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Application of AFM for Analyzing the Microstructure of Ferroelectric Polymer as an Energy Material
Published in Cai Shen, Atomic Force Microscopy for Energy Research, 2022
To understand the application of the fluoropolymer as an energy material, it is necessary to understand their microstructural characteristics. PVDF and P(VDF-TrFE) have similar crystallographic structure, and both have four polymorphs related to different conformations of the molecules as listed in Table 9.1. The lattice structure of different polymorphs is schematically illustrated in Figure 9.1. Note that the lattice parameters are different for the copolymer with different VDF/TrFE ratios. The phase transition between the polymorphs can be induced by stress or thermal treatment. In order to display ferroelectric behaviors, the chains of the ferroelectric polymers must be able to crystallize in a manner in which the F-C-H molecular dipoles do not cancel out. Consequently, only the polar phases are ferroelectrics.
Introduction to Organic Photo Actuator Materials and Devices
Published in Sam-Shajing Sun, Larry R. Dalton, Introduction to Organic Electronic and Optoelectronic Materials and Devices, 2016
Lingyan Zhu, Taehyung Kim, Rabih O. Al-Kaysi, Christopher J. Bardeen
Polymorphism is the ability of a solid material to exist in more than one form or crystal structure. Polymorphism can potentially be found in any crystalline materials and different polymorphs can exhibit very different solid-state reactivities. One example is the dianthracene molecule 9-anthracenecarboxylic acid, methylene ester (9AC-ME) [77]. 9AC-ME can crystallize into two different polymorphs, which are shown in parts (a) and (b) of Figure 31.23. Under high-temperature solvent annealing conditions, the crystal polymorph grows as a π-stacked type where the stacked anthracenes alternate from molecule to molecule. This crystal structure is shown in Figure 31.23a and is of a type where the anthracenes of neighboring molecules have the correct spacing and alignment to undergo a [4 + 4] photocycloaddition reaction. This leads to the formation of a crystalline polymer. The polymerization reaction takes place only for this crystal polymorph of 9AC-ME. The more stable crystal polymorph formed at room temperature, shown in Figure 31.23b, does not have the anthracene groups correctly oriented to undergo the [4 + 4] photodimerization, and this type of crystal is completely inert under the same irradiation conditions.
Drug Solubility and Solubilization
Published in Sandeep Nema, John D. Ludwig, Parenteral Medications, 2019
Ching-Chiang Su, Lan Xiao, Michael J. Hageman
Polymorphs exist when two crystals have the same chemical composition but different unit cell dimensions and crystal packing. Compounds that crystallize as polymorphs generally have different physical and chemical properties, including different melting points, X-ray diffraction patterns, and solubilities. Generally, the most stable polymorph has the highest melting point and lowest solubility; other polymorphs are metastable and convert. A consideration of the data in the literature indicates that improvements in the solubility of metastable crystal forms can be expected to be as high as twofold (25).
Drying induced polymorphic transformation of pharmaceutical ingredients: a critical review of recent progresses and challenges
Published in Drying Technology, 2022
Jayanta Chakraborty, Midhuna Subash, Bhaskar N. Thorat
Raman spectroscopy is another method for detection and quantification of various polymorphs. It is an important technique used to identify the transformation between distinct solid-state forms. Same molecule will show different polymorphs and each having distinct crystalline forms. Each crystalline form is having unique Raman spectrum. Different polymorph will show difference in peak position as well as intensities in the Raman spectra. Another difference seen in the Raman spectra of distinct polymorphic forms is band splitting and shifting. An example of typical Raman spectra of pure polymorphic forms and their mixture is shown in Figure 12. Raman spectroscopy has several advantages compared to others: Raman does not require any special sample preparation and noninvasive. Raman spectroscopy has also been used for in-line monitoring of polymorphs: one particular example is the case of fulfenamic acid.[70]
Binary mixtures of bent-core molecules forming distinct types of B4 phase nano- and microfilament morphologies
Published in Liquid Crystals, 2021
Jiao Liu, Sasan Shadpour, Ahlam Nemati, Marianne E. Prévôt, Elda Hegmann, Chenhui Zhu, Torsten Hegmann
Polymorphism, the ability of certain compounds that are chemically identical to exist in more than one form that differs in physical properties such as density, crystal structure, spectral signatures, melting point, or solubility [1], is of major concern in drug and materials development [2]. Similarly, polymorphism of chemical elements, termed allotropy, has equally impactful consequences in many branches of chemistry and materials science. For example, in the case of carbon, its allotropy encompasses distinct polymorphic shapes such as fullerenes, nanotubes, carbon nanofoams, and graphene sheets in addition to graphite, diamond, lonsdaleite, as well as amorphous carbon among others [3]. Here, differences in structure determine shape and greatly impact macroscopic properties. A prime example of polymorphism in soft matter is the liquid crystalline state, where multiple forms (phases) can be observed for a given material depending on temperature or the concentration of an amphiphilic species such as surfactants, anisometric clays and nanomaterials, aggregates of molecules, etc., in a solvent, and further affected by temperature [4–8]. The self-assembly and degree of ordering (in one, two or three dimensions) in these phases can differ greatly, and a subset of these phases is characterised by the self-organisation of molecules and ensuing assemblies into distinct three-dimensional (3D) crystal lattices as in the case of blue phases [9–12] or by the self-organisation of the resulting quasi-crystalline building blocks. Among these phases, the so-called B4 phase formed by bent-core liquid crystals (BCLCs) stands out as a particularly intriguing example of morphological variety [13]. The B4 phase, while limited to certain subsets of bent-core molecules with specific molecular building blocks, results from the hierarchical self-assembly of twisted layer (tape) or helical ribbon morphologies at the nano- to mesoscale [14].
Factors affecting the formation of alpha and beta polymorphs in glutaric acid aerosols
Published in Aerosol Science and Technology, 2019
Phoebe C. Belser, Hemanta R. Timsina, Timothy M. Raymond, Dabrina D. Dutcher
In this experiment, samples were collected in order to analyze the polymorphs present under different conditions using Powder X-Ray Diffraction (PXRD). The PXRD was used because it has the capacity to distinguish between polymorphs of aerosols and to compare samples to databases of preexisting diffractograms to identify the crystals present. PXRD is also able to distinguish clearly between amorphous phases, crystalline phases, or combinations of the two (Brundle et al. 1992).