Plasticity crystallization and

Plastic crystals and crystals with orientational disorder still fulfill the three-dimensional translational symmetry, provided a mean partial occupation is assumed for the atomic positions of the molecules whose orientations differ from unit cell to unit cell ( split positions ). 

Note 2 The term is used to describe orientationally disordered crystals, crystals with molecules in random conformations (i.e., conformationally disordered crystals), plastic crystals and liquid crystals. 

Plastic crystals and crystals with orientational disorder still fulfill the three-dimensional... 

Figure 6. Phases for systems which give I, crystal, anisotropic liquid, and isotropic liquid II, crystal and isotropic liquid III, crystal, cubic plastic crystal, and isotropic liquid (8)...

Long-Term Permeability in Polyethylene-Nylon Laminar Walled Containers. Polyolefin containers often are subject to loss of properties with aging. These result from plasticization, crystallization, and stress cracking. Figure 8 shows the permeability properties of 66/6 copolyamide based "laminar" blends. The permeability performance was found to be unchanged during over 5 years of storage in the two separate samples shown here. 

The differences between the three mesophases, liquid crystal, plastic crystal and condis crystal could be clarified and, although difficult to classify, intermediate cases remain. If the molecule permits dynamic conformational disorder in the liquid phase, the same is usually also possible in a similar temperature range in the liquid-crystalline and plastic-crystalline phases. 

Plastic crystals and liquid crystals Hereafter q and 5 will be understood to refer to those values that satisfy (2.1.2) and (2.1.3). For low zW/k T, = 0 is the only solution that... 

Plastic crystals are more closely related to the classical crystals. They have full positional order as shown in the sketch in Fig, 2.105. The plastic crystal consist, however, of molecules (their mesogens) that are almost spherical and can start to rotate within the crystal at a given transition temperature. Figure 2.107 contains a list of typical properties of plastic crystals and allows a comparison to liquid crystals. The plastic crystalline state was first recognized in the 1930 s. Most plastic crystals... 

Figure 5.119 extends the list of almost spherical motifs to much larger, organic molecules with a molecular stmcture which is still close to spherical. Again, these molecules are plastic crystals and have gained orientational mobihty before ultimate... 

Liquid crystals, plastic crystals and condis crystals... 

To begin with, and contrary to a still widely held belief, the words liquid-crystalline and mesomorphic are not synonymous. The term mesomorphic phases was introduced by Friedel in 1922 [1] it is now often abbreviated to meso-phases. He defined them as phases with microscopic structures between solids and ordinary isotropic liquids. Not much happened in this area until 1955 when Kast [2] tried to characterize such phases in terms of lateral, longitudinal, and steric disorder. The next step occurred in 1984 when Wunderlich and Grebowicz [3] defined condis crystals for the first time. Following them [3,4] we now distinguish three kinds of mesophases liquid crystals, plastic crystals, and condis crystals. 

Hooper JB, Borodin O (2010) Molecular dynamics simulations of N, N, N, N-tetramethylammonium dicyanamide plastic crystal and liquid using a polarizable force field. Phys Chem Chem Phys 12 4635... 

In contrast to liquid crystals that always possess oiientatioiial order and sometimes have positional order, there is another phase of matter that possesses positional order but no orientational order. Materials in this phase are called plastic crystals and are said to exhibit rotator phases, because the molecules freely rotate along one or more of their molecular axes, even though their centres of mass are fixed in a lattice. 

Halide salts of quaternary ammonium and phosphonium cations, and those derived from heterocyclic bases (both aromatic and alicyclic), have long been known (Table 11.14). Most are relatively high melting (and would not be considered ionic liquids), though the structural characteristics of quaternary ammonium halides have been studied by those with interests in plastic crystals and so-called rotator phases [7]. Many deconpose at or near their melting temperatures, a characteristic that would limit interest in them as reaction media [667]. Indeed, it is probably as a result of the view, widely held in the past [668], that such materials may be intrinsically unstable that the onset of the recent massive interest in ionic liquids was delayed. 

Rana, U.A., Vijayaraghavan, R., Doherty, C.M., Chandra, A., Efthimiadis, J., Hill, A.J., MacFarlane, D.R. and Forsyth, M., Role of defects in the high ionic conductivity of choline triflate plastic crystal and its acid-containing conpositions, J. Phys. Chem. C117 (11), 5532-5543 (2013). 

Conference on Plastic Crystals and Rotation in the Solid State, J. Phys. and Chem. Solids, 1961,18, 1-92. 

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