A description of melting and crystallization of eutectic oligomers and copolymers — an application of the physical concepts of colloids

Kilian, H. G.

doi:10.1016/s0040-6031(94)85209-x

Cited by 9 publications

(6 citation statements)

References 72 publications

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“…A one-to-one correspondence of crystallite thickness to a critical sequence length was implied, depending only on the crystallization temperature. Sequences of the lengths longer than the critical value were supposed to crystallize without chain folding. , However, the diffusion of polymer chains is difficult in a viscous and crystallizing liquid. Therefore, a complete selection of sequence lengths at the crystal growth front will never be realized.…”

Section: Resultsmentioning

confidence: 99%

Sequence-Length Segregation during Crystallization and Melting of a Model Homogeneous Copolymer

Mathot

2003

Macromolecules

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Section: Resultsmentioning

confidence: 99%

Sequence-Length Segregation during Crystallization and Melting of a Model Homogeneous Copolymer

Mathot

2003

Macromolecules

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“…During cooling, the thermodynamic segregation according to the sequence length might be true in the local amorphous regions; 57 i.e., there may exist a local thermodynamic segregation according to the sequence length. 57 This might be true in the local amorphous regions, where short-range diffusion, even at the lowest temperatures, facilitates sequence selection for crystal growth. This is similar to the case of cold crystallization where only the nearest neighbors perform crystallization.…”

Section: Discussionmentioning

confidence: 99%

“…Since the absolute crystallinity realized at the lowest temperatures (see Figures b and a) is not sensitive to the comonomer content in the case of homogeneous copolymers, all of the monomer sequences seem to have the same chance to be finally included into (poor) crystalline regions. During cooling, the thermodynamic segregation according to the sequence length might be true in the local amorphous regions; i.e., there may exist a local thermodynamic segregation according to the sequence length . This might be true in the local amorphous regions, where short-range diffusion, even at the lowest temperatures, facilitates sequence selection for crystal growth.…”

Section: Discussionmentioning

confidence: 99%

Phase Transitions of Bulk Statistical Copolymers Studied by Dynamic Monte Carlo Simulations

Mathot

Frenkel

2003

Macromolecules

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We report a numerical study of crystallization and melting in bulk statistical homogeneous (random), homogeneous (slightly alternating), and heterogeneous (produced in a batch reaction) copolymers formed by crystallizable monomers and noncrystallizable comonomers. In our dynamic Monte Carlo simulations of lattice chains, the current model further assumes that the comonomers cannot move into crystalline regions by sliding diffusion of the chains. We find that both the overall composition and the statistical distribution of the monomers affect the phase-transition temperature, the resulting relative crystallinity, and the crystal morphology. However, the final absolute crystallinity of homogeneous copolymers seems insensitive to these parameters. Intramolecular segregation between monomers and comonomers is accompanied by crystallization, demonstrating the concept of sequence segregation or nanophase separation of statistical copolymers with assembling structures like in thermoplastic elastomers. Moreover, if crystallization of homogeneous copolymers has started but not yet completed on cooling, subsequent heating will show cold crystallization before melting, which can be attributed to insertion-mode lamellar growth. For heterogeneous copolymers, intermolecular segregation occurs on cooling before crystallization. On the basis of our observations, a pair of master melting and crystallization curves for the crystallinity of a statistical copolymer as a function of temperature are suggested to reflect the characteristic of the monomer-sequence-length distribution. This suggestion facilitates the clarification to the kinetic disturbance in local temperature regions and to the principle of some fractionation methods, such as temperature rising elution fractionation (TREF).

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“…The problem of extended chain crystals of such oligomers has been treated by Kilian and extended by him to copolymers and crosslinked systems. 37 In these cases, extended chain crystalline lamellae are formed, each of them being considered as an autonomous microphase. These lamellae are bordered by defect boundaries with lower densities than the crystal core.…”

Section: Discussionmentioning

confidence: 99%

Thermal behavior of poly(hexamethylene terephthalate) oligomers. I. Melting behavior and morphology of the crystalline phase

Lefebvre

Koch

Reynaers

et al. 1999

J. Polym. Sci. B Polym. Phys.

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The thermal behavior of poly(hexamethylene terephthalate) (PHT) oligomers containing variable amounts of isophthalic (IPA) monomer has been investigated. Poly(hexamethylene terephthalate‐co‐isophthalate) 3400 was first studied. This polymer has a Mn of 3400, is constituted by heterodisperse PHT units (crystallizable units) with a Mn of 2000, contains an average number of 2.6 IPA per chain, and has carboxylic chain ends. DSC results have shown that this polymer exhibits multiple melting endotherms. These are described in terms of (i) the existence of two melting zones located on both sides of Tc and associated with two polymer fractions differentiated by their crystallizable unit length, (ii) different crystalline populations growing at Tc, (iii) a reorganization process. A simultaneous small (SAXS) and wide (WAXS) angle time resolved X‐ray scattering study using synchrotron radiation has revealed that the different crystalline populations are characterized by different lamellar structures rather than by different crystalline lattices. Other PHTcoIs and PHTs differing from PHTcoI 3400 by their molecular weight and IPA content were also studied using DSC. IPA acts as a defect for crystallinity and causes Tm and ΔHm depression in the PHTcoIs. When the molecular weight of PHT increases, Tm increases and ΔHm decreases as usually reported in the literature. Finally, two crosslinked polymers (PHTcoI 3400 and PHTcoI 4700) were investigated. The insoluble fraction of crosslinked PHTcoI 3400 does not crystallize anymore while the one of PHTcoI 4700 does. This results from shorter crystallizable units and from the distance between the crosslinks of the former. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1–18, 1999

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A description of melting and crystallization of eutectic oligomers and copolymers — an application of the physical concepts of colloids

Cited by 9 publications

References 72 publications

Sequence-Length Segregation during Crystallization and Melting of a Model Homogeneous Copolymer

Sequence-Length Segregation during Crystallization and Melting of a Model Homogeneous Copolymer

Phase Transitions of Bulk Statistical Copolymers Studied by Dynamic Monte Carlo Simulations

Thermal behavior of poly(hexamethylene terephthalate) oligomers. I. Melting behavior and morphology of the crystalline phase

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