The supercooling dependence of the initial fold length of polyethylene crystallized from the melt: unification of melt and solution crystallization

Barham, Peter; Chivers, Robin A.; Keller, A.; Martínez‐Salazar, Javier; Organ, S. J.

doi:10.1007/bf00555265

Cited by 102 publications

(73 citation statements)

References 13 publications

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“…As with other crystalline polymers, the long spacing increases with the increase of annealing temperature. These features are also expected for chain-folded lamellar crystals [18,19].…”

Section: Introductionsupporting

confidence: 63%

Chain Folding of Main-Chain Polyesters in the Smectic A and CA Phases with a Liquid-Like Association of Biphenyl Mesogens within a Layer.

et al. 1999

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: The solid state morphology of poly (methylene p,p -bibenzoate) (BB-n) was studied by the small-angle X-ray scattering (SAXS) method. The BB-n polyesters with n of 6 and 8 form isotropic, smectic A, and crystal phases in the order of decreasing temperature; thereby their crystallization taking place from the smectic A phase. The SAXS for the crystalline specimens shows the well-defined reflection maxima which are attributable to the stacked lamellar structure. The lamellar spacings are distributed around 250 -300 A so that an appreciable number of chain foldings are included in a chain. The lamellar size is increased by annealing the crystal like in other crystalline polymers. In contrast, it is not essentially altered by annealing the preceding smectic A phase. Most interesting is that the lamellar spacing increases with a decrease in the crystallization temperature. The trend is contrary to that observed in conventional polymers as well as in BB-10 and BB-12 which crystallize from the isotropic melt and can be explained if in the preceding smectic A phase the chain foldings exist at a thermodynamic equilibrium as an entropy effect. Such a chain folding was also predicted from anomalous orientation of molecules in the fibers drawn from the smectic melt. In these fibers, the polymer chains align in a direction perpendicular to the fiber axis. This orientation is completely retained even if the fiber is further elongated up to the strain of 100%. These results suggest that the chain foldings take place at a limited space to form the lamellar smectic domain.

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“…As with other crystalline polymers, the long spacing increases with the increase of annealing temperature. These features are also expected for chain-folded lamellar crystals [18,19].…”

Section: Introductionsupporting

confidence: 63%

Chain Folding of Main-Chain Polyesters in the Smectic A and CA Phases with a Liquid-Like Association of Biphenyl Mesogens within a Layer.

et al. 1999

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“…39 In the limit L c → ∞ the recrystallization line and the crystallization line lead to the same temperature T ∞ c ≈ 182 • C. Note that here the initial thickness of the lamellae has been used for this plot (see the discussion of this point in ref. 43 ).…”

Section: B Variation Of Annealing Temperaturementioning

confidence: 99%

Annealing of Single Lamella Nanoparticles of Polyethylene

et al. 2011

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We study the change of the size and structure of freely suspended single lamella nanoparticles of polyethylene during thermal annealing in aqueous solutions. Using small-angle x-ray scattering and cryogenic transmission electron microscopy, it is shown that a doubling of the crystalline lamella sandwiched between two amorphous polymer layers is obtained by annealing the nanoparticles at 125 • C. This thickening of the crystalline lamella can be understood in terms of an unlooping of polymer chains within a single nanoparticle. In addition a variation of the annealing temperature from 90 • C to 115 • C demonstrates that the inverse of the crystalline lamellar thickness increases linearly with the annealing temperatures leading to a recrystallization line in a Gibbs-Thomson graph. Since the nanoparticles consist of about only eight polymer chains, they can be considered as a ideal candidates for the experimental realization of equilibrium polymer crystals.

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“…4 The first theory, which was formulated by Lauritzen and Hoffman ͑LH͒ soon after the initial discovery of the chainfolded crystals, [5][6][7] invokes surface nucleation of a new layer on the thin side faces of the lamellae as the key process. It assumes that there is an ensemble of crystals of different thickness, each of which grows with constant thickness.…”

Section: Introductionmentioning

confidence: 99%

Kinetic Monte Carlo simulations of the growth of polymer crystals

Doye

Frenkel

1999

The Journal of Chemical Physics

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Based upon kinetic Monte Carlo simulations of crystallization in a simple polymer model we present a new picture of the mechanism by which the thickness of lamellar polymer crystals is constrained to a value close to the minimum thermodynamically stable thickness, l min . The free energetic costs of the polymer extending beyond the edges of the previous crystalline layer and of a stem being shorter than l min provide upper and lower constraints on the length of stems in a new layer. Their combined effect is to cause the crystal thickness to converge dynamically to a value close to l min where growth with constant thickness then occurs. This description contrasts with those given by the two dominant theoretical approaches. However, at small supercoolings the rounding of the crystal profile does inhibit growth as suggested in Sadler and Gilmer's entropic barrier model.

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The supercooling dependence of the initial fold length of polyethylene crystallized from the melt: unification of melt and solution crystallization

Cited by 102 publications

References 13 publications

Chain Folding of Main-Chain Polyesters in the Smectic A and CA Phases with a Liquid-Like Association of Biphenyl Mesogens within a Layer.

Chain Folding of Main-Chain Polyesters in the Smectic A and CA Phases with a Liquid-Like Association of Biphenyl Mesogens within a Layer.

Annealing of Single Lamella Nanoparticles of Polyethylene

Kinetic Monte Carlo simulations of the growth of polymer crystals

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