Polyacrylonitrile Fibers Containing Graphene Oxide

Transcription

1 [Supporting materials] Polyacrylonitrile Fibers Containing Graphene Oxide Nanoribbons An-Ting Chien, H. Clive Liu, Bradley A. Newcomb, Changsheng Xiang, James M. Tour,,#, and Satish Kumar *, School of Materials Science and Engineering, Georgia Institute of Technology, 801 Ferst Drive, NW MRDC-1, Atlanta, Georgia , United States Department of Chemistry, Department of Materials Science and NanoEngineering, and # Smalley Institute for Nanoscale Science and Technology, Rice University, 6100 Main Street, Houston, Texas 77005, United States * Corresponding author: Satish.Kumar@mse.gatech.edu. Phone: Fax:

2 1. PAN/GONR Composite Solution Polyacrylonitrile (PAN, homopolymer with viscosity average molecular weight: g/mol) was obtained from Japan Exlan Co. and dried in a vacuum oven at 100 o C for two days. PAN powder was dissolved in dimethylformamide (DMF from Sigma-Aldrich Co.) at a concentration of 15 g/100 ml) at 90 o C. Graphene oxide nanoribbon (GONR) obtained from Tour s group at Rice University was fabricated from multiwalled carbon nanotube (MWCNT, Baytubes from Bayer MaterialScience with a length of 0.2 ~ 1 μm and an outer diameter of 13 nm) according to a solution-based oxidative mechanism 1-3. GONR was dispersed in DMF at a concentration of 100 mg/300 ml using bath sonication (3510-MT, Bransonic). The GONR dispersion was later mixed with the PAN solution, and the excess solvent was evaporated using a vacuum distillation process. The GONR dispersion was added and the solvent removal process was repeated until the desired GONR concentration to PAN was equal to 1 wt%. The final solid content of PAN + GONR and the control PAN solution are listed in Table Gel Spinning PAN/GONR Composite Fibers The PAN/GONR composite fibers were spun using a spinning unit manufactured by Hills, Inc (Melbourne FL). Composite solution was maintained at 70 o C in the solution reservoir and extruded through a single-hole spinneret with a diameter of 200 m maintained at 90 o C. The spinning flow rate was 1 ml/min for both composite and control fibers. The extrudate was passed through a 25-mm air gap and then through a methanol gelation bath maintained at 50 o C. The as-spun fibers were collected with a spin draw ratio of 1 and 3 and then stored in methanol bath at 50 o C overnight. The composite fibers were subsequently drawn at room temperature and later drawn at 165 o C in glycerol. The control PAN fibers were spun with the same processing method. 2

3 3. Stabilization and Carbonization of Composite Fibers The stabilization of the composite fibers was carried out in a tube furnace (Blue M Electric) in air. A bundle of fibers was clamped at a stress of 25 MPa. The fibers were heated from room temperature up to 270 o C at a heating rate of 3 o C/min and held at 270 o C for 400 minutes. Then, they were heated up to 315 o C at a heating rate of 3 o C/min and held at 315 o C for 15 minutes. The stabilized fibers were subsequently carbonized in a tube furnace (MHI Inc.) by heating up to 1000, 1200, and 1300 o C at a heating rate of 5 o C/min in nitrogen at the same stress of 25 MPa (based on precursor fiber diameters), and the temperature was held at 1000, 1200, and 1300 o C for 5 minutes, respectively. The carbonized fibers were finally cooled down by purging nitrogen in the furnace. (1) Kosynkin, D. V.; Higginbotham, A. L.; Sinitskii, A.; Lomeda, J. R.; Dimiev, A.; Price, B. K.; Tour, J. M. Longitudinal Unzipping of Carbon Nanotubes to Form Graphene Nanoribbons. Nature 2009, 458, (2) Higginbotham, A. L.; Kosynkin, D. V.; Sinitskii, A.; Sun, Z. Z.; Tour, J. M. Lower-Defect Graphene Oxide Nanoribbons from Multiwalled Carbon Nanotubes. ACS Nano 2010, 4, (3) Rafiee, M. A.; Lu, W.; Thomas, A. V.; Zandiatashbar, A.; Rafiee, J.; Tour, J. M.; Koratkar, N. A. Graphene Nanoribbon Composites. ACS Nano 2010, 4,

4 Table S1. Processing parameters of PAN/GONR fibers and PAN fibers Sample a Draw Ratio b SDR CDR HDR TDR PAN/GONR Composite Fibers Spinning Solid Content: 18 g/100 ml Spinning Flow Rate: 1 ml/min G G G G N/A 3 G 20s G 02s Control PAN Fibers Spinning Solid Content: 15 g/100 ml Spinning Flow Rate: 1 ml/min P P P P 20s P 02s 1 2 N/A 2 a G series is composite fibers and P series is control fibers. The lower case numbers represent the total draw ratio, and the lower case letter s represents the spin draw ratio equal to one. SDR spin draw ratio, CDR draw ratio at room temperature, HDR draw ratio at 165 C, TDR total draw ratio. 4

5 Table S2. Mechanical Properties of PAN/GONR composite and control PAN fibers Sample Tensile Strength Tensile Modulus Elongation at Break (GPa) (GPa) (%) PAN/GONR Composite Fibers G ± ± ± 0.7 G ± ± ± 0.6 G ± ± ± 1.3 G ± ± ± 14.2 G 20s 0.80 ± ± ± 0.8 G 02s 0.23 ± ± ± 6.3 Control PAN Fibers P ± ± ± 0.3 P ± ± ± 0.5 P ± ± ± 0.3 P ± ± ± 0.5 P ± ± ± 4.0 5

6 Table S3. Dynamic mechanical analysis results of selected PAN/GONR and PAN fibers β c transition temperature at Sample various frequencies (Hz) a E A ( o C) kj/mole PAN/GONR Composite fibers G G G G 20s Control PAN fibers P P P P 20s a E A is activation energy calculated using the Arrhenius equation, f = Aexp( E A ), where f, A, RT R, and T are frequency, constant, gas constant, and absolute temperature, respectively. 6

7 30 μm 200 nm Number fraction GONR Width (nm) Figure S1. (a) SEM images of as-received GONRs and the number fraction of GONR width distribution. The inset image in (a) is taken under lower magnification. 7

8 3 cm Figure S2. (a) A spool of PAN/GONR composite fibers and micrograph of G 03 PAN/GONR composite fiber cross sections. 50 μm 8

9 20 μm 3 μm Figure S3. SEM images of G 30 fiber cross sections. 9

10 29 nm 9 nm 16 nm 50 nm Figure S4. (a) TEM image of G 30 PAN/GONR composite fiber with an arrow indicating the fibril axial direction and a schematic illustrating the GONR strip in the TEM image. 10

11 Number Fraction Strip Thickness (nm) 0.20 Number Fraction Void Size (nm) Figure S5. Number fraction of (a) strip width distribution and void size distribution analyzed from the SEM image of partial dissolved G 02S PAN/GONR composite fibers in Figure 4 (c). 11

12 PAN/GONR fibers are not dissolved. PAN fibers are dissolved. Figure S6. (a) G 20s PAN/GONR composite fibers and P 20s control PAN fibers after being placed in DMF for one week. 12

13 500 μm 500 nm Figure S7. SEM images of (a) G 20s PAN/GONR composite fibers and the fiber lateral surface after being placed in DMF for one week. 13

14 0.8 Tensile Strength (GPa) PAN/GONR Fibers Control PAN Fibers Draw Ratio 20 Tensile Modulus (GPa) PAN/GONR Fibers Control PAN Fibers Draw Ratio Figure S8. (a) Tensile strength and tensile modulus of selected PAN/GONR and control PAN fibers at various draw ratios (spin draw ratio equals to one). 14

15 1 μm 200 nm (c) (d) 200 nm 200 nm Figure S9. (a) SEM images of GC 1 composite carbon fiber. The carbonization process was conducted at 1300 o C for 5 minutes. ~ (d) high magnification images of selected regions in (a). 15

16 GC 1 carbonized fibers Relative Intensity (c) GS 1 stabilized fibers G 30 original fibers (degrees) Figure S10. Two dimensional WAXD diffraction patterns and the corresponding radial integrated scans of (a) GC 1 carbonized, GS 1 stabilized, and (c) G 30 original PAN/GONR composite fibers. 16