Gupta, Jagriti; Agge, Ameya; Khakhar, D. V.

doi:10.1002/aic.690470117

Cited by 13 publications

(33 citation statements)

References 24 publications

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“…Figure 9 shows that there is a good match between the simulated data points and the fitted curve. k rel,0 can be estimated from the model proposed by Gupta et al, 6 and this in combination with the present model gives the estimate of k rel,Pe for a given Peclet number.…”

Section: B Variation Of the Rate Constant During Polymerizationmentioning

confidence: 99%

“…6 for sϭ10 6 and c ϭ0.01 c , and different values of Pe. The relative rate constant increases with increasing Pe number as found above, and shows a power law dependence.…”

Section: A Parametric Studymentioning

confidence: 99%

“…Most previous studies report slowing down of the polymerization reaction due to diffusion control. [3][4][5][6] The role of flow on the step growth polymerization of rodlike polymers has been systematically studied in only a few previous works, though the benefits of stirring have been noted in several studies. 3,5,7 Agarwal and Khakhar 8,9 synthesized poly͑p-phenylene terepthalamide͒ ͑PPDT͒ in a two-reactor system in which the monomers were mixed in a solvent in reactor I by means of high speed stirring and then transferred to reactor II, a concentric cylinder system which produced a uniform shear flow in the gap between the cylinders.…”

Section: Introductionmentioning

confidence: 99%

“…Predictions of the model were compared to experimental data for PPDT polymerization. 6 The model gave a length ͑L͒ and concentration ͑C͒ dependence of the effective rate constant of the form…”

Section: Introductionmentioning

confidence: 99%

“…6 Gupta and Khakhar 19 used pairwise Brownian dynamics instead of the finite element method for computing the rate constant for rodlike molecules. This method is very simple to implement, however, it is computationally intensive.…”

Section: Introductionmentioning

confidence: 99%

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Flow enhanced diffusion-limited polymerization of rodlike molecules

Jain

Agge

Khakhar

2001

The Journal of Chemical Physics

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Polymerization of rigid rodlike molecules with reactive end groups requires near parallel orientation of the molecules. The reaction is diffusion limited because of the low mobility of the molecules in the later stages of the reaction. Experimental studies have shown that flow-induced molecular orientation enhances the rate of polymerization ͓Agarwal and Khakhar, Nature 360, 53 ͑1992͔͒. Here a theoretical study of the polymerization under axisymmetric extensional flow is carried out to obtain the effective reaction rate constant (k eff ) for the reaction. Computations show that an increase in the intrinsic rate constant (k h ) results in a decrease in the relative rate constant k rel ϭk eff /k h . Reduction in the rotational diffusivity (D r ) results in a significant reduction in k rel ; however, the variation of the translational diffusion coefficient perpendicular to the rod axis D Ќ has only a small effect for D Ќ /D ʈ Ӷ1, where D ʈ is the diffusivity parallel to the rod axis. The imposition of flow increases the effective rate constant, however, the variation of k rel with other parameters remains qualitatively similar at different Peclet numbers (Peϭ /D r , where is the extensional rate͒. To simulate the variation of the rate constant during polymerization, computations are carried out for different rod lengths using correlations to estimate rod diffusivities. Results indicate that k rel initially decreases and then increases after a certain critical degree of polymerization, which reduces with increase in Peclet number. For sufficiently high extensional rates ( ϳ200 s Ϫ1 ) the rate constant becomes higher than the intrinsic value (k rel Ͼ1).

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Section: B Variation Of the Rate Constant During Polymerizationmentioning

confidence: 99%

“…6 for sϭ10 6 and c ϭ0.01 c , and different values of Pe. The relative rate constant increases with increasing Pe number as found above, and shows a power law dependence.…”

Section: A Parametric Studymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Flow enhanced diffusion-limited polymerization of rodlike molecules

Jain

Agge

Khakhar

2001

The Journal of Chemical Physics

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Preparation and performance of aramid nanofiber membrane for separator of lithium ion battery

Tian

Yan

et al. 2016

J of Applied Polymer Sci

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Stable and uniform dispersions of para-aramid nanofibers have been prepared by adding methoxypolyethylene glycol (mPEG) in the polymerization process, followed by strong shear and dispersion. Aramid membranes are fabricated by vacuumassisted filtration of the nanofiber dispersion and assembled into batteries as separator. The membrane properties and battery performances are characterized in detail and the effect of mPEG content on these properties is explored. It is demonstrated that aramid membranes possess good electrolyte wettability, excellent mechanical properties, and superior thermal stability, which improve the safety of lithium ion batteries. The mPEG is critical to the formation of aramid nanofibers and improves the porosity and ionic conductivity of the membranes. These fascinating characteristics and facile papermaking method endow aramid membrane potential application as separator in lithium ion batteries with superior safety.

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Dynamic Urea Bond‐Mediated Polymerization for Solvent‐Free Low‐Ð Linear Polyurethanes of Controlled Molar Mass: Hypothesis of Diffusion Control

Fonseca

2022

Macro Chemistry & Physics

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Dynamic urea bond-mediated polymerization (DUBMP) has been employed for the synthesis of linear, branched, telechelic, and random-block polyurethanes (PUs) with low molar-mass dispersity relative to conventionally synthesized PUs (Ð < 1.5). However, the reason for the improved control of the molar mass and reduction in dispersity, promoted by DUBMP, has not been explained. In this paper, the DUBMP synthesis of linear PU based on low-molar-mass poly(ethylene glycol) (PEG) and isophorone diisocyanate is studied comprehensively. The lower viscosity of the PEG-based PU allows DUBMP to reach high conversions (≈0.97) for the first time, while molar mass and Ð vary substantially with reaction conditions, despite yielding similar/equal conversion values. Both molar mass and Ð increase with an increase in reaction temperature, or with a reduction of the amine/isocyanate molar ratio. Therefore, evidence suggests that DUBMP provides diffusion control due to the lower mobility of the longer chains associated with an isocyanate-deactivator-rich environment. An increase in the reaction temperature, and/or a decrease in the amine/isocyanate molar ratio, reduces the diffusion control, leading to higher Ð values and molar mass. Tuning of the reaction conditions allows obtaining PU of controlled molar mass (11 kDa ≤ M w ≤ 42 kDa) and 1.3 < Ð < 1.75.

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Polymerization kinetics of rodlike molecules under quiescent conditions

Cited by 13 publications

References 24 publications

Flow enhanced diffusion-limited polymerization of rodlike molecules

Flow enhanced diffusion-limited polymerization of rodlike molecules

Preparation and performance of aramid nanofiber membrane for separator of lithium ion battery

Dynamic Urea Bond‐Mediated Polymerization for Solvent‐Free Low‐Ð Linear Polyurethanes of Controlled Molar Mass: Hypothesis of Diffusion Control

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