Isothermal growth of low molecular weight polyethylene single crystals from solution. 1. Variation of equilibrium dissolution temperature with molecular weight and lamellar thickness with crystallization temperature

Leung, W. M.; Manley, R. St. John; Panaras, A. R.

doi:10.1021/ma00146a029

Cited by 31 publications

(16 citation statements)

References 9 publications

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“…The ability of all samples to form single crystals is noteworthy. Some common features already observed by other authors on single crystals of linear PE are also present in the micrographs of Figure . For example, crystals of uniform size are obtained, an indication that they have been self‐nucleated.…”

Section: Resultssupporting

confidence: 80%

“…The variations in shape, morphology, and structure of single crystals, particularly of linear PE, have been intensively studied by physicists for more than 50 years . A renewed interest in the study of linear PE single crystals in the last decade has appeared with the works by Organ et al, Tian et al, Nakamura et al, and Zhang et al However less attention has been paid to the case of branched PE.…”

Section: Introductionmentioning

confidence: 99%

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The influence of short-chain branching on the morphology and structure of polyethylene single crystals

Vega

Jargour

Núñez-Ramírez

et al. 2015

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

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The influence of short‐chain branching on the formation of single crystals at constant supercooling is systematically studied in a series of metallocene catalyzed high‐molecular‐weight polyethylene samples. A strong effect of short‐chain branching on the morphology and structure of single crystals is reported. An increase of the axial ratio with short‐chain branching content, together with a characteristic curvature of the (110) crystal faces are observed. To the best of our knowledge, this is the first time that this observation is reported in high‐molecular‐weight polyethylene. The curvature can be explained by a continuous increase in the step initiation—step propagation rates ratio with short‐chain branching, that is, nucleation events are favored against stem propagation by the presence of chain defects. Micro‐diffraction and WAXS results clearly indicate that all samples crystallize in the orthorhombic form. An increase of the unit cell parameter a0 is detected, an effect that is more pronounced than in the case of single crystals with ethyl and propyl branches. The changes observed are compatible with an expanded lattice due to the presence of branches at the surface folding. A decrease in crystal thickness with branching content is observed as determined from shadow measurements by TEM. The results are in agreement with additional SAXS results performed in single crystal mats and with indirect calorimetry measurements. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1751–1762

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Section: Resultssupporting

confidence: 80%

Section: Introductionmentioning

confidence: 99%

The influence of short-chain branching on the morphology and structure of polyethylene single crystals

Vega

Jargour

Núñez-Ramírez

et al. 2015

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

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“…Those general issues in polymer crystallization also appear in the subfield of solution crystallization. The equilibrium dissolution temperatures ( T

_{d}^{0}

's) of polyethylene (PE) in xylene have been carefully measured,22–24 and several theories have been developed to predict T

_{d}^{0}

25–28. However, inconsistencies between experimental results and theoretical predictions remain, as pointed out in previous24 and recent publications 29.…”

Section: Introductionmentioning

confidence: 99%

“…The equilibrium dissolution temperatures ( T

_{d}^{0}

's) of polyethylene (PE) in xylene have been carefully measured,22–24 and several theories have been developed to predict T

_{d}^{0}

25–28. However, inconsistencies between experimental results and theoretical predictions remain, as pointed out in previous24 and recent publications 29. On the other hand, the growth kinetics depend on the crystal habits and crystallographic directions;30, 31 a general mean field description of crystallization kinetics could be difficult 13…”

Section: Introductionmentioning

confidence: 99%

Time‐resolved small‐angle neutron scattering study of polyethylene crystallization from solution

Wang

2004

J Polym Sci B Polym Phys

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With time-resolved small-angle neutron scattering (TR-SANS), the crystallization kinetics of polyethylene from deuterated o-xylene solutions upon a temperature jump have been investigated. On the basis of a morphological model of coexisting lamellar stacks and coil chains in solution, experimental data have been quantitatively analyzed to provide structural information, such as the lamellar long period, the lamellar crystal thickness, the thickness of the amorphous layers between lamellae, the degree of crystallinity, and the crystal growth rate at various degrees of undercooling. The viability of TR-SANS for studying polymer crystallization is demonstrated through the consistency of these measurements and well-established knowledge of polyethylene crystallization from xylene solutions. One unique feature of this experimentation is that both the growth of lamellar crystals and the condensation of coil chains from solution are monitored simultaneously. The ratio of the crystal growth to the chain consumption rate decreases rapidly with a decreasing degree of undercooling. The Avrami analysis suggests that the growth mechanism approaches two-dimensional behavior at higher temperatures, and this is consistent with the observation of an increasing ratio of the sharp-surface area to the bulk crystal growth rate with temperature. The limitations, possible remedies, and potentials of TR-SANS for studying polymer crystallization are discussed.

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“…Because of the crystals' tendency to recrystallize after melting on slow heating, the T m of PE single crystals cannot be easily obtained directly 10. At the typical heating rates (10–20 K/min) employed in macroscale DSC, there is no simple correlation between the measured T m and the properties of the original material.…”

Section: Introductionmentioning

confidence: 99%

Nanoscale calorimetry of isolated polyethylene single crystals

Kwan

Efremov

Olson

et al. 2001

J Polym Sci B Polym Phys

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ABSTRACT:We used thin-film differential scanning calorimetry to investigate the melting of isolated polyethylene single crystals with lamellar thicknesses of 12 Ϯ 1 nm. We observed the melting of as few as 25 crystals. Over a wide number of crystals (25-2000 crystals), the heat of fusion was 40% larger than the bulk value. The melting temperature of the isolated single crystals was 123 Ϯ 2°C, 9°C lower than that of the bulk material. We also measured the heat of fusion of quenched crystals (Ϯ15%) over a wide range of heating rates (20,000 -100,000 K/s). Annealing the quenched crystals resulted in shifts in the endotherm peak by as much as 15°C.

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Isothermal growth of low molecular weight polyethylene single crystals from solution. 1. Variation of equilibrium dissolution temperature with molecular weight and lamellar thickness with crystallization temperature

Abstract: Note that these matrix elements are appropriate to the case that the doublet-state species be sensitized to an excited state.

Cited by 31 publications

References 9 publications

The influence of short-chain branching on the morphology and structure of polyethylene single crystals

The influence of short-chain branching on the morphology and structure of polyethylene single crystals

Time‐resolved small‐angle neutron scattering study of polyethylene crystallization from solution

Nanoscale calorimetry of isolated polyethylene single crystals

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