Crystal domain

The substituted five-ring OPVs have been processed into poly crystal line thin films by vacuum deposition onto a substrate from the vapor phase. Optical absorption and photolumincscence of the films are significantly different from dilute solution spectra, which indicates that intermolecular interactions play an important role in the solid-state spectra. The molecular orientation and crystal domain size can be increased by thermal annealing of the films. This control of the microstruc-ture is essential for the use of such films in photonic devices. 

However, another obstacle to high bulk conductivity of such a polymer exists. In view of the hnite length and vast number of constitutive polymer chains, bulk conduction requires electrons to jump between chains (or polarons to transfer between chains in the opposite direction). It is obvious, then, that local order, crystallinity, and good contact between the different crystal domains in the polymer are further prerequisites for conduction. 

Sample Specific surface area (mVg) Pore volume (ml/g) Pore size (nm) Crystal domain size (nm) Ag weight percent (%)... 

Powder X-ray diffraction has verified that the isomerization occurs via a crys-tal-to-crystal reaction process, and that the diffraction profiles of the crystals after photoirradiation consist of overlapped patterns of diffraction due to the crystals of 10 and 11. This indicates that the crystal domains of each isomer exist simultaneously in the crystals accompanied by crystal phase separation during the photoisomerization. Single crystal structure analysis has disclosed that the crystals of 11 as the photoproduct have a symmetry different from that of the starting crystals of 10 (Fig. 14). 

P. Moldenaers, G. G. Fuller and J. Mewis, Mechanical and optical rheometry of polymer liquid-crystal domain structure, Macromolecules, 22,960 (1989). 

The depletion in FeO may be understood in at least two ways. First, the crystalline grains may be equilibrium condensates from a hot solar nebular composition gas with iron sequestered to metals or sulfides (see e.g. Chapter 4). In this case the condensed grains either had to condense slowly to form crystal domains, or had been reheated and thermally annealed at a later epoch. The second, alternative explanation is that ferromagnesian amorphous silicate grains were thermally annealed in a reducing environment, e.g. in the presence of carbon. Heating such precursors leads to the formation of metallic spheroids embedded between the forsterite crystals, as the initial FeO component is reduced (see e.g. Fig. 8.3 and Connolly et al. 1994 Jones Danielson 1997 Leroux et al. 2003 Davoisne et al. 2006). Because carbon is ubiquitously present in primitive Solar System materials, this pathway offers a natural explanation to the observed FeO-poor silicate crystals. It is yet to be determined whether low-temperature crystallization processes, discussed in Section 8.1.1, would also lead to FeO depletion. 

---