True Single-Crystal Character

Among all CPs, there is only one class that appears to display true single-crystal character. This is the poly(diacetylenes) (P(DiAc)s), discussed separately in a subsequent chapter in this book. Large (up to 1 cc) near-single crystals can be grown, with estimated coherence lengths of up to 1,000 monomer units (ca. 1 /tm in length) [325]. 

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Anthracene is the smallest linearly-fused aromatic species considered to exhibit true acene character (Fig. 14.2) and has been the smallest acene typically studied for electronic materials applications [12]. Single-crystal anthracene does exhibit relatively high intrinsic hole mobility, with values as high as 3 cm2 XT1 s 1 measured by the time-of-flight technique and as high as 0.02 cm2 V-1 s 1 measured from a FET constructed on a single crystal [13], Films of functionalized anthracene derivatives have also yielded FETs with reasonable hole mobilities (see... 

The unusual feature, plus several other structural peculiarities, led to the collection of a new set of single crystal data.62 Numerous faint reflections showed that the cell is not centered and that the true space group is Pcca. The new structure confirms the expected ionic character of this salt and contains no surprising features. 

Before discussing the use of such character tables, we will illustrate how the appropriate one is obtained for a given polymer structure. As an example, let us take a single planar zig-zag (infinitely long) polyethylene chain. The complete analysis requires us to use the true crystal structure, which contains two chains per unit cell [Bunn (26)], but it has been... 

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