Crystallography, bonding and energy of DCH crystalline polymer/nanocrystalline metal interfaces.

摘要

Theoretical and experimental results concerning the interaction between a crystalline polymer and a variety of nanocrystalline metal crystals are presented and analyzed. Attention is focussed on aspects of the interaction that concern interfacial bonding, its correlation with the cohesive energies of various metals and the energy of the interfaces.;Experimental contributions include qualitative estimates of the magnitude of interfacial energies for the crystalline polymer/metal and amorphous carbon/metal interfaces and a direct measurement of the interfacial energies for the Au and Ag nanocrystals deposited on the amorphous carbon substrate. The theoretical part of the study includes molecular orbital type calculations for the polymer cluster believed to be active with the metals in interfacial bonding.;The sequence of interfacial energy values for the polymer/metal and amorphous carbon/metal systems was also determined. The interfacial energies for both the poly-DCH and amorphous carbon substrates decreases in the order Ag, Au, Ni, and Cr, as expected from cohesive energy, melting point and surface energy data.;It is well known that metal/metal, ceramic/metal and polymer/alkali-halide interfaces exhibit orientation relationships, either as a coincident site two-dimensional lattice or due to linear close-packed directional matching. We examined the crystalline polymer/metal interface for the presence of orientation relationships using selected area diffraction in the transmission electron microscope (TEM) and optical diffractometry of high-resolution TEM images. No orientation relationships were found for any of the polymer/metal combinations spanning a large range of metal reactivities. Lack of atomic matching or some as yet unknown surface condition on the polymer may be responsible for this effect.;Electronic structure calculations for a polymer constituent part, the carbazole group, were performed in order to determine minima in the electron charge density distribution, which are potential attachment sites for deposited metal atoms. Calculations of the charge density for carbazole/gold and carbazole/nickel clusters were performed as representative structures of the polymer/metal interface. These calculations were found to correlate well with reactivity data and experimental results for the two metals.