Polymorphism and side group location of ethylene copolymers characterized by FTIR and NMR spectroscopy

Su, Zhiqiang; Zhao, Ying; Xu, Yizhuang; Zhang, Xiuqin; Zhu, Shifan; Wang, Dujin; Han, Charles C.; Xu, Duanfu

doi:10.1016/j.polymer.2004.03.076

Cited by 9 publications

(8 citation statements)

References 18 publications

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“…Two large endothermic peaks that correspond to the melting of two different crystalline species are seen. The high‐temperature one at 80 °C is due to the melting of LOCP crystal, which is consistent with the previous result 29. The low‐temperature endothermic peak is attributed to the melting of SOCP crystal rather than the melting of the MCP crystal.…”

Section: Resultssupporting

confidence: 91%

“…Such a low‐temperature melting is related to SOCP or LOCP, because the total 32.9 ppm peak is from overlapping of the rigid LOCP and mobile SOCP components. Considering that the melting of rigid LOCP occurs at higher temperature (∼80 °C) from previous study on EVA29 and our DSC measurement ( vide infra ), this low‐temperature melting is ascribed to SOCP. By measuring the intensities of 32.9 ppm peak at 25 and 50 °C in Figure 12(b), SOCP fraction of total LOCP and SOCP components is calculated as 40%, in approximate consistence with fraction estimated from T 1 data.…”

Section: Resultssupporting

confidence: 51%

“…In the previous NMR investigations on EVA copolymers, only room‐temperature NMR spectra, combined with low‐temperature (∼−195 °C) Fourier transform infrared (FTIR) spectra were used to determine the structures of the samples 20, 29, 30. It was found that besides the normal orthorhombic crystalline and amorphous phases, a substable monoclinic crystal also appears at a higher VA content and it gradually transforms to an orthorhombic crystal with increasing annealing temperature.…”

Section: Introductionmentioning

confidence: 99%

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Solid‐state NMR characterizations on phase structures and molecular dynamics of poly(ethylene‐co‐vinyl acetate)

Wang

Fang

et al. 2006

J Polym Sci B Polym Phys

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Solid-state nuclear magnetic resonance spectroscopy and relaxation measurements, together with DSC, have been used to elucidate the structures and molecular dynamics in poly(ethylene-co-vinyl acetate) (EVA). It has been found that besides immobile orthorhombic and monoclinic crystalline phases, the third mobile crystalline phase (possibly the phase) of a considerable amount (36% of total crystalline phases) appears in the EVA samples, which forms during room-temperature aging as a result of the secondary crystallization and melts at temperature somewhat higher than room temperature. Such a mobile crystalline phase has not only the well-defined chemical shift of its own, but also has different molecular mobility from the orthorhombic phase. The mobile crystalline phase is characterized by the rapid relaxation of the longitudinal magnetization, which is caused by conventional spin-lattice relaxation, while the slow relaxation of the longitudinal magnetization occurring in the orthorhombic phase is originated from the chain diffusion. In addition, the amorphous phase also contains two components: an interfacial amorphous phase and a melt-like amorphous phase.

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Section: Resultssupporting

confidence: 91%

Section: Resultssupporting

confidence: 51%

Section: Introductionmentioning

confidence: 99%

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Solid‐state NMR characterizations on phase structures and molecular dynamics of poly(ethylene‐co‐vinyl acetate)

Wang

Fang

et al. 2006

J Polym Sci B Polym Phys

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“…In the past two decades, many investigations have been focused on the dependence of crystalline phases on side groups and on the role of thermal and processing history in the formation of crystalline phases in ethylene copolymers. − In general, a two-crystal model, say, e.g., longer ethylene sequences tend to crystallize into orthorhombic phase (OCP) and shorter ones tend to crystallize into monoclinic phase (MCP), is widely accepted for the long branch copolymers by assuming that the long branches cannot be incorporated in the crystal lattice . As for the copolymers with small side groups such as methyl of ethylene−propylene (EP), these short side groups can be incorporated into crystallites because of their small size and thus drive the change of the orthorhombic lattice toward a hexagonal/rotator crystalline phase (RCP) instead of the monoclinic phase, like the case of shorter n -alkanes. ,, …”

Section: Introductionmentioning

confidence: 99%

Crystalline Phases in Ethylene Copolymers Studied by Solid-State NMR and DSC

et al. 2010

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The structures and thermal properties of the multiple ordered phases in ethylene−octene and ethylene−butene copolymers have been studied using a combination of solid-state NMR and DSC. Three types of the ordered phases, namely the orthorhombic, monoclinic, and rotator (or ordered mobile phase), have been found to coexist in these two ethylene copolymers. Our experimental results demonstrate that the slow-spinning solid-state CP/MAS 13C NMR provides a convenient method to discern the NMR signals of the three different ordered phases and to measure the 13C chemical shift tensors of orthorhombic and monoclinic phases. The measurements of 13C chemical shift tensors and magnetic relaxation times show that monoclinic and orthorhombic crystal phases have similar chemical shift anisotropy with 180° flip-flop segmental movement. The chemical shift anisotropy and segmental mobility in the rotator phase, on the other hand, are different from those in the orthorhombic and monoclinic phases. DSC results illustrate that a low-melting-point phase forms during room-temperature aging and melts at temperature slightly above the room temperature. The apparent correlation between the low-melting-point phase and the rotator structure is revealed by a combination of variable-temperature solid-state CP/MAS NMR spectra with a slow-spinning rate and DSC measurement. It is thus suggested that the rotator formation induced by room-temperature aging is a common phenomenon for the ethylene copolymers with different sizes of side groups.

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“…FTIR spectroscopy, which is considered as a powerful tool for the characterization of crystal lattice vibration of polyolefins, can provide abundant structural information at molecular level and has received wide attention 12–28. Previous investigation showed that there are two molecular chains in each orthorhombic unit cell of polyethylene, and the methylene rocking bands split into doublet peaks at 720–730 cm −1 .The deformation of orthorhombic crystal lattice of polyethylene can be characterized quantitatively by the variation of peak positions, half‐widths, as well as the ratio of integrated area at 720 and 730 cm −1 bands.…”

Section: Introductionmentioning

confidence: 99%

Measurement of the variation of crystal lattice structures of ethylene copolymers with high‐resolution cryogenic FTIR spectroscopy

Su¹,

Li²,

Cao³

et al. 2011

J of Applied Polymer Sci

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High-resolution cryogenic Fourier transform infrared spectroscopy (FTIR) was used to measure the variation of the unit cell volume of ethylene-octene copolymers (EG) in this study. It was found that both the comonomer content and thermal history have great influence on the crystal lattice structure of ethylene polymers. With the increase of the octene content, the unit cell volume of EG copolymers expand, and quenching treatment favors the increase of distance between two molecular chains in orthorhombic crystals and causes more crystal lattice deformation. Compared with traditional wide-angle X-ray diffraction method, high-resolution cryogenic FTIR spectroscopy, as a powerful technique for measuring the changes of crystal lattice structures of polyethylene and ethylene copolymers, can provide more accurate information on the characterization of the changes of crystal lattice structures of semicrystalline polymers.

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Polymorphism and side group location of ethylene copolymers characterized by FTIR and NMR spectroscopy

Cited by 9 publications

References 18 publications

Solid‐state NMR characterizations on phase structures and molecular dynamics of poly(ethylene‐co‐vinyl acetate)

Solid‐state NMR characterizations on phase structures and molecular dynamics of poly(ethylene‐co‐vinyl acetate)

Crystalline Phases in Ethylene Copolymers Studied by Solid-State NMR and DSC

Measurement of the variation of crystal lattice structures of ethylene copolymers with high‐resolution cryogenic FTIR spectroscopy

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