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Crystalline Polymers
Published in Timothy P. Lodge, Paul C. Hiemenz, Polymer Chemistry, 2020
Timothy P. Lodge, Paul C. Hiemenz
In this section we shall examine the smallest level of structure displayed by polymer crystals: the unit cell. Unit cells typically have dimensions between 2 and 20 Å, which lie in the same range as atomic and small-molecule crystals. Accordingly, the same experimental technique is employed to determine the spacings and the symmetries of the unit cell, namely X-ray diffraction (XRD), or, as it is more commonly known in polymer science, wide-angle X-ray scattering (WAXS). We will not describe WAXS in detail, but the basic process can be understood through comparison with the determination of molecular structure and size by light scattering, which was covered in Chapter 8. Similarly, we will only review the basics of crystallography; more details are available in a number of monographs and texts.
Characterization Techniques
Published in Chandan Das, Sujoy Bose, Advanced Ceramic Membranes and Applications, 2017
SAXS (small-angle x-ray scattering) is an analytical method to determine the information related to averaged particle sizes, shapes, geometry and bulk morphology at a molecular level for a wide variety of samples, such as metals, ceramics, polymers, biological molecules, etc., in the forms of solids, liquids, liquid dispersions, films, gels, ground powders, and molecules in gaseous phase. When such a sample is exposed by x-rays, the sample scatters the radiation differently depending on its constituents to create a contrast that helps to draw conclusions about the particle structure and its arrangement in the system. Apart from this basic information, much other information can be obtained from SAXS—namely, characteristic distances of partially ordered materials, radius of gyration (Rg) to calculate particle dimensions, molecular weight of particles, structures, polydispersity analysis, molecular interactions, their orientations, degree of crystallinity, etc.
Structures of Polymer/Nanofiller Interfaces
Published in Toshikatsu Tanaka, Takahiro Imai, Advanced Nanodielectrics, 2017
Toshikatsu Tanaka, Muneaki Kurimoto
Small-angle X-ray scattering (SAXS) is a technique of measuring X-rays scattered at a small angle of < 5° and is used to analyze the structure of a specimen 1–100 nm in size. Figure 7.11a shows the SAXS profiles of a nanocomposite consisting of colloidal silica with a particle size of 110 nm and resin. The profiles were obtained using the high-brilliance synchrotron radiation generated at SPring-8 [10]. The peak in the range of q = 0.02–0.06 nm−1 shifts rightward with increasing filling amount of nanofiller. Peaks of q ≥ 0.08 nm−1 agree among different filling amounts, indicating that there is no aggregation of nanofiller particles. Figure 7.11b shows the distance between nanofiller particles calculated on the basis of the peak values. With increasing filling amount of nanofiller, the number density of nanofiller particles increases and the distance between nanofiller particles decreases. The results in Fig. 7.11b were observed to be similar to those obtained by electron microscopy observation.
Optimization of sample thickness for small angle X-ray scattering (SAXS)
Published in Instrumentation Science & Technology, 2023
Haijuan Wu, Rongchao Chen, Zhihong Li
Small-angle X-ray scattering (SAXS) is a physical method that may derive the geometric structure information of materials at nanometer scale such as fractal dimensions, scatterer volume percentage, specific surface area, and scatterer size and distribution.[1,2] SAXS is able to measure almost any sample with fluctuations in electron density, such as polymers, surfactants, colloids, protein solutions, porous media, nanoparticles, and nanocomposites.[3–9] In SAXS, the signal is caused by scatterers with a certain electron density (such as particles in space and pores in continuum) immersed in a medium with another electron density. The scattering pattern reflects the spatial relationship of the scatterers and is an average over time. The scattering intensity versus angle is related to the shape, size, and spatial distribution of the scatterers in the system and is proportional to the difference of electron density between the scatterer and the medium.[1]
The effect of molecular structure on mesophase behaviour of non-symmetric liquid crystal dimers containing mandelic acid and fluorine group
Published in Liquid Crystals, 2020
Xin-Shi Chen, Zhi-Xin Xu, Zhu Chen, Lan-Rui Bai, Xiang-Yu Zang, Yu-Nong Li, Dan-Shu Yao, Ying-Gang Jia, Mei Tian
Differential Scanning Calorimetry (DSC) measurements are carried out with a NETZSCH instruments DSC 204 (Netzsch, Wittelbacherstrasse, Germany) at a scanning rate of 20°C min−1 under a flow of dry nitrogen. Nuclear magnetic resonance hydrogen spectrometer (1H NMR) (600 MHz) is measured by Bruker BioSpin AG (Bruker, Fällanden, Switzerland), Fourier Transform Infrared Spectroscopy (FTIR) is measured by PerkinElmer instruments Spectrum One Spectrometer (PerkinElmer, Foster City, CA, USA), respectively. X-ray diffraction (XRD) measurements are performed with nickel-filtered Cu Kα (λ = 1.54 Å) radiation with a D8 ADVANCE XRD (Bruker, Karlsruhe, Germany). Thermogravimetric analysis (TGA) measurement is carried out with a NETZSCH TGA 209C thermogravimetric analyser. The X-ray measurements include wide-angle XRD experiments and small-angle X-ray scattering measurements. Measurement of optical rotation (α) is carried out with a Anton Paar instrument Model MCP-100 Polarimeter at room temperatures using LED light source (λ = 589 nm). The polarised optical microscopy (POM) study is performed using a Leica DMRX (Leica, Wetzlar, Germany) equipped with a Linkam THMSE600 (Linkam, Surrey, England) heating stage.
Fluorinated chiral nematic liquid crystal dimers based on (S)-1-phenylethane-1,2-diol
Published in Liquid Crystals, 2020
Xiang-Yu Zang, Li Gao, Rui Zhang, Liang Dong, Xin-Shi Chen, Yu-Nong Li, Dan-Shu Yao, Jian-She Hu, Ying-Gang Jia, Feng-Hong Li, Mei Tian
Nuclear magnetic resonance hydrogen spectrometer (1H NMR) (600 MHz) and Fourier transform infrared spectroscopy (FTIR) are measured by Bruker BioSpin AG (Bruker, Fällanden, Switzerland) and PerkinElmer instruments Spectrum One Spectrometer (PerkinElmer, Foster City, CA, USA), respectively. The elemental analyses are carried out on an Elementar Vario EL III (Elementar, Hanau, Germany). Differential scanning calorimetry (DSC) measurements are carried out with a TA instruments DSC 25 TA (New Castle, DE, American) at a scanning rate of 20°C min−1 under a flow of dry nitrogen. Thermogravimetric analysis (TGA) measurements are carried out with a NETZSCH TGA 209C thermogravimetric analyser. X-ray diffraction (XRD) measurements are performed with nickel-filtered Cu Kα (λ = 1.54 Å) radiation with a D8 ADVANCE XRD (Bruker, Karlsruhe, Germany). The X-ray measurements include wide-angle XRD experiments and small-angle X-ray scattering measurements. Measurement of optical rotation (α) is carried out with a PerkinElmer instrument Model 341 Polarimeter at room temperatures using sodium light source (λ = 589 nm). The polarised optical microscopy (POM) study is performed using a Leica DMRX (Leica, Wetzlar, Germany) equipped with a Linkam THMSE-600 (Linkam, Surrey, England) heating stage.