Solid-State Proton NMR Characterization of Ethylene Oxide and Propylene Oxide Random and Block Copolymer Composites with Poly (methyl silsesquioxanes)

Solid-state proton NMR with fast magic-angle sample spinning has been used to study the structure and dynamics of block and random ethylene oxide/propylene oxide copolymers in the bulk and as 30 wt% composites with poly (methyl silsesquioxane). The composites are precursors to ultra-low dielectric constant materials used in integrated circuits. Proton NMR is used to identify the mobile propylene oxide component in the bulk copolymer samples. The polymer spectra are substantially different in the composite, demonstrating a fundamental difference in conformation. Dipolar filter NMR studies show that the propylene oxide is less mobile than the ethylene oxide in the block copolymer composites, suggesting that the propylene oxide is near the methyl silsesquioxane interface. The results from proton spin diffusion studies show that the polymer domain sizes in the composites are on the order of 5-6 nm, the size range of interest for the formation of ultra-low dielectric constant materials.