The Preparation and Characterization of Small Mesopores in Siloxane-Based Materials That Use Cyclodextrins as Templates

• Published in: Advanced functional materials 2003-05, Vol.13 (5), p.382-386
• Main Authors: Yim, J.-H., Lyu, Y.-Y., Jeong, H.-D., Song, S.A., Hwang, I.-S., Hyeon-Lee, J., Mah, S.K., Chang, S., Park, J.-G., Hu, Y.F., Sun, J.N., Gidley, D.W.
• Format: Article
• Language: English
• Subjects: Cyclodextrins; Dielectric constant; Mesoporous films; Siloxanes
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.200304287

Porous thin films containing very small closed pores (∼ 20 Å) with a low dielectric constant (∼ 2.0) and excellent mechanical properties have been prepared using the mixture of cyclic silsesquioxane (CSSQ) and a new porogen, heptakis(2,3,6‐tri‐O‐methyl)‐β‐cyclodextrin (tCD). The pore sizes vary from 16.3 Å to 22.2 Å when the content of tCD in the coating mixture increases to 45 wt.‐% according to positronium annihilation lifetime spectroscopy (PALS) analysis. It has also been found that the pore percolation threshold (the onset of pore interconnectivity) occurs as the ∼ 50 % tCD porogen load. The dielectric constants (k = 2.4 ∼ 1.9) and refractive indices of these porous thin films decreased systematically as the amount of porogen loading increased in the coating mixture. The electrical properties and mechanical properties of such porous thin films were fairly good as interlayer dielectrics. Porous thin films, containing very small closed pores (∼ 20 Å—see Figure), with a low dielectric constant and excellent mechanical properties have been prepared using a mixture of cyclic silsesquioxane and cyclodextrin as a new porogen. The dielectric constants and refractive index of the films decrease systematically as the amount of porogen in the coating mixture is increased. The electrical and mechanical properties of such films are promising as interlayer dielectrics.