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

• Published in: Chemistry of materials Vol. 14; no. 1; pp. 249 - 255
• Main Authors: Mirau, Peter A, Yang, Shu
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.01.2002
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Physics
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/cm010543n

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) which are precursors to nanoporous ultralow dielectric constant films. The NMR results for the bulk diblock copolymer show that the propylene oxide block is relatively mobile and the proton line widths are effectively narrowed with 12 kHz magic-angle sample spinning, while most of the signals for the semicrystalline ethylene oxide block are too broad to be observed under these conditions. Both the ethylene oxide and propylene oxide signals are observed in the 30 wt % composite, demonstrating that the formation of crystalline domains in the ethylene oxide block is inhibited in the composite. Dipolar filter NMR experiments 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 5−7 nm, the size range of most interest for the formation of ultralow dielectric constant materials.