Molecular Orientation in Polyester Films Using Polarized Laser Raman and Fourier Transform Infrared Spectroscopies and X-Ray Diffraction

Voyiatzis, George A.; Petekidis, George; Vlassopoulos, Dimitris; Kamitsos, E. I.; Bruggeman, Albert

doi:10.1021/ma951199g

Cited by 34 publications

(45 citation statements)

References 38 publications

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“…This has also been reported for several other LCPs. 4,11,[46][47][48] One explanation put forward in literature for this discrepancy between the WAXS data and the results from other techniques invokes the easy rotation of the already existing domains. 11,48 Another explanation takes into account the nonisotropic orientation distribution at the capillary exit.…”

Section: Discussionmentioning

confidence: 95%

Determination of Orientation in Thermotropic Liquid Crystalline Polymer Films by Spectrographic Measurement of the Birefringence

Beekmans

Boer

1996

Macromolecules

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The degree of orientation in thermotropic liquid crystalline polymer films has been determined as a function of the draw ratio using a specially developed spectrographic birefringence technique, diffuse reflectance infrared spectroscopy (DRIFT), and wide-angle X-ray scattering (WAXS). Quantitative measurements of the average birefringence were obtained despite the huge turbidity of the samples. The order parameter calculated from the birefringence was found to depend on the draw ratio according to the Kuhn and Grü n equation for pseudo-affine deformation. The infrared dichroism was measured as a function of film thickness by layer removal. The thickness-averaged orientation calculated from the DRIFT measurements also indicated affine deformation of the films. The orientation derived from WAXS appeared to be clearly overaffine. The difference between the results from WAXS and the results from the other two techniques is attributed to preferential orientation of the crystalline fraction due to flow-induced crystallization in the films which is detected only by WAXS.

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Section: Discussionmentioning

confidence: 95%

Determination of Orientation in Thermotropic Liquid Crystalline Polymer Films by Spectrographic Measurement of the Birefringence

Beekmans

Boer

1996

Macromolecules

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“…The transition moment directions of both bands are parallel to the chain backbone direction, and they all exhibit the parallel dichroism. During stretching, the variations of second-order orientation parameters [33] (P 2 ) of UE-IR units are shown in Figure 2b. It is clear that, at low strain with ε = 1, the P 2 value of ENR-40 is the highest, while the ENR-25 and NR exhibit a similar P 2 value.…”

Section: Natural Rubbermentioning

confidence: 99%

The Effect of Epoxidation on Strain‐Induced Crystallization of Epoxidized Natural Rubber

Zhang

Niu

Song

et al. 2019

Macromol. Rapid Commun.

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The effect of epoxidation on strain‐induced crystallization (SIC) of epoxidized natural rubber (ENR) and mechanism are studied with synchrotron radiation wide‐angle X‐ray diffraction (SR‐WAXD) and polarized infrared spectroscopy (P‐IR). WAXD results reveal that appropriate epoxidation, for example, ENR‐25 epoxidized with ≈25% isoprene units, can unexpectedly enhance the SIC of natural rubber (NR), resulting in the improvement of tear resistance. On the other hand, exorbitant epoxidation, for example, ENR‐40 epoxidized with ≈40% isoprene units, depresses the SIC and weakens the mechanical properties of NR remarkably. P‐IR studies reveal that epoxidation can promote the orientation of chain segments along the stretching direction, which plays a determining role on SIC of NR. Accordingly, hierarchical multiscale schematic models are proposed. This insight into epoxidation on SIC of ENR strongly suggests that ENR with appropriate epoxidation degree is a promising candidate material for the fabrication of high‐performance engineering rubber products.

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“…In principle, an estimation of the orientation of the fibrils could be obtained from the intensity ratio from this band, applying the expressions derived by Bower. 65 Although this method has been employed extensively for a number of systems, [66][67][68][69] certain assumptions on the symmetry of the Raman tensor are needed in order to solve the equations involved. Moreover, the information polarised Raman scattering experiments can give about f (b) is limited to the first two moments of its Legendre expansion (P 2 and P 4 ).…”

Section: X-ray Diffractionmentioning

confidence: 99%

Determination of orientations of aromatic groups in self-assembled peptide fibrils by polarised Raman spectroscopy

Rodríguez‐Pérez

Hamley

Squires

2013

Phys. Chem. Chem. Phys.

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In this paper we describe a novel combination of Raman spectroscopy, isotope editing and X-ray scattering as a powerful approach to give detailed structural information on aromatic side chains in peptide fibrils. The orientation of the tyrosine residues in fibrils of the peptide YTIAALLSPYS with respect to the fibril axis has been determined from a combination of polarised Raman spectroscopy and X-ray diffraction measurements. The Raman intensity of selected tyrosine bands collected at different polarisation geometries is related to the values and orientation of the Raman tensor for those specific vibrations. Using published Raman tensor values we solved the relevant expressions for both of the two tyrosine residues present in this peptide. Ring deuteration in one of the two tyrosine side chains allowed for the calculation to be performed individually for both, by virtue of the isotopic shift that eliminates band overlapping. Sample disorder was taken into account by obtaining the distribution of orientations of the samples from X-ray diffraction experiments. The results provide previously unavailable details about the molecular conformation of this peptide, and demonstrate the value of this approach for the study of amyloid fibrils.

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Molecular Orientation in Polyester Films Using Polarized Laser Raman and Fourier Transform Infrared Spectroscopies and X-Ray Diffraction

Cited by 34 publications

References 38 publications

Determination of Orientation in Thermotropic Liquid Crystalline Polymer Films by Spectrographic Measurement of the Birefringence

Determination of Orientation in Thermotropic Liquid Crystalline Polymer Films by Spectrographic Measurement of the Birefringence

The Effect of Epoxidation on Strain‐Induced Crystallization of Epoxidized Natural Rubber

Determination of orientations of aromatic groups in self-assembled peptide fibrils by polarised Raman spectroscopy

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