Supporting Information Semipermeable Microcapsules with a Block Polymer-templated Nanoporous Membrane Jaehoon Oh,, Bomi Kim,, Sangmin Lee, Shin-Hyun Kim,*, Myungeun Seo*, Graduate School of Nanoscience and Technology, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea Department of Chemical and Biological Engineering, KAIST, Daejeon 34141, Korea Equally contributed. *To whom should be addressed: kim.sh@kaist.ac.kr (S.-H. K.); seomyungeun@kaist.ac.kr (M. S.)
Table of Contents S1. Materials S2. Preparation of crosslinked nanoporous PS monoliths S2.1 Methods S2.2 Synthesis of PLA-CTAs S2.3 Synthesis of crosslinked nanoporous PS monoliths S3. Preparation of microcapsules with a nanoporous membrane S4. Characterization of microcapsules with nanoporous membrane S5. Supporting references
S1. Materials Unless otherwise noted, all the chemicals were used as received. d,l-lactide was kindly provided by Purac (Amsterdam, Netherlands), and stored under nitrogen in a glovebox after recrystallization from toluene. 1,8-Diaza-bicyclo[5.4.0]undec-7-ene (DBU) was purchased from TCI (Tokyo, Japan) and also stored in a glovebox. Styrene (99%) and divinylbenzene (DVB, 80% (tech.)) were purchased from Sigma-Aldrich (St. Louis, MO) and purified by passing through a basic alumina column prior to polymerization. Octadecyltrimethoxysilane, poly(vinyl alcohol) (PVA, M w 13-23 kg mol -1 ), sulforhodamine B, and fluorescein isothiocyanate (FITC)-tagged dextrans with seven different molar masses (4, 10, 20, 40, 70, 150, and 500 kg mol -1 ) were also purchased from Sigma-Aldrich. 2- [Methoxy(polyethyleneoxy) propyl]trimethoxysilane was purchased from Gelest, Inc.. Azobisisobutyronitrile (AIBN, 98%) and methanol ( 99.8%) were purchased from Junsei (Tokyo, Japan). AIBN was purified by recrystallization in methanol and stored at -20 C. All the HPLC grade solvents were purified using a solvent purification system (C&T International, Suwon, Korea). HPLC grade toluene and dichloromethane (DCM) were purchased from Burdick & Jackson (Morristown, NJ ) and J. T. Baker (Center Valley, PA), respectively. Other laboratory chemicals were purchased from Daejung. 2-Hydroxyethyl 2- (((dodecylthio)carbonothioyl)-thio)-2-methylpropanoate (CTA-OH) was prepared following literature procedure. 1 S2. Preparation of crosslinked nanoporous PS monoliths S2.1. Methods 1 H nuclear magnetic resonance (NMR) spectroscopy was conducted using a Bruker Avance 400 MHz spectrometer (Billerica, MA) using the residual NMR solvent signal as an internal reference. Size exclusion chromatography (SEC) was performed in chloroform at 35
C on an Agilent 1260 Infinity system (Santa Clara, CA) equipped with a refractive index detector and three PLgel 10 µm Mixed-B columns in series with a molar mass range 500 10,000,000 g mol -1. The molar masses of the polymers were calculated relative to linear polystyrene standards (EasiCal) purchased from Agilent Technologies. Fourier transform infrared (FTIR) spectra were obtained on a Bruker Alpha FTIR spectrometer using a Platinum ATR (attenuation total reflection) single reflection module. Synchrotron Smallangle X-ray scattering (SAXS) experiments were performed at 9A beam lines in the Pohang Accelerator Laboratory (PAL). A monochromatized X-ray radiation source of 19.96 kev (0.0621 nm) and 20.11 kev (0.0617 nm) with the sample-to-detector distance of 6.47 m and 6.46 m was used. Scattering intensity was monitored by a Mar 165 mm diameter CCD detector with 2048 2048 pixels. The two-dimensional scattering patterns were azimuthally integrated to afford one-dimensional profiles presented as scattering vector (q) versus scattered intensity, where the magnitude of scattering vector is given by q = (4π/λ) sinθ. Scanning electron microscope (SEM) images were collected on a Hitachi S-4700 FE-SEM (Schaumburg, IL) instrument with a 5 kv accelerating voltage and a upper secondary electron detector. Samples were coated with Os prior to imaging. S2.2. Synthesis of PLA-CTAs Polylactide macro-chain transfer agents (PLA-CTAs) were synthesized by ring opening transesterification polymerization (ROTEP) of d,l-lactide in the presence of CTA- OH as an initiator and DBU as a catalyst. The protocol has been previously reported in detail elsewhere. 1 The synthesized PLA-CTAs are summarized in Table S1. 1 H NMR spectra and SEC traces of the PLA-CTAs are also shown in Figure S1 and S2, respectively.
Table S1. Characterization of PLA-CTAs Entry PLA-CTA M n,nmr (kg mol -1 ) a M n,sec (kg mol -1 ) b Ð b 1 PLA-CTA-13 13 20 1.06 2 PLA-CTA-24 24 34 1.08 3 PLA-CTA-35 35 43 1.08 a Calculated by 1 H NMR end group analysis b Estimated based on linear polystyrene standards Figure S1. 1 H NMR (400MHz, CDCl 3, 20 C) spectra of PLA-CTA-13, PLA-CTA-24, PLA- CTA-35.
Figure S2. SEC traces of PLA-CTA-13, PLA-CTA-24, PLA-CTA-35. S2.3. Synthesis of crosslinked nanoporous PS monoliths Bulk copolymerization of styrene and DVB in the presence of PLA-CTA to produce a monolithic crosslinked PLA-b-P(S-co-DVB) precursor was conducted slightly modifying the literature procedure. 2 Synthesis of the crosslinked PS-b-PLA precursor with PLA-CTA- 13 (Entry 1 of Table S2) is given here as an exemplary case. A solution of PLA-CTA-13 (0.3012 g, 23.1 µmol) and AIBN (0.0038 g, 23.1 µmol) in a mixture of styrene (0.59 ml, 5.1 mmol) and DVB (0.18 ml, 1.3 mmol) was prepared and placed in a vial. The mixture was placed in the oil bath preset at 70 C. After heating for 24 h, the polymerization mixture was
cooled to rt and the vial was broken. The resulting yellow transparent solid was allowed to evaporate volatiles in ambient condition (0.9821 g, 98% yield). Other PS-b-PLA precursors were produced using different PLA-CTAs following the above protocol, fixing the molar ratio of styrene to DVB as [styrene]:[dvb] = 4:1 and the weight fraction of PLA-CTA in the polymerization mixture as 30%. The [PLA-CTA]:[AIBN] was adjusted as 1:1.8 for PLA- CTA-24 and 1:2.7 for PLA-CTA-35 to accelerate polymerization. Formation of the disordered bicontinuous morphology via the PIMS process was evidenced by SAXS, where a broad principal peak followed by the second-order shoulder was observed from all three samples (Figure S3). Crosslinked nanoporous PS monoliths were derived from the crosslinked PLA-b- P(S-co-DVB) precursors by basic PLA etching following the literature procedure. 2 Complete removal of PLA was confirmed by FTIR analysis (Figure S4), where the vibrational frequency at 1747 cm -1 corresponding to C=O stretching of PLA disappeared after etching. Successful generation of 3D continuous nanopore structure was clearly observed by SEM (Figure S5) and nitrogen sorption isotherm measurements (Figure S6). Table S2 summarizes characterization data of the crosslinked PLA-b-P(S-co-DVB) precursors and corresponding nanoporous PS by SAXS and nitrogen sorption isotherm measurements. Table S2. Characterization of crosslinked PLA-b-P(S-co-DVB) precursors and nanoporous PS Entry PLA-CTA Precursor Nanoporous PS D (nm) a d BJH (nm) b S BET (m 2 g 1 ) c V (ml g 1 ) d 1 PLA-CTA-13 21.7 5.92 198.83 0.35 2 PLA-CTA-24 25.1 7.63 155.94 0.34 3 PLA-CTA-35 33.4 9.18 119.94 0.32 Domain spacing determined from the position of the principal scattering peak in SAXS data b Mean pore diameter determined by BJH analysis of the desorption branch of a nitrogen sorption isotherm c Surface area determined by multipoint BET analysis from the points between 0.05 < P/P 0 < 0.35 in a nitrogen sorption isotherm
d Pore volume calculated from the point P/P 0 = 0.95 Figure S3. SAXS data of the crosslinked PLA-b-P(S-co-DVB) precursors (dashed line) and nanoporous monoliths (solid line) prepared with different PLA-CTAs.
Figure S4. FTIR spectra of the crosslinked PLA-b-P(S-co-DVB) precursor (black) and the corresponding crosslinked nanoporous PS monolith after PLA removal (red). The precursor was prepared from PLA-CTA-13.
Figure S5. SEM images of fractured surfaces of the nanoporous monoliths prepared with different PLA-CTAs. Scale bars represent 200 nm. (a) PLA-CTA-13. (b) PLA-CTA-24. (c) PLA-CTA-35.
Figure S6. (a) Nitrogen adsorption isotherms of the nanoporous monoliths recorded at 77.3 K. Filled squares: adsorption. Empty circles: desorption. (b) Pore size distributions based on BJH analysis of the desorption branches.
S3. Preparation of microcapsules with a nanoporous membrane Figure S7. (a) Single- and double-emulsion drops in a collection liquid. (b) Single-emulsion drops and double-emulsion drops which are separated by exploiting their density difference. Single- and double-emulsion drops are denoted with black and white arrows, respectively.
Figure S8. Evolution of PLA-b-PS from the polymerization mixture of PLA-CTA-24, styrene which [PLA]:[S] = 1:513 and AIBN (1.8 eq to PLA-CTA-24) at 70 C without degassing. The time lapse of polymerization for each sample is indicated in the legend. The polymers were obtained by cooling the polymerization mixture to RT, precipitating in methanol, and filtration. While a shift of the main peak to smaller elution time indicates growth of PS block off the end of PLA-CTA to form PLA-b-PS as polymerization proceeds, appearance of a new peak at higher elution time indicates formation of homops which is in equilibrium with PLAb-PS in the polymerization mixture via the RAFT mechanism. (a) SEC trace overlay. (b) 1 H NMR spectrum overlay.
Figure S9. Evolution of PLA-b-P(S-co-DVB) from the polymerization mixture of PLA-CTA- 24, styrene, DVB, and AIBN (1.8 eq to PLA-CTA-24) at 70 C without degassing. The time lapse of polymerization for each sample is indicated in the legend. The polymers were obtained by cooling the polymerization mixture to RT, precipitating in methanol, and filtration. (a) SEC trace overlay. (b) 1 H NMR spectrum overlay.
Table S3. Polymerization kinetics at high AIBN loading Styrene polymerization kinetics in the presence of PLA-CTA Reaction time (min) Conversion a (%) Integration ratio b M n,ps c (kg mol -1 ) 0 0 0 0 0 120 12 0.99 6.9 22 180 27 2.2 16 39 S/DVB copolymerization kinetics in the presence of PLA-CTA Reaction time (min) Conversion a (%) Integration ratio b M n,p(s-co-dvb) c (kg mol -1 ) w PS c (%) w P(S-co-DVB) c (%) 0 0 0 0 0 60 0 0 0 0 110 6.1 0.49 3.8 14 a Double bond conversion calculated from 1 H NMR spectra of quenching samples b Area of the peak appearing at 6.8 7.26 ppm corresponding to aromatic protons normalized by the peak area at 4.8 5.4 ppm, which corresponds to the methine proton of PLA c Weight fraction of the polystyrenic block in the block copolymer calculated from the integration ratio
Figure S10. FTIR spectra of the polymerized microcapsule (black) and the corresponding microcapsule with a nanoporous membrane after PLA etching (red). The polymerized microcapsule was prepared with PLA-CTA-13.
Figure S11. SEM images of microcapsules with a nanoporous membrane prepared from PLA-CTA-13. (a) Dried microcapsules and (b) surface morphology of the nanoporous membrane. (c) Cross-section of the nanoporous membrane which shows nanopores percolating through the entire thickness of the membrane.
S4. Characterization of microcapsules with nanoporous membrane 1.0 0.8 Sulforhodamine B 4 kda FITC-dextran 10 kda FITC-dextran 20 kda FITC-dextran 70 kda FITC-dextran 0.6 I/I max 0.4 0.2 0.0 0.0 0.2 0.4 0.6 0.8 1.0 C/C max Figure S12. Fluorescence intensity as a function of dye concentration for sulforhodamine B (squares), FITC-tagged dextrans with M w 4 kg mol -1 (circles), 10 kg mol -1 (triangles), 20 kg mol -1 (inverted triangles), and 70 kg mol -1 (diamonds). The values of C max are 10-4 M, 10-3 M, 2 10-3 M, 2 10-3 M, and 2.5 10-4 M for sulforhodamine B, FITC-tagged dextrans with M w 4 kg mol -1, 10 kg mol -1, 20 kg mol -1, and 70 kg mol -1, respectively and each value of I/I max is based on 10 times of measurement. The linear relation between the intensity and concentration was observed for all the dye molecules.
Figure S13. Temporal dependence of normalized fluorescence intensity in the core of microcapsules for sulforhodamine B (squares), FITC-tagged dextrans with M w 4 kg mol -1 (circles), 10 kg mol -1 (triangles), 20 kg mol -1 (inverted triangles), and 70 kg mol -1 (diamonds). Fits with equation (1) are shown by solid lines. The data up to 3000 s is identical to that shown in Figure 2c.
S5. Supporting references 1. Oh, J.; Seo, M. ACS Macro Lett. 2015, 4, 1244-1248. 2. Seo, M.; Hillmyer, M. A. Science 2012, 336, 1422-1425.