A Review on Polymer Crystallization Theories

Zhang, Michael C.; Guo, Baohua; Xu, Jun

doi:10.3390/cryst7010004

Cited by 136 publications

(122 citation statements)

References 188 publications

(227 reference statements)

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“…Another important aspect of polymer crystallization is the mechanism of nucleation and growth under nonisothermal condition. Under nonisothermal conditions, the temperature of the system continuously reduces; hence, we could envisage several events that occur more or less simultaneously . If the nucleation event is fast enough relative to the rate of cooling, then there is a finite probability that new lamellae of different thicknesses form at different temperatures during cooling.…”

Section: Discussionmentioning

confidence: 99%

A General Approach for Estimating Lamella‐Thickness Distribution in Polymers with Low‐Frequency Raman Spectroscopy: Application to Lamella Formation in Crystallizing Polyethylene

Samuel

Hamaguchi

2018

Chemistry A European J

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A general method for estimating lamella-thickness distribution in semicrystalline polymers has been developed and applied to polyethylene (PE). The longitudinal acoustic mode (LAM) of PE appears at very low frequencies (i.e., ν˜ 8-20 cm ) in the Raman spectrum. It represents a distribution of lamellae of varying thicknesses. We propose a distribution function that converts a low-frequency LAM Raman band into the corresponding lamellae-thickness distribution. By using this distribution function, we can study lamella formation in crystallizing PE to elucidate the influence of supercooling and determine critical lamella thickness, the minimum chain length at which folding occurs, and the associated thermodynamic parameters accurately. This method has a general applicability toward the examination of polymer crystallization in an accurate and straightforward manner. Understanding the molecular details of polymer crystallization has applications, particularly in polymer thin-film photovoltaics and polymer processing, beyond its fundamental academic significance.

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Section: Discussionmentioning

confidence: 99%

A General Approach for Estimating Lamella‐Thickness Distribution in Polymers with Low‐Frequency Raman Spectroscopy: Application to Lamella Formation in Crystallizing Polyethylene

Samuel

Hamaguchi

2018

Chemistry A European J

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“…The free energy of the formation of this crystal from solution can be expressed as

Δ G = 2 σ_{1} L_{2} L_{3} + 2 σ_{2} L_{1} L_{3} + 2 σ_{3} L_{1} L_{2} - ((), \frac{L_{1}}{d_{1}} - 1) ε_{1} L_{2} L_{3} - ((), \frac{L_{2}}{d_{2}} - 1) ε_{2} L_{1} L_{3} - ((), \frac{L_{3}}{d_{3}} - 1) ε_{3} L_{1} L_{2}

…”

Section: Mechanism Of Conjugated Polymer Crystallizationmentioning

confidence: 99%

“…For a fixed crystal volume, the length of the crystal in the three directions can be expressed as

\frac{L_{1}}{2 σ_{1} + ε_{1}} = \frac{L_{2}}{2 σ_{2} + ε_{2}} = \frac{L_{3}}{2 σ_{3} + ε_{3}}

…”

Section: Mechanism Of Conjugated Polymer Crystallizationmentioning

confidence: 99%

Conjugated polymer single crystals and nanowires

Cao

Zhao

Liang

et al. 2019

Polymer Crystallization

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Conjugated polymer single crystals and nanowires show advantages for the study of intrinsic charge transport in conjugated polymers and achieve high device performance. However, preparation of conjugated polymer single crystals and nanowires, especially donor‐acceptor (D‐A) conjugated polymers, is challenging. In this review, the structural features of conjugated polymers are first described. Then, the mechanism of conjugated polymer crystallization in terms of thermodynamic equilibrium state, nucleation, and growth is discussed. Single crystals of poly(alkylthiophene)s (P3ATs) and nanowires of both P3ATs and D‐A conjugated polymers are subsequently reviewed. Growth kinetics are a key issue in growing D‐A‐conjugated polymer crystals. Finally, the device performance based on conjugated polymer single crystals and nanowires is summarized.

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“…The latter usually occurs during the crystal growth process and determines the growth rate. If the crystal growth process adopts the surface nucleation mechanism, formation of the critical secondary nuclei with the highest Gibbs free energy acts as the rate-determining step during the crystal growth process [5][6][7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Critical Size of Secondary Nuclei Determined via Nucleation Theorem Reveals Selective Nucleation in Three-Component Co-Crystals

Gao

Guo

2019

Entropy

Self Cite

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The critical size of the secondary nuclei plays an important role in determining the crystal growth rate. In the past, the Nucleation Theorem has been applied to determine the number of molecules in the critical nuclei of a single-component crystal via variation of the crystal growth rate with dilution by the non-crystallizable component. In this work, we extend the method to the three-component co-crystal poly (ethylene oxide)/urea/thiourea inclusion compound. The theoretical crystal growth kinetics were deduced and the dependence of the radial growth rate of the inclusion compound spherulites on the mass fraction of urea in urea/thiourea was measured. The results reveal that the secondary nuclei of the poly (ethylene oxide)/urea/thiourea inclusion compound consist mainly of ethylene oxide repeating units and urea molecules. We propose that only urea molecules and ethylene oxide repeating units are selected to form the secondary nuclei while co-crystallization of the three components happens at the lateral spreading stage. As a result, the composition of the critical secondary nuclei is different from that of the bulk inclusion compound crystals. The work is expected to deepen our understanding of the nucleation of multi-component co-crystals.Entropy 2019, 21, 1032 2 of 12 compound (IC) during its crystal growth process [17]. The PEO/urea ICs consist of guest PEO chains residing in the cavities formed by the host urea molecules [18][19][20][21][22][23][24][25][26]. By replacing a small amount of urea with N,N -dimethyl urea with the PEO concentration unchanged, we could change the rate of secondary nucleation and determine the critical size of the secondary nuclei of the PEO/urea IC β crystal. Here, dimethylurea acted as a dilute agent, which was completely precluded from the crystal lattice. In the PEO/urea IC β crystal, the fixed stoichiometric ratio of 3/2 exists between ethylene oxide (EO) repeating units and urea molecules [22][23][24]27]; the crystallization unit is an entity containing 1 urea and 1.5 EO repeating units. Taking an entity as a unit of crystallization, the inclusion compound can be simplified as one-component crystal. A power-law relationship between the radial growth rate G and the mass fraction x of urea in the total mass of urea and the diluent was observed, and the exponent gave the critical size of the secondary nucleus. Our results revealed that a critical secondary nucleus of the PEO/urea IC β crystal consisted of 4 to 9 entities in the studied temperature range [17].In this work, we attempt to extend the Nucleation Theorem to determine the critical size of the secondary nuclei in a three-component co-crystal system poly (ethylene oxide)/urea/thiourea inclusion compound. Thiourea is an analogue molecule of urea, and as a result, the three components co-crystallize. PEO/urea/thiourea IC prepared by electrospinning was reported by Ye et al. [28], but the crystal growth kinetics were not examined. Here we find that the spherulites of PEO/urea/thiourea IC can form by isothermal crystalliz...

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A Review on Polymer Crystallization Theories

Cited by 136 publications

References 188 publications

A General Approach for Estimating Lamella‐Thickness Distribution in Polymers with Low‐Frequency Raman Spectroscopy: Application to Lamella Formation in Crystallizing Polyethylene

A General Approach for Estimating Lamella‐Thickness Distribution in Polymers with Low‐Frequency Raman Spectroscopy: Application to Lamella Formation in Crystallizing Polyethylene

Conjugated polymer single crystals and nanowires

Critical Size of Secondary Nuclei Determined via Nucleation Theorem Reveals Selective Nucleation in Three-Component Co-Crystals

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