Polymersomes with Ionic Liquid Interiors Dispersed in Water

Transcription

1 Supporting Information for: Polymersomes with Ionic Liquid Interiors Dispersed in Water Zhifeng Bai and Timothy P. Lodge*,, Department of Chemistry and Department of Chemical Engineering & Materials Science, University of Minnesota, Minneapolis, Minnesota Table S1. Molecular Characteristics of Polymers Polymers a M PB (kg mol 1 ) b M PEO (kg mol 1 ) b PDI c w PEO PB PEO PB a 90% 1,2-addition in PB as determined by 1 H NMR. b Number-average molecular weight determined by 1 H NMR. c Polydispersity index (PDI) determined by size exclusion chromatography (SEC). Materials A PB PEO block copolymer, 1 provided by Dr. Kevin P. Davis, and a hydroxyl-terminated PB homopolymer, 2 were previously synthesized via anionic polymerization. The molecular characteristics of the polymers are summarized in Table S1. Rhodamine B-labeled polybutadiene (Rho PB) was previously synthesized by coupling rhodamine B acid chloride with the hydroxylterminated PB homopolymer. 2 Nile Red (NR) (99%) and Coumarin 480 (C480) were obtained from Acros and Exciton, respectively, and used as received. [EMIM][TFSI] was prepared via an anion exchange reaction 3 as follows. Equal moles of 1-ethyl-3-methylimidazolium bromide Department of Chemistry. Department of Chemical Engineering and Materials Science. S1

2 ([EMIM][Br]) (IoLiTec, 99%) (219 g) and lithium bis(trifluoromethylsulfonyl)imide ([Li][TFSI]) (3M, HQ-115) (327 g) were mixed with 250 ml distilled water and heated at 70 C with strong stirring for 1 day. The hydrophobic ionic liquid phase was separated and then washed repeatedly with distilled water, followed by passing the ionic liquid through a column of neutral alumina using dichloromethane as a solvent. The solvent was subsequently removed in a rotary evaporator and the ionic liquid was dried in a vacuum oven (~30 mtorr) at 60 C for 3 days. The ionic liquid (396 g, 89% yield) is clear and colorless, and stored in a vacuum desiccator. The structure of the ionic liquid was confirmed by 1 H NMR and its viscosity was previously characterized. 4 Vesicle Solution Preparation Vesicle solutions in [EMIM][TFSI] were prepared by a thin-film protocol. Weighed amount of block copolymer was dissolved in dichloromethane in an ampule followed by removal of the solvent by a gentle nitrogen purge and then drying at 50 C in a vacuum oven (~30 mtorr) overnight, leading to a polymer thin film. Weighed amount of [EMIM][TFSI] or a [EMIM][TFSI] solution of 0.5 mm NR or 1 mm C480 was added (0.1 wt % polymer) and the tube was sequentially evacuated and refilled with argon three times before it was sealed under an argon atmosphere. The polymer was dissolved upon stirring at 150 C for 10 h. Aqueous vesicle solutions (0.1 wt % polymer) were prepared by the same protocol, except the dissolution was conducted in a vial at room temperature. Vesicle Transfer An equal volume (1 ml) of water was added to the cloudy [EMIM][TFSI] solution of vesicles in a vial. With moderate agitation, the vesicles transferred from the ionic liquid phase to the aqueous phase in 30 min at room temperature, indicated by the clear ionic liquid phase and the cloudy aqueous phase. Upon heating, the vesicles began to transfer back to the ionic liquid phase at or above 60 ºC, and the transfer was completed in 30 min at 70 ºC. S2

3 Methods Cryogenic Transmission Electron Microscopy (cryo-tem). cryo-tem images were acquired in a JEOL 1210 TEM (120 kv) equipped with a Gatan 626 cryogenic sample holder and a Gatan 724 multiscan CCD. In a controlled environment vitrification system (CEVS), 5 aqueous cryo- TEM samples were prepared in a saturated water vapor environment at 25 ºC while [EMIM][TFSI] samples were made under ambient moisture at 40 ºC, where elevated temperature was used to reduce the viscosity of the ionic liquid samples. Several µl of 0.1 wt % polymer solution was loaded onto a carbon-coated and lacey film-supported copper TEM grid (Ted Pella) that was held by a non-magnetic tweezer. Excess solution was blotted away by a piece of filter paper and the yielded thin film of solution spanning the grid was allowed to relax for about 30 s before quickly plunging into liquid ethane (~90 K) that was cooled by liquid nitrogen. The samples were kept in liquid nitrogen before transfer to the TEM using the sample holder and imaging at 178 ºC. The images were processed with Gatan Digital Micrograph software. The standard deviation of vesicle membrane thickness was obtained from more than 50 samples from more than 10 vesicles. For the samples of vesicles with ionic liquid interiors in water, the [EMIM][TFSI]-saturated aqueous solutions were diluted 10 times with pure water before being loaded onto the grids, to reduce the electron density of the matrix and hence enhance the contrast between the matrix and the vesicle membrane and interior. Laser Scanning Confocal Microscopy (LSCM). Confocal images were recorded on an Olympus FluoView FV1000 inverted microscope with a Plan Apo N 60x 1.42NA immersion oil objective lens (Olympus). Fluorescence was collected using two sets of lasers and channels, laser 1 (λ ex. = 405 nm, diode) and channel 1 ( nm, blue), and laser 2 (λ ex. = 543 nm, HeNegreen) and channel 2 ( nm, red). The images were analyzed using Fluoview FV1000 Viewer (version 1.7a, Olympus). Ionic liquid and aqueous samples (0.025 wt % polymer) were prepared by diluting the ionic liquid solutions of the dye-loaded vesicles with pure ionic liquid and transferring the vesicles from the ionic liquid to water, respectively. S3

4 Fluorescence Spectroscopy. Fluorescence spectra were measured on a Varian Cary Eclipse fluorescence spectrophotometer at room temperature (22 ± 1 C) with excitation and emission slits of 10 nm. Aqueous samples of the dye-loaded vesicles with ionic liquid interiors (0.025 wt % polymer) were filtered through 5 µm PVDF syringe filters (Millipore) prior to measurements. UV-Visible Spectroscopy. Absorption spectra were obtained on a Varian Cary 100Bio UV- Visible spectrophotometer. Samples were prepared by mixing an equal volume of a [EMIM][TFSI] solution of 1 mm C480 or 0.5 mm NR with the PB homopolymer and equilibrating at 80 C. A 1 cm and a 1 mm quartz cell were used in the absorbance measurements of the PB phase and the [EMIM][TFSI] phase, respectively, of the biphasic PB/[EMIM][TFSI] system containing the dyes, where the PB homopolymer and [EMIM][TFSI] were used as respective background and the [EMIM][TFSI] phase was diluted gravimetrically by pure [EMIM][TFSI] until the absorbance was below 1. Dynamic Light Scattering (DLS). DLS measurements were performed on a home-made photometer outfitted with a Brookhaven BI-DS photomultiplier, a Lexel Ar + laser with a wavelength of 488 nm and a Brookhaven BI-9000 correlator. Measurements were acquired at 25.0 ± 0.2 C at seven different scattering angles between 60 and 120. Ionic liquid samples were prepared by diluting the ionic liquid solution of vesicles to wt % and subsequently filtering the solution through a 5 µm PVDF syringe filter (Millipore) into glass sample tubes with an inner diameter of 0.2 in. For the aqueous samples (0.017 wt % polymer), the vesicles in the diluted and filtered ionic liquid solution were transferred to an aqueous phase at room temperature through adding filtered water (0.2 µm GHP, Pall) to the ionic liquid solution. The cumulant method was used to extract the apparent hydrodynamic radii and the reduced second cumulant 6 and the Laplace inversion routine REPES was applied to obtain the micelle size distribution. 7 S4

5 Figure S1. Cryo-TEM images of PB-PEO vesicles initially formed in [EMIM][TFSI] and then transferred to water. Scale bars, 200 nm. Figure S2. Cryo-TEM images of PB-PEO vesicles in water 10 d after they transfer from [EMIM][TFSI] to water. Scale bars, 200 nm. S5

6 Figure S3. Decay rate vs the square of scattering vector (left panel) and hydrodynamic radius distribution (right panel) of the vesicles with [EMIM][TFSI] interiors dispersed in water, measured by DLS at 25.0 ºC. The solid line in the left panel is a linear fit of the data. References (1) Davis, K. P.; Lodge, T. P.; Bates, F. S. Macromolecules 2008, 41, (2) Bai, Z.; Lodge, T. P. J. Phys. Chem. B 2009, 113, (3) Bonhote, P.; Dias, A.-P.; Papageorgiou, N.; Kalyanasundaram, K.; Gratzel, M. Inorg. Chem. 1996, 35, (4) Bai, Z.; He, Y.; Lodge, T. P. Langmuir 2008, 24, (5) Bellaire, J. R.; Davis, H. T.; Scriven, L. E.; Talmon, Y. J. Electron Micros. Tech. 1988, 10, (6) Koppel, D. E. J. Chem. Phys. 1972, 57, (7) Jakes, J. Collect. Czech. Chem. Commun. 1995, 60, S6

7 Complete Ref. 9 in the text: Percec, V.; Wilson, D. A.; Leowanawat, P.; Wilson, C. J.; Hughes, A. D.; Kaucher, M. S.; Hammer, D. A.; Levine, D. H.; Kim, A. J.; Bates, F. S.; Davis, K. P.; Lodge, T. P.; Klein, M. L.; DeVane, R. H.; Aqad, E.; Rosen, B. M.; Argintaru, A. O.; Sienkowska, M. J.; Rissanen, K.; Nummelin, S.; Ropponen, J. Science 2010, 328, S7