Topographic matching

When sPP crystallizes epitaxially on 2-quinoxalinol (2-Quin) at a low temperature, the metastable Form II is obtained, as evidenced by its different, specific diffraction pattern [58]. Contrary to the monoclinic phase of PE, formation of this metastable phase is not linked with a better dimensional match. Rather, it stems from a much superior topographic match between the polymer and the substrate. The crux of the argument can be summarized in a three-part figure (Fig. 8.10). When seen from the side, the contact face of 2-Quin displays relatively long-range ridges with a periodicity that matches the c-axis repeat distance of sPP. The profiles... 

Figure 8.10 Topographic matching between 2-quinoxahnol (left) and syndiotactic polypropylene in its Form II (middle, isochiral hehces) and its Form I (right, antichiral helices). Correspondence of the 2-Quin and Form II profiles explains the formation of the latter, metastable structure. Reproduced from Reference [58] with permission of the AmericanChemi-cal Society.

The rules that govern polymer epitaxy have been deduced mainly from the analysis of observed epitaxies. The dimensional match at the unit-cell scale merely implies that the local favorable interaction are repeated on a two-dimensional (or at least on a one-dimensional) array in the contact plane. The topographic matching refers to the unit-cell scale interactions. In some instances (illustrated earlier with, e.g., the formation of the sPP Form II on 2-quinoxaUnol) the topographic requirements are obvious and indeed intuitively sound. 

In a grand theft case a critical aspect of the case involved the matching of lacquered wood which was an integral part of the stolen merchandise with wood found at the suspect s work area. The composition comparison of the lacquer is shown in Figure 8. The topographical comparison of the wood (coniferous) is shown in Figure 9. The positive comparison obtained in both independent analyses was confirmed by IR techniques. 

Chlorine is well studied for its biological, and especially for, its electrolyte significance. It is essential for almost every organism and likely has a catalytic function. It is moderately toxic to mammals when injected intravenously, otherwise it is relatively harmless. It has received intense attention because of its well-known essentiality, but its topographical distribution in the human brain is less known. Significantly decreased chlorine-adenosine-triphosphatase (Cl-ATPase) activity has been reported 1998 in AD brains, compared to age-matched controls (Hattori et ai, 1998). 

Just as topographic features can be used to control dewetting in single component polymer films, such templates also can be used to control polymer blend and block copolymer phase segregation. A difficulty with BCPs, however, is generating a template with sufficiently small feature sizes to match the natural phase separation... 

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