Block Copolymer Packing Limits and Interfacial Reconfigurability in the Assembly of Periodic Mesoporous Organosilicas |
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| Authors: | Andrew W. Wills David J. Michalak Peter Ercius Ethan R. Rosenberg Talita Perciano Daniela Ushizima Rory Runser Brett A. Helms |
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| Affiliation: | 1. The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA;2. Intel Corporation, Hillsboro, OR, USA;3. The National Center for Electron Microscopy, The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA;4. Computational Research Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA |
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| Abstract: | Here poly(N,N‐dimethylacrylamide)‐block‐poly(styrene) block copolymer micelles (BCPs) are advanced and applied to assemble periodic mesoporous organosilicas (PMOs) with noncylindrical pores. Using these BCP micelles, it is found that pore dimensions (11–23 nm), wall thicknesses (5–9 nm), and overall porosities (26%–78%) are independently programable, depending only on relative inputs for BCP and matrix former. Notably, the degree of order in all films improves as BCP loading approaches a packing limit of 63 vol%. Beyond this limit and regardless of pore dimensions, both porogen packing in the film and pore structure after thermal processing show significant deviations away from spherical close‐packed lattices. The surprising absence of film collapse in this regime allows here to quantify the evolution of pore structure through the thermally driven interfacial reconfigurability of BCP micelles in the hybrid films when porogen loading exceeds the packing limit by using both scattering techniques and scanning transmission electron microscopy tomography. Finally, the PMOs here give dielectric constants of 1.2 and 1.5 above and below the BCP packing limit, respectively—the lowest ever reported for this matrix material. |
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| Keywords: | block copolymers directed self‐assembly periodic mesoporous organosilicas thin films |
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