Supporting Information

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1 Supporting Information Self-cleaning membranes from comb-shaped copolymers with photoresponsive side groups Papatya Kaner 1, Xiaoran Hu 2, Samuel W. Thomas III 2, Ayse Asatekin 1,* 1 Department of Chemical and Biological Engineering, Tufts University, Medford, MA 2155, USA 2 Department of Chemistry, Tufts University, Medford, MA 2155, USA * Corresponding author. Tel.: ; Fax: address: Ayse.Asatekin@tufts.edu (Ayse Asatekin) S-1

2 Supporting Information. Section S1: Experimental details for Dynamic Light Scattering experiments and molar mass calculations. Section S2: Elemental analysis results. Section S3: Surface morphology of the membranes by Scanning Electron Microscopy. Section S4: Protein release in phosphate buffered saline solution and membrane stability. Section S5: Self-cleaning tests on M-SPMA2 and base PVDF4R membrane. S1. Molar mass characterization S1.1. Molar mass characterization of P(ACN-r-BBEM) copolymers In order to estimate the molar masses of the backbone copolymers, we performed dynamic light scattering (DLS) (Malvern Zetasizer Nano). A 35 mw red diode laser with a nominal wavelength of 633 nm was used as the light source. All the measurements were done on copolymer solutions in DMF at a concentration of 1 mg/ml at a scattering angle of 9 and a temperature of 25 C, which was controlled by means of a thermostat. A.2 μm filter was used to remove dust before light scattering experiments. After stabilization of samples for two minutes, three measurements were performed for each copolymer ratio. The effective hydrodynamic radii values obtained (Table S1) were used in determining the relative molar masses based on polyacrylonitrile standards in DMF by following the calculations below. The intrinsic viscosity derived from Einstein equation is [ηη] = 5 2 NN AAVV h MM (SS1) NN AA : Avogadro number VV h : Hydrodynamic volume MM: Molar mass The intrinsic viscosity can also be represented by Mark-Houwink equation [ηη] = KKMM aa (SS2) where KK and aa are Mark-Houwink parameters dependent on polymer solvent interactions. 3 Plugging the hydrodynamic volume of a sphere VV h = 1/6ππDD h into Eq. S1 and equating it to Eq. S2 gives MM aa+1 = NN AA ππdd h (SS3) KK For PAN in DMF at 25 o C, the Mark-Houwink parameters are KK = 2.43xx1 2 and aa =.75. Using these values in solving Eq. S3, we can obtain the molar masses tabulated in the rightmost column of Table S1. S-2

3 Table S1. Molar mass calculations using Eq. S3. Sample 15:1 P(ACN-r-BBEM) 144:1 P(ACN-r-BBEM) Sample ID Dh (nm) Dh (cm) M a+1 M (g/mol) x x x x x x x x x1 4 Average x x x x x x x x x x x x1 4 Average x x x1 4 The macroinitiator 15:1 P(ACN-r-BBEM) molar mass: 46,7 g/mol The macroinitiator 144:1 P(ACN-r-BBEM) molar mass: 33,3 g/mol S1.2. Molar mass characterization of PAN-g-SPMA copolymers The molar masses of the comb PAN-g-SPMA copolymers were estimated using the obtained molar mass of the backbone copolymers; 4.67 x 1 4 g/mol and 3.33 x 1 4 g/mol for 15:1 and 144:1 P(ACN-r-BBEM) copolymers, respectively. Using the backbone:side-chain weight ratios of 47:53 and 4:6 for SPMA12 and SPMA2 copolymers, their molar masses were calculated to be 9.91 x 1 4 g/mol and 8.33 x 1 4 g/mol. S2. Elemental analysis Elemental analysis was performed by NSL Analytical Services, Inc. Table S2. Elemental analysis results. 15:1 P(ACN-r-BBEM) Br content (by w.t.) Cl content (by w.t.).78 % / Br: 1.22% SPMA12 <.2 %.11 % Cl:.36% Calculated Br or Cl content based on NMR results (by w.t.) S-3

4 S3. Surface morphology by SEM Figure S1. Surface SEM images of M-SPMA12 membrane at (a) as-coated; (b) UV-irradiated; and (c) visible-irradiated states, and M-SPMA2 membrane at (d) as-coated; (e) UV-irradiated; and (f) visible-irradiated states. S4. Protein release in PBS solution and membrane stability To determine any potential release of UV-induced MC form from the membrane surface into the PBS solution and to follow protein release from the membrane surface, we performed timedependent UV irradiation experiments on a pre-fouled as-coated membrane surface covered with a thin layer of PBS solution. First, the BSA foulant solution (1 g/l BSA in PBS) was filtered for two hours after overnight stabilization with DI water at 3 psi (.21 MPa). After that, the membrane surface covered with a thin layer of PBS solution (3 ml) was exposed to UV light for 5 min, and the PBS solution was analyzed with UV-Vis spectrophotometer to determine contents released from the membrane surface. The PBS solution was poured back onto the membrane surface, and this procedure was repeated after each 5 min UV exposure, conducted for a collective exposure period of 28 min. S-4

5 M-SPMA12 2 M-SPMA2 Absorbance.5 28 min min Absorbance min min Wavelength (nm) Wavelength (nm) Figure S2. Time-dependent UV irradiation on a pre-fouled as-coated surface of (a) M-SPMA12; (b) M-SPMA2. For testing stability of M-SPMA12 during PBS filtration, we ran a sequential water-pbs-water filtration (Figure S3) following the steps: (1) Filter DI water for 2h to determine the initial flux, (2) filter PBS solution for 24h, and (3) filter DI water for 2h again to compare fluxes before and after PBS filtration. Permeance in Figure S3 during PBS filtration show data recorded in the last two hours of the PBS run. Permeance (L/m 2.h.bar) M-SPMA12 in MC form W A TER PBS W A TER Time (min) Figure S3. Consecutive filtration of water-pbs-water through the M-SPMA12 membrane. S-5

6 S5. Self-cleaning tests on M-SPMA2 and base PVDF4R membranes Permeance (L/m 2.h.bar) UV VIS UV M-SPMA2 W A TER BSA W A TER W A TER BSA W A TER W A TER BSA W A TER W A TER BSA W A TER Time (min) Figure S4. Fouling resistance and self-cleaning performance of the M-SPMA2 membrane. PVDF4R Permeance (L/m 2.h.bar) UV W A TER BSA W A TER W A TER Time (min) Figure S5. Fouling resistance and self-cleaning performance of base PVDF4R membrane. S-6