Crystal structures, polymers lattice parameters

Owing to the simphcity and versatility of surface-initiated ATRP, the above-mentioned AuNP work may be extended to other particles for their two- or three-dimensionally ordered assemblies with a wide controllabiUty of lattice parameters. In fact, a dispersion of monodisperse SiPs coated with high-density PMMA brushes showed an iridescent color, in organic solvents (e.g., toluene), suggesting the formation of a colloidal crystal [108]. To clarify this phenomenon, the direct observation of the concentrated dispersion of a rhodamine-labeled SiP coated with a high-density polymer brush was carried out by confocal laser scanning microscopy. As shown in Fig. 23, the experiment revealed that the hybrid particles formed a wide range of three-dimensional array with a periodic structure. This will open up a new route to the fabrication of colloidal crystals. 

The crystal in Fig. 5.34 illustrates the concept of isomorphism, the possibility that two different motifs fit into the same crystal. For polymers isomorphism of repeating units is most important. Isomorphism of complete chains is seldom possible. Polyfvinyl fluoride) that fits into a crystal of poly(vinylidene fluoride) provides a rare exception. The repeating-unit isomorphism can be separated into three types Type 1 occurs when both homopolymers have die same crystal structure, and a smooth change of the lattice parameters occurs on changing the concentration. An example of type 1 repeating-unit isomorphism is poly(vinylidene fluoride-co-vinyl fluoride). Type 2 is also called isodimorphism and occurs if the homopolymers have different crystal structures. A change in structure occurs at an intermediate concentration. Type 3 occurs if one homopolymer does not crystallize by itself, but participates in the crystal of the other. 

This polymer has been the archetypal one for applications of molecular mechanics to lattice packing. It is found for well-calibrated energy function parameter sets, i.e., force fields , that the crystal structure is rqjroduced well. Table 1 shows a comparison for lattice parameters between a calculation [6] and experiment... 

Both crystal structures are monoclinic with two monomers or monomer units of different orientation per unit cell (Fig. 9.3 sketches only one of these two.). The chemical bond between two carbons of nearest neighbour diacetylenes (1,4-addition) results in the linear polymer chain and the small change in the lattice parameter along the b-axis prevents the destruction of the macroscopic single crystal during the topochemical reaction. Several surfaces of diacetylene crystals have been studied by atomic force microscopy (AFM) in order to investigate both, the single crystal surface structure and solid state reactions at the surface [129, 131]. 

The crystal structure ofpolychlorotrifluoroethylene has been determined by x-ray diffraction and accepted to be pseudohexagonal with lattice parameters of a = 0.644 nm and c = 4.15 nm.[ k31] xhe polymer chain is... 

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