Role of Thermal History and Entanglement Related Thickness Selection in Polymer Crystallization

Luo, Chuanfu; Sommer, Jens‐Uwe

doi:10.1021/acsmacrolett.5b00668

Cited by 98 publications

(120 citation statements)

References 40 publications

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“…Other sources of self‐nucleation can be found in melts at temperatures a few degrees above the observed melting point. For example, it has been posited that self‐nuclei may derive from residual orientation of chain segments that formed the initial crystallites, from residual intermolecular interactions, from a heterogeneous distribution of crystalline sequences or from inhomogeneous entanglement redistribution …”

Section: Introductionmentioning

confidence: 99%

“…For example, it has been posited that self-nuclei may derive from residual orientation of chain segments that formed the initial crystallites, [4][5][6] from residual intermolecular interactions, 7-9 from a heterogeneous distribution of crystalline sequences [10][11][12][13][14] or from inhomogeneous entanglement redistribution. 15,16 In homopolymers, the memory effect is mostly observed below the equilibrium melting temperature and near the observed melting resulting in higher crystallization temperatures or higher rates of crystallization, smaller spherulites and even modifications of the crystal lattice in systems that display polymorphism. 1,[17][18][19][20][21][22][23][24] Below the equilibrium melting temperature, the polymer melt is undercooled and the possibility of crystallites surviving in the melt cannot be excluded.…”

Section: Introductionmentioning

confidence: 99%

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Effect of annealing time and molecular weight on melt memory of random ethylene 1‐butene copolymers

Chen

Alamo

2018

Polymer International

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The effects of annealing time and molecular weight on the strong melt memory effect observed in random ethylene 1‐alkene copolymers are analyzed in a series of model ethylene 1‐butene copolymers with 2.2 mol% branches. Melt memory is associated with molten clusters of ethylene sequences from the initial crystals that remain in close proximity and are unable to diffuse quickly to the randomized melt state, thus increasing the recrystallization rate. Melt memory persists even for greater than 1000 min annealing indicating a long‐lived nature of the clusters that only fully dissolve at melt temperatures above a critical value (>160 °C). Below the critical melt temperature, molecular weight and annealing temperature have a strong influence on the slow kinetics of melt memory. For the copolymers analyzed, slow dissolution of clusters is experimentally observed only for Mw < 50 000 g mol−1. More stable clusters that survive higher annealing temperatures display slower dissolution rates than clusters remaining at lower temperatures. The threshold crystallinity level to enable melt memory (Xc,threshold) decreases with increasing molecular weight and decreasing annealing temperature similarly to the variation of the chain diffusivity in the melt. The process leading to melt memory is thermally activated as the variation of Xc,threshold with temperature follows Arrhenius behavior with high activation energy (ca 108 kJ mol−1) that is independent of molecular weight. © 2018 Society of Chemical Industry

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of annealing time and molecular weight on melt memory of random ethylene 1‐butene copolymers

Chen

Alamo

2018

Polymer International

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“…Simulations were performed using the coarse‐grained model of poly(vinyl alcohol) (CG‐PVA) developed originally by Meyer et al and successfully applied in multiple studies of polymer crystallization . In this model, each monomer is mapped into a single bead.…”

Section: Methodsmentioning

confidence: 99%

“…Simulations were performed using the coarse-grained model of poly(vinyl alcohol) (CG-PVA) developed originally by Meyer et al 30,[40][41][42] and successfully applied in multiple studies of polymer crystallization. 13,[15][16][17]43 In this model, each monomer is mapped into a single bead. Intramolecular degrees of freedom are described via harmonic bond interactions coupled with tabulated angle potentials with minima at t-t, g-t, and g-g configurations.…”

Section: Methodsmentioning

confidence: 99%

“…There have been several studies of polymer crystallization using molecular dynamics in order to predict the effect of parameters such as polymer chain length, bond bending stiffness or cooling protocol . Jabbarzadeh et al have compared the crystallization kinetics for two different chain lengths upon quiescent and pre‐stretched regimes using a united‐atom force field for polyethylene.…”

Section: Introductionmentioning

confidence: 99%

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Molecular dynamics simulations of monodisperse/bidisperse polymer melt crystallization

Triandafilidi

Rottler

Hatzikiriakos

2016

J. Polym. Sci. Part B: Polym. Phys.

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We use large scale coarse‐grained molecular dynamics simulations to study the kinetics of polymer melt crystallization. For monodisperse polymer melts of several chain lengths under various cooling protocols, we show that short chains have a higher terminal crystallinity value compared to longer ones. They align at the early stages and then cease evolving. Long chains, however, align, fold into lamella structures and then slowly optimize their dangling ends for the remaining simulation time. We then identify the mechanism behind bidisperse blend crystallization. To this end, we introduce a new algorithm (called Individual Chain Crystallinity) that allows the calculation of the crystallinity separately for short and long chains in the blend. We find that, in general, bidispersity hinders crystallization significantly. At first the crystallinity of the long chain components exceeds that of the monodisperse melt, but subsequently falls below the corresponding monodisperse melt curve after a certain “crossover time.” The time of the crossover can be attributed to the time required for the full crystallization of the short chains. This indicates that at the early stages the short chains are helping long chains to crystallize. However, after all short chains have crystallized they start to hinder the crystallization of the long chains by obstructing their motion. Lastly, polymer crystallization upon various thermodynamic protocols is studied. Slower cooling is found to increase the crystallinity value. Upon an instantaneous deep quench and subsequent isothermal relaxation, the crystallinity grows rapidly with time at early stages and subsequently saturates. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2318–2326

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A Single‐Crystal Monomer to Single‐Crystal Polymer Reaction Activated by a Triplet Excimer in a Zipper Mechanism

et al. 2023

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A combined experimental and theoretical study focused on the elucidation of the polymerization mechanism of crystal monomer to crystal polymer reaction of a bisindacene compound in the solid state has been carried out. The experimental description and characterization of the polymer product have been reported elsewhere and, in this article, we address the first detailed description of the polymerization process. This reaction pathway consists in the initial formation of a triplet excimer state that relaxes to a intermolecular bonded triplet state that is the starting point of the propagation step of the polymerization. The overall process can be visualized in the monomer starting state as an open zipper in which a cursor or slider is formed by light absorption and the whole zipper is then closed by propagation of the double cursor. To this end, variable‐temperature electron spin resonance, femtosecond transient absorption spectroscopy and vibrational Raman spectroscopic data have been implemented in combination with quantum chemical calculations. The presented mechanistic insight is of great value to understand the intricacies of such important reaction, and to envisage and diversify the products produced by it.

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Role of Thermal History and Entanglement Related Thickness Selection in Polymer Crystallization

Cited by 98 publications

References 40 publications

Effect of annealing time and molecular weight on melt memory of random ethylene 1‐butene copolymers

Effect of annealing time and molecular weight on melt memory of random ethylene 1‐butene copolymers

Molecular dynamics simulations of monodisperse/bidisperse polymer melt crystallization

A Single‐Crystal Monomer to Single‐Crystal Polymer Reaction Activated by a Triplet Excimer in a Zipper Mechanism

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