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Fractionation of Block Copolymers for Pore Size Control and Reduced Dispersity in Mesoporous Inorganic Thin Films

preprint
submitted on 08.05.2020 and posted on 11.05.2020 by Alberto Alvarez Fernandez, Barry Reid, Jugal Suthar, Swan Choy, Maximiliano Jesus Jara Fornerod, Niamh Mac Fhionnlaoich, Lixu Yang, Benjamin Schmidt-Hansberg, Stefan Guldin
Mesoporous inorganic thin films are promising materials architectures for a variety of applications, including sensing, catalysis, protective coatings, energy generation and storage. In many cases, precise control over a bicontinuous porous network on the 10-nm length scale is crucial for their operation. A particularly promising route for structure formation utilizes block copolymer (BCP) micelles in solution as sacrificial structure-directing agents for the co-assembly of inorganic precursors. This method offers pore size control via the molecular weight of the pore forming block and is compatible with broad materials library. On the other hand, the molecular weight dependence impedes continuous pore tuning and the intrinsic polymer dispersity presents challenges to the pore size homogeneity. To this end, we demonstrate how chromatographic fractionation of BCPs provides a powerful method to control the pore size and dispersity of the resulting mesoporous thin films. We apply a semi-preparative size exclusion chromatographic fractionation to a polydisperse poly(isobutylene)-block-poly(ethylene oxide) (PIB-b-PEO) BCP obtained from scaled-up synthesis. The isolation of BCP fractions with distinct molecular weight and narrowed dispersity allowed us to not only tune the characteristic pore size from 9.1±1.5 to 14.1±2.1 nm with the identical BCP source material, but also significantly reduce the pore size dispersity compared to the non-fractionated BCP. Our findings offer a route to obtain a library of monodisperse BCPs from a polydisperse feedstock and provide important insights on the direct relationship between macromolecular characteristics and the resulting structure-directed mesopores, in particular related to dispersity.

Funding

EPSRC (EP/R035105/1)

EPSRC (EP/M506448/1)

EPSRC (EP/L01646X)

MRC (MR/R000328/1)

EPSRC (EP/K038656/1)

History

Email Address of Submitting Author

s.guldin@ucl.ac.uk

Institution

University College London

Country

United Kingdom

ORCID For Submitting Author

0000-0002-4413-5527

Declaration of Conflict of Interest

No conflict of interest

Version Notes

Final version before initial peer review.

Exports