Supporting Information for Polypyrrole/Agarose based Electronically Conductive and Reversibly Restorable Hydrogel Jaehyun Hur, Kyuhyun Im, Sang Won Kim, Jineun Kim, Dae-Young Chung, Tae-Ho Kim, Kyoung Ho Jo, Jong Hoon Hahn, Zhenan Bao, Sungwoo Hwang, and Nokyoung Park * Department of Chemical and Biological Engineering, Gachon University, Seongnam, Gyeonggi 461-701, Republic of Korea Frontier Research Laboratory, Samsung Advanced Institute of Technology, Samsung Electronics, Yongin, Gyeonggi, 446-712, Republic of Korea Department of Chemistry, Pohang University of Science & Technology, Pohang 790-784, South Korea Department of Chemical Engineering, Stanford University, California 94305, USA * Corresponding author e-mail: n2010.park@samsung.com S1
S1. Quantification of polymerization by thermogravimetric analysis (TGA) We performed the thermogravimetric analysis (TGA) to quantify the amount of polymerized pyrrole in the hybrid gel which is helpful to better understand the polymerization process in the gel. For the different pyrrole concentration (cpyrrole = 15, 75, and 450 mm), the weight fractions of PPy were calculated to be 3.8, 18.8, and 56.4%. The systematically increasing amount of PPy with increasing pyrrole concentration suggests the polymerization of pyrrole is not significantly hindered even inside of the gel network. 100 Weight (%) 80 60 40 20 A-gel 15mM 75mM 450mM PPy 0 100 200 300 400 500 600 Temperature ( o C) Figure S1. Thermogravimetric analysis (TGA) for A-gel, PPy, and APY gel with c pyrrole = 15, 75, and 450 mm. S2
S2. Measurement of differential scanning calorimetry (DSC) Glass transition temperature of APY gel at different pyrrole concentrations were characterized by the DSC measurement (Fig. S2). Pure PPy showed the glass transition at ~ 97 C from a broad endothermic dip which is in good agreement of the previous report. 1 In contrast, A-gel had a relatively sharper endothermic dip at ~ 116 C. As the pyrrole concentration increases, the glass transition temperature (Tg) of APY gel gradually shifted to the higher temperature. Specifically, the T g of APY gel at C pyrrole = 15, 75, and 450 mm were 114, 112, and 108 C as shown in Fig. S1a. It can be concluded that T g of APY gel reflects the ratio of A-gel to PPy. Heat flow (W/g) 1.5 1.0 0.5 0.0-0.5-1.0-1.5-2.0 A-gel 15mM 75mM 450mM PPy Glass transition temperature ( o C) 120 110 100 90 A-gel 15mM 75mM 450mM PPy 40 60 80 100 120 Temperature ( o C) Figure S2. Analysis of APY gel at different pyrrole concentrations and comparison with A-gel and PPy from DSC. S3
S3. Comparison of surface roughness between A-gel and APY gel with AFM Figure S3. AFM image of A-gel (a c) and APY gel (d f). a, d, Height image, b, e phase image, c, f, 3D height of A-gel and APY gel, respectively. The image size is 4 µm ⅹ 4 µm. S4
S4. EDX analysis of APY gel at different pyrrole concentration Figure S4. EDS mapping of APY gel at different pyrrole concentration. a, 15 mm, b, 30 mm, and c, 75 mm. The image at different row shows original (upper), nitrogen atom based (middle), and carbon atom based (bottom) image, respectively. S5
S5.Raman spectroscopy of A-gel, PPy, and APY gel. Fig.S5presents the Raman spectrums of A-gel, PPy, and APY gel, respectively. In APY gel, the characteristic peaks at 1581 cm -1 and shoulder at 1372 cm -1 were identical to the PPy. The broad peaks at ~ 3000 cm -1 of APY gel reflect the characteristic peaks at 3076 cm -1 for PPy and at 2900, 2976, and 3076 for A-gel. Except for this peak broadening around 3000 cm -1, no other significant peak shifts were observed for APY gel compared to A-gel and PPy, suggesting that the gelation and polymerization did not alter the original optical properties of A-gel and PPy. Figure S5. Raman spectroscopy of A-gel, PPy, and APY gel. S6
The electrical conductivity of APY gel was measured using both 4-point probe method and conductivity meter. It has been known that the 4-point probe method measures the sheet resistance of the surface and conductivity meter directly measures the bulk conductivity. In particular, in using conductivity meter, the probe bulb of conductivity meter was surrounded by the gelated APY gel in such a way that the probe bulb was put into the melt APY gel and APY gel was allowed to form the gel on the probe bulb. From these measurements, we confirmed that the surface and bulk conductivities of APY gel were very close for different pyrrole concentrations. The results are given as a table below. Table S1. Comparison of conductivity between 4-point probe method and conductivity meter for the APY gel Pyrrole concentration (mm) 4-point probe (S/cm) Conductivity meter (S/cm) 15 0.22 ± 0.13 0.20 ± 0.12 30 0.24 ± 0.14 0.26 ± 0.15 75 0.52 ± 0.23 0.55 ± 0.26 150 0.63 ± 0.29 0.61 ± 0.28 450 0.69 ± 0.31 0.67 ± 0.32 S7
Gelation of APY gel highly depends on the ph of gel medium because the concentration of proton or hydroxide ion affects the hydrogen bonding of A-gel. We separately tested the gelation of agarose with different acidic and basic environment. As shown in Table S1, the gelation did not occur in most acidic condition (higher than 0.1M HCl) for 1 2 wt. % agarose solution. For basic condition, the gelation only occurred at relatively mild basic condition (less than 0.1 M NaOH) for 1 2 wt. % agarose solution. From these respects, the reversibility of APY gel is significantly influenced by the ph environment during the gelation. Table S2. Gelation of APY gel in acidic and basic environment. S8
S6. Bending resistance of APY gel Figure S6. Photograph of APY gel at the bending angle of a, 0, b, 15, c, 25, d, 30, e, 35, f, 40, g, 50, h, 55, i, 65, j, 75, respectively. S9
S7. Effect of thickness of APY gel on bending resistance Normalized resistance 2.0 1.8 1.6 1.4 1.2 1.0 0.8 Bending, t=0.5mm Relaxing, t=0.5mm Bending, t=1.0mm Relaxing, t=1.0mm Bending, t=2.0mm Relaxing, t=2.0mm 0 10 20 30 40 50 60 70 80 Bending angle ( o ) Figure S7. Normalized resistance as a function of bending and relaxing angle with gel thickness of 0.5 (black circle), 1.0 (blue triangle), and 2.0 mm (red square), respectively. S10
S8. Stretching resistance of APY gel Figure S8. Photograph of APY gel at the stretched ratio of a, 0.0, b, 2.5, c, 5.0, d, 7.5, e, 10.0, f, 12.5, g, 15.0, h, 17.5, i, 20.0, j, 22.5, k, 25.0 % compared to the length of original APY gel, respectively. S11
S9. Absorbance of APY gel Absorbance (a.u.) 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 200 400 600 800 1000 1200 Wavelength (nm) Figure S9. UV-visible absorbance spectrum of APY gel. S12