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Triblock polymers trapped in the fluctuating disordered state were investigated as precursors to nanoporous ultrafiltration membranes. The triblock explored is poly(lactide)-b-poly(oligoethylene glycol methyl ether methacrylate)-b-poly(styrene-s-methyl methacrylate) (PLA-POEGMA-PSMMA), where PLA is the etchable pore-forming block, POEGMA is the hydrophilic pore-lining block, and PSMMA is the matrix block. Bicontinuous microphase-separated domains were obtained thermally by heating the polymer melt above the order-disorder transition temperature (TODT) followed by quenching below the glass transition temperature (Tg), or isothermally by spin coating the block polymer solution at ambient conditions. POEGMA is miscible with PLA but not PSMMA and should therefore colocalize with PLA and be exposed on pore surfaces after selective PLA etching. The triblock polymers have similar ODT behavior as diblock polymers, and the presence of an accessible TODT in the melt depends strongly on the segregation strength χPLA-PSMMAN. Composite membranes with block polymer selective layers were prepared by spin coating the triblock polymer onto water-filled nylon membranes, where rapid solvent evaporation enabled the block polymer to be vitrified in the disordered state. The resulting membranes have uniform surface pores, high permeabilities, and small improvements in surface hydrophilicity, and the approach may be applied to target other surface functionalities.
Bibliographical noteFunding Information:
Portions of this work were performed at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) located at the Sector 5 of the Advanced Photon Source (APS). DND-CAT is supported by E.I. DuPont de Nemours & Co., the Dow Chemical Company, and Northwestern University. Use of the APS, an Office of Science User Facility operated for the U.S. DOE Office of Science by Argonne National Laboratory, was supported by the U.S. DOE under contract no. DE-AC02-06CH11357. The authors are extremely grateful to Steven Weigand for help with collecting SAXS data. SEM and microscopic contact angle data were collected at the UMN Characterization Facility, which receives partial support from NSF through the MRSEC program. The authors would like to thank Nicholas Hampu and Jay Werber for reviewing the manuscript.
Funding for this work was provided by the National Science Foundation (DMR-2003454) and the University of Minnesota President’s Postdoctoral Fellowship Program.
© 2022 American Chemical Society.
- fluctuating disordered state
- hydrophilic ultrafiltration membranes
- selective etching
- solution casting
- triblock polymer
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