In an attempt to develop a low-k interlayer dielectric, adamantane-diphenyldiethynyl moiety containing oligomer is prepared. Oligomerization of 1,3,5,7-tetra-kis[3/4-ethynylphenyl]adamantane (4) is accomplished by a Glaser-Hay oxidative coupling with 1,3,5-triethynylbenzene and phenylacetylene end-capping agent. The CHCl3 soluble oligomer is then thermally treated by step-curing at 200, 300, 380, and 450 degrees C for 30 min at each temperature under nitrogen flow to render a shiny void-free black polymer, TGA analysis indicates that the polymer is stable under nitrogen up to 500 degrees C with a marginal decomposition up to 800 degrees C. Solid-state C-13 NMR, Raman scattering, and FTIR are used to characterize the structure of the polymer. The polymer consists of amorphous carbon networks with the adamantane moieties and nanosized graphitic regions (clusters), which are generated from the thermal crosslinking of the diphenyldiethynyl units. It shows a remarkably low linear coefficient of thermal expansion (similar to 25 ppm/degrees C), presumably due to the presence of the disordered graphitic structure. Its high density (similar to 1.21 ppm/degrees C), refractive index (similar to 1.80 at 632 nm), and Young's modulus (similar to 17.0GPa)are also consistent with the interpretation. This study reveals important details about the effect of microscopic structure on the macroscopic properties of the highly crosslinked polymer. (c) 2006 Wiley Periodicals, Inc.