Size Control and Fractionation of Ionic Liquid Filled Polymersomes with Glassy and Rubbery Bilayer Membranes

Soonyong So, Timothy P. Lodge

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

We demonstrate control over the size of ionic liquid (IL) filled polymeric vesicles (polymersomes) by three distinct methods: mechanical extrusion, cosolvent-based processing in an IL, and fractionation of polymersomes in a biphasic system of IL and water. For the representative ionic liquid (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([EMIM][TFSI])), the size and dispersity of polymersomes formed from 1,2-polybutadiene-b-poly(ethylene oxide) (PB-PEO) and polystyrene-b-poly(ethylene oxide) (PS-PEO) diblock copolymers were shown to be sensitive to assembly conditions. During mechanical extrusion through a polycarbonate membrane, the relatively larger polymersomes were broken up and reorganized into vesicles with mean size comparable to the membrane pore (100 nm radius); the distribution width also decreased significantly after only a few passes. Other routes were studied using the solvent-switch or cosolvent (CS) method, whereby the initial content of the cosolvent and the PEO block length of PS-PEO were systemically changed. The nonvolatility of the ionic liquid directly led to the desired concentration of polymersomes in the ionic liquid using a single step, without the dialysis conventionally used in aqueous systems, and the mean vesicle size depended on the amount of cosolvent employed. Finally, selective phase transfer of PS-PEO polymersomes based on size was used to extract larger polymersomes from the IL to the aqueous phase via interfacial tension controlled phase transfer. The interfacial tension between the PS membrane and the aqueous phase was varied with the concentration of sodium chloride (NaCl) in the aqueous phase; then the larger polymersomes were selectively separated to the aqueous phase due to differences in shielding of the hydrophobic core (PS) coverage by the hydrophilic corona brush (PEO). This novel fractionation is a simple separation process without any special apparatus and can help to prepare monodisperse polymersomes and also separate unwanted morphologies (in this case, worm-like micelles).

Original languageEnglish (US)
Pages (from-to)4959-4968
Number of pages10
JournalLangmuir
Volume32
Issue number19
DOIs
StatePublished - May 17 2016

Bibliographical note

Funding Information:
This work was supported by the National Science Foundation through Award DMR-1206459. Cryo-TEM measurements were carried out in the Characterization Facility, University of Minnesota, which has received capital equipment funding from the NSF through the UMN MRSEC program, under Award DMR-1420013. We acknowledge Dr. Robert Hickey and Prof. Yeshayahu Talmon for helpful discussions.

How much support was provided by MRSEC?

  • Shared

Reporting period for MRSEC

  • Period 3

PubMed: MeSH publication types

  • Journal Article

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