Nanoporous ultralow dielectric constant organosilicates templated by triblock Copolymers

Triblock polymers,poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (PEO-B-PPO-b-PEO), are used as molecular templates in poly(methyl silsesquioxane) (MSQ) matrices to fabricate nanoporous organosilicates. It is found by solid-state NMR that initially homogeneous blends of the triblock copolymer and the MSQ precursor microphase separate during a curing step when the MSQ becomes increasingly hydrophobic. The polymer domain size in the MSQ composites, 3-10 nm, depends on the polymer architecture and loading percentage. The block polymer templates are then decomposed when heated to >= 400 degrees C to generate pores in the MSQ matrices. Small angle neutron scattering (SANS) and positronium annihilation lifetime spectroscopy (PALS) reveal that pores are extremely small pores (2-5 nm). These nanoporous materials can attain ultra low-dielectric constants (k = 1.5) at to% porosity with superior electrical and mechanical properties.