Oriented nucleation of inorganic salts on polymeric long chain acid monolayers

Directed crystallization of calcite and CdS was studied on polymerized 10,12 pentacosadiynoic acid (p-PDA) template. Precise lattice match between calcite a axis and, the carboxylates periodicity along the linear polymer backbone, and stereochemical fit between the titled monolayer and inclined carbonate at the (0 1 2) of calcite, induce total control of calcite nucleation. Polymer crystalline domains can be several hundreds of micrometers in dimension. Consequently, the templated calcite crystals are all coaligned within this range. p-PDA film with CdS nucleated on it, produces a selected area electron diffraction pattern which is a superimposition of 4 different projection of CdS FCC structure. All the projections have a common (2 2 0) diffraction spot, suggesting alignment along this direction. This suggests that crystallites can in fact be in any orientation with only one crystal axis aligned with the substrate. This represents a unique example of template crystallization where limited control is manifested. The p-PDA film is particularly suitable for template nucleation studies due to its rigidity and large domains. This results in well-defined crystal orientation over the extent of the substrate domains. (C) 1999 Published by Elsevier Science B.V. All rights reserved.