Electronic Supplementary Material (ESI) for Soft Matter This journal is © The Royal Society of Chemistry 2012 Design Principles for Supercritical CO2 Viscosifiers Stephen Cummingsa, Dazun Xingb, Robert Enickb, Sarah Rogersc, Richard Heenanc, Isabelle Grillod and Julian Eastoea* School of Chemistry, University of Bristol, Cantock’s Close, Bristol, BS8 1TS, UK E-mail:Julian.Eastoe@bristol.ac.uk b National Energy Technology Laboratory IAES, and Department of Chemical and Petroleum Engineering, Swanson School of Engineering University of Pittsburgh, 3700 O'Hara Street, Pittsburgh PA 15261, USA c ISIS-CCLRC, Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX, U.K d Institut Max-von-Laue-Paul-Langevin, BP 156-X, F-38042 Grenoble Cedex, France, a By varying the F7H4 surfactant counterion hydrated radius, it has been possible to create a range of non-spherical micelle architectures in supercritical CO2 (scCO2), which enhance viscosity. Furthermore this array of morphologies can be related to measurements performed at the air-water interface. Electronic Supplementary Material (ESI) for Soft Matter This journal is © The Royal Society of Chemistry 2012 Surfactant Synthesis: Synthesis of the Grignard N-butylmagnesium Bromide: The reaction was performed under N2. A few drops of 1-bromobutane (total quantity 35 cm3, 330 mmol, held in a dropping funnel) were added to a dispersion of magnesium turnings, with a single crystal of iodine, in 100 ml of diethyl ether. The reaction was gently activated by means of a hot-air gun, and weak effervescence was observed at the magnesium surface, with further addition of bromobutane the reaction accelerated, with white flocculation appearing in the solution and ether starting to reflux. At this stage the remaining bromobutane was diluted with 30 cm 3 of diethyl ether, and added slowly over a half hour or so. Once the addition of bromobutane was completed the reaction mixture was refluxed at 50 °C for 2 and half hours. After this the reaction was cooled to room temperature and allowed to settle down. Synthesis of the pentadecafluoro-5-dodecanone: The reaction was performed under N2. A 250 cm3 pressure equalising dropping funnel containing a solution of pentadecafluorooctanoic acid in 100 cm3 of diethyl ether was fitted to the apparatus mentioned above. The solution was then added drop-wise over an hour at room temperature to the previously formed Grignard reagent whilst stirring. After refluxing the reaction mixture for 4 and half hours, the reaction was then cooled down to 0 °C, and acidified with 200 cm3 of 10% HCl solution. Excess magnesium was then filtered off, the upper yellow organic phase separated, whilst the lower aqueous phase was extracted with diethyl ether (3 × 50 cm3). All ether extracts were combined and washed with saturated aqueous solution of sodium hydrogen carbonate (2 × 75 cm3) and saturated aqueous solution of sodium chloride. The resulting organic phase was then dried over magnesium sulfate. The remaining solvent was then rotary evaporated, with resulting yellow oil then being vacuum distilled to high purity to give a light yellow colored oil. Synthesis of the pentadecafluoro-5-dodecanol: Sodium borohydride (3.5g, 91 mmol, 1.15 equiv.) was added portion-wise to a solution of ketone (40g 79 mmol, 1.0 equiv) in 300 cm3 of ethanol at 0 °C whilst stirring. The reaction was left for 3 hours at Electronic Supplementary Material (ESI) for Soft Matter This journal is © The Royal Society of Chemistry 2012 0 °C and then for one hour at room temperature. At the end of the reaction most of solvent was evaporated and the resulting mixture was neutralised at 0 °C with 50% acetic acid solution. With aid of ethanol water was removed by rotary evaporation and the remaining solution was dissolved in 250 cm3 of diethyl ether. After repeated washing of the organic layer with water (1 × 50 cm3), sodium hydrogen carbonate (4 × 75 cm3), and with water again (2 × 50 cm3), the crude alcohol was obtained by rotary evaporation. Further water removal was achieved azeotropically by rotary evaporation with toluene. The alcohol product was a white oil which, on cooling, produced white crystals. Synthesis of Sodium pentadecafluoro-5-dodecyl sulfate – F7H4: Controlled addition at 0 °C of chlorosulfonic acid (9.0 cm3, 135 mmol, 1.9 equiv) to 60 cm3 of pyridine produced a white solid. A solution of pentadecafluoro-5-dodecanol in 55 cm3 of pyridine was added to this dispersion at 0 °C and with stirring,. The reaction mixture was slowly warmed to 60 °C until it turned transparent yellow (after ~ 1 hour). The reaction mixture was then quenched in ~600 cm3 of ice cooled, saturated sodium carbonate solution and left for 1 hour and half, allowing for sodium hydrogen carbonate salts to precipitate out. The said salts were filtered, and the product extracted with butanol (3 × 75 cm3). The aqueous layers were separated and the pyridine and butanol phases combined. Solvent evaporation yielded the crude surfactant, which was purified using a minimum amount of distilled dry acetone. Electronic Supplementary Material (ESI) for Soft Matter This journal is © The Royal Society of Chemistry 2012 Figure S1: 1H NMR of F7H4 and spectral assignments of M-F7H4 Electronic Supplementary Material (ESI) for Soft Matter This journal is © The Royal Society of Chemistry 2012 HP SANS using a custom-made pressure cell Figure S2: Schematic of the HP-SANS pressure cell system. The SPM25 pressure cell was designed by Thar Technologies, Inc. (Thar Instruments, 575 Epsilon Drive, Pittsburgh, PA 15238) specifically for HP-SANS measurements in scCO2, based on a commercially available SPM20 unit. The cell incorporates two sapphire windows mounted 180° to each other. Figure S1 shows a schematic diagram of the cell. The viewed diameter of the windows is 17.35 mm and the path length between the inside faces of the windows is adjustable (from 0 – 19 mm). With the top loaded magnetically coupled stirrer/propeller in place the maximum working pressure is 413 bar (5700 psia). Pressurised CO2 is injected into the cell via a syringe pump; further pressure adjustments can be made via a movable piston driven by a hydraulic pump. Vessel pressure is detected by a transducer mounted in the side of the cell body. Both temperature and pressure are monitored remotely by a PLC controller, enabling remote adjustment of these parameters during neutron experiments. Electronic Supplementary Material (ESI) for Soft Matter This journal is © The Royal Society of Chemistry 2012 Air-water surface tension behaviour of Na-F7H4. Figure S3: Surface tension curve for Na-F7H4 with a quadratic fit to the pre-cmc region. Electronic Supplementary Material (ESI) for Soft Matter This journal is © The Royal Society of Chemistry 2012 SANS data fitting: All SANS profiles were fitted using the interactive FISH program 1 written by R. K. Heenan, which employs a standard iterative least-squares method. Spheres The form factor for polydisperse spheres, each with radius R, is defined as follows2: (1) (2) Where ji(QR) is a first order spherical Bessel function and g(R) is (in this case) defines a Schultz distribution of homogeneous spheres: (3) Where the width parameter, Z > -1, R is the mean of the distribution and polydispersity is defined by an RMS deviation σ = R / (Z+1)1/2. Parameters fit in FISH were sphere radius rD2O, polydispersity index σ, and the Shultz scale factor given by SF = 10-24 φagg(ρ)2 where φagg is the aggregate volume fraction and ρ is the contrast step between solvent medium and surfactant aggregates. Using these calculated values, SANS fitting was carried out to fixed values of r and σ in order to obtain a value for φagg. Due to natural uncertainties in measured absolute intensity (±5%), the exact value for ρ, and also the recognized close coupling in the fitting models between scale factor and aggregate radius in polydisperse samples, this calculated φagg should only be treated as a guide. Ellipsoids The scattering law for ellipsoids of radii r1, r2 and L with L = X × r (where X is the aspect ratio) is summarised in equations 4-6. It requires a numerical integration of P(Q) over angle α. 3 Electronic Supplementary Material (ESI) for Soft Matter This journal is © The Royal Society of Chemistry 2012  2 (4) P(Q)   F 2 Q, r , X ,  sin d 0 (5)  r , X ,    r sin 2   X 2 cos 2  (6) V   1 2 4XrD3 2O 3 Parameters fitted in FISH were ellipsoid cross section radius rD2O, axial ratio X and scale factor given 2 2 by n pV ( ) where np is aggregate number density. Above an aspect ratio X ~ 7 the ellipsoid form factor tends to that for a rigid homogeneous cylinder (given below). Cylinders For N randomly oriented rods of length L and cross-sectional radius R, the form factor P(Q) is given by 7-9 below.4  2 P(Q)  N  F 2 (Q) sin( )d (7) 0 (8) F (Q)  ( )V sin( 1 QL cos  ) 2 J (Qr sin  ) 2 1 1 QL cos  Qr sin  2 V  rD 2O L 2 (9) J1(x) is the first order Bessel function of the first kind and integration is carried out numerically over angle γ between the Q vector and the axis of the rod. Parameters fitted in FISH were D 2O radius rD2O, 24 2 rod length L and the scale factor given by 10  ( ) where  is aggregate volume fraction and  is the contrast step (known). Electronic Supplementary Material (ESI) for Soft Matter This journal is © The Royal Society of Chemistry 2012 Structure factor S(Q) for F7H4 in D2O Surfactant rF7H4 RF7H4 X tF7H4 S(Q) Li-F7H4 15.7 - - - 26.21 Hayter Penfold 14.0 0.081 Na-F7H4 15.9 - - - 3.26 Hayter Penfold 12.0 0.080 K-F7H4 16.5 38 2.3 - 23.56 Hayter Penfold 20.0 0.078 Rb-F7H4 234 - - 0.0313 Hard Sphere 0.075 28.2 Charge q AKK - Table S1: Structural parameters for F7H4-D2O systems including S(Q) contributions and type, and the charge and AKK used in these models. Phase stability of Na-F7H4 scCO2 systems: Figure S4: Pressure-temperature phase diagrams of w/c microemulsion systems for Na-F7H4 in scCO2 with water content, w = [H2O]/[surfactant]. Electronic Supplementary Material (ESI) for Soft Matter This journal is © The Royal Society of Chemistry 2012 Small Angle Neutron Scattering (SANS) of F7H4-scCO2 systems Figure S5: HP-SANS profiles for w/c microemulsion systems of K-F7H4, at 4.4 wt% in scCO2 at 400 bar, 40 °C (w = [D2O]/[surfactant]). Fitted scattering laws are shown as lines with derived parameters listed in Table 3 (main paper). Electronic Supplementary Material (ESI) for Soft Matter This journal is © The Royal Society of Chemistry 2012 Figure S6: HP-SANS profiles for w/c microemulsion systems of Rb-F7H4, at 4.4 wt% in scCO2 at 400 bar, 40 °C (w = [D2O]/[surfactant]). Fitted scattering laws are shown as lines with derived parameters listed in Table 3 (main paper). High pressure Viscometry Relative viscosity can be estimated by5: (10) Where KH5: (11) With Perot2 being described by5: (12) Where ύ is the shear rate (~ 11000 s-1) and Drot is the rotational diffusion coefficient6,7: Electronic Supplementary Material (ESI) for Soft Matter This journal is © The Royal Society of Chemistry 2012 (13) Where γ║ and γ┴ are the particle end-effect corrections and the validity of these expressions holds for different ranges of the aspect ratio. The expressions used here are those of Tirado et al.8, which are valid for aspect ratios in the range of 2 < L/d (X) < 30. CO2 neat viscosity, η0 = 0.00011 Pa s9,10 Species Li-F7H4 Na-F7H4 K-F7H4 w 15. 0 12. 5 15. 0 Aspec t Ratio, Xmic ηmic/ηCO2 Intrinsic viscosity, [η] Calc ηrel Drot / s−1 Perot KH 4.2 1.18 4.9 1.24 3888367 0.002828951 0.4 10.5 1.76 14.6 1.82 696168 0.01580078 0.4 3.0 1.11 3.8 1.18 4146457 0.002652867 0.4 References (1) Heenan, R. K. Rutherford Appleton Laboratory Report Rutherford Appleton Laboratory, 1989. (2) Kotlarchyk, M.; Chen, S.-H. The Journal of Chemical Physics 1983, 79, 2461. (3) Guinier, A. Ann. Phys. 1939, 12, 161. (4) Fournet, G. Bull. Soc. Fr. Mineral. Crist. 1951, 74, 37. (5) Wierenga, A. M.; Philipse, A. P. Colloids Surf., A 1998, 137, 355. (6) Lehner, D.; Lindner, H.; Glatter, O. Langmuir 2000, 16, 1689. (7) Broersma, S. The Journal of Chemical Physics 1960, 32, 1626. (8) Tirado, M. M.; Martinez, C. L.; Torre, J. G. d. l. The Journal of Chemical Physics 1984, 81, 2047. (9) Fenghour, A.; Wakeham, W. A.; Vesovic, V. Journal of Physical and Chemical Reference Data 1998, 27, 31. (10) Xiong, Y.; Kiran, E. Polymer 1995, 36, 4817.