Journal
ACS NANO
Volume 8, Issue 12, Pages 11977-11986Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nn505037b
Keywords
directed self-assembly; nanoporous polymers; aligned membranes; magnetic alignment; LC mesophase; ionic conductivity
Categories
Funding
- NSF [CMMI-1246804, DMR-0847534, DMR-1119826]
- 3M Nontenured Faculty Award
- NSG Graduate Research Fellowship [DGE-1122492]
- NSF MRSEC program [DMR-1119826]
- DOE APRA-e program [D1-AR0000098]
- U.S. Bureau of Reclamation [R13AC80040]
- Division Of Materials Research
- Direct For Mathematical & Physical Scien [0847534] Funding Source: National Science Foundation
- Div Of Chem, Bioeng, Env, & Transp Sys
- Directorate For Engineering [1133484] Funding Source: National Science Foundation
- Div Of Civil, Mechanical, & Manufact Inn
- Directorate For Engineering [1246804] Funding Source: National Science Foundation
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There is long-standing interest in developing membranes possessing uniform pores with dimensions in the range of 1 nm and physical continuity in the macroscopic transport direction to meet the needs of challenging small molecule and ionic separations. Here we report facile, scalabe fabrication of polymer membranes with vertically (i.e., along the through-plane direction) aligned 1 nm pores by magnetic-field alignment and subsequent cross-linking of a liquid crystalline mesophase. We utilize a wedge-shaped amphiphilic species as the building block of a thermotropic columnar mesophase with 1 nm ionic nanochannels, and leverage the magnetic anisotropy of the amphiphile to control the alignment of these pores with a magnetic field. In situ X-ray scattering and subsequent optical microscopy reveal the formation of highly ordered nanostructured mesophases and cross-linked polymer films with orientational order parameters of ca. 0.95. High-resolution transmission electron microscopy (TEM) imaging provides direct visualization of long-range persistence of vertically aligned, hexagonally packed nanopores in unprecedented detail, demonstrating high-fidelity retention of structure and alignment after photo-cross-linking. Ionic conductivity measurements on the aligned membranes show a remarkable 85-fold enhancement of conductivity over nonaligned samples. These results provide a path to achieving the large area control of morphology and related enhancement of properties required for high-performance membranes and other applications.
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