Structure frustrated

Figure 4.6 (a) Schematic view of the two degenerate helical arrangements of the spins of a ID frustrated structure with antiferromagnetic next-nearest-neighbour (NNN) interactions. The angle is the one formed between the projections of two adjacent spins, drawn with different colours to... 

Mesophase with a three-dimensional spatial distribution of helical director axes leading to frustrated structures with defects arranged on a lattice with cubic symmetry and lattice constants of the order of the wavelength of visible light. 

The crystal polymorphism of the chiral but racemic P5MH1 is, to some extent, very reminiscent of that of isotactic polypropylene. It exists in two crystal modifications. One crystal modification is stable at high temperature, and was observed early on by Corradini et al [39]. Its structure has been redefined as a chiral, frustrated one based on a trigonal cell with three threefold helices per cell. We have also discovered a second crystal modification produced from solution. It has an orthorhombic unit cell that contains four chains in - again - three-fold helical conformation, for which one must assume coexistence of two right- and two left-handed helices. Contrary to the a and ft phases of iPP, the frustrated structure of poly( 5-methyl-hexene-1) is the more stable one [40]. 

From a nanoscale point of view, /3-PP crystallizes in a hexagonal form with a = b = 11.01 A and c = 6.49 A (the space group is probably P3i) [86,96-98]. It belongs to a class of polymers which displays a frustrated structure, referring to the fact that the helices in the unit cells have different azimuthal settings [37,99-101]. The relative amounts of a- and /3-forms in a sample are controlled by intrinsic molecular parameters and extrinsic factors. They will be discussed in detail in Sect. 3.2. 

Puiggali J., Ikada Y., Tsuji H., Cartier L., Okihara T., Lotz B., The frustrated structure of polyfL-lactide), Polymer, 41, 2000, 8921-8930. 

Triangular polymer single crystals stereocomplexes, twins, and frustrated structures. Macromolecules,... 

The chemical structures of PLA, including the chain structure, configuration, tacticity, conformation, and the frustrated structure, are important parameters that govern... 

The chemical structures of PLA, including chemical composition, interlocked structure, isomers, syndiotacticity, conformation, amorphous structure, semicrystal structure, frustrated structure, molecular weight, and so on, were reviewed in this chapter. The chemical structures play an... 

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