Supplementary Information

Elastic, Conductive, Polymeric Hydrogels and Sponges

Yun Lu†1, Weina He†2, Tai Cao1, Haitao Guo1, Yongyi Zhang2, Qingwen Li2, Ziqiang

Shao1, Yulin Cui3, Xuetong Zhang1,2

1School of Materials Science & Engineering, Beijing Institute of Technology, Beijing

100081, P. R. China2Suzhou Institute of Nano-tech & Nano-bionics, Chinese Academy of Sciences,

Suzhou, 215123, P. R.China3College of Chemistry, Chemical Engineering & Material science, Soochow

University, Suzhou, 215123, P. R. China

[†] These authors contribute equally to this work

Email: zhangxtchina@yahoo.com

Dated: April, 2014

Figures

Figure SI1 Photographs of various conducting polymer hydrogels under compression, from

all of which elasticity cannot be observed: (a) polyaniline (PAni) hydrogel reported

elsewhere1; (b) PEDOT-S hydrogel reported in our previous study2 (c) polypyrrole nanotube

hydrogel reported elsewhere3.

Figure SI2 FT-IR spectra of PPy oxidized by equimolar amount of Fe(NO3)3 without (a) and

with (b) aging process. The bands at 1540 cm-1 corresponds to the pyrrole ring vibration. The

bands at 1450 cm-1 correspond to the =CH in-plane vibration and the peaks at 893 cm -1 and

783 cm-1 are due to the =CH out-of-plane vibration. The stretching vibration of C-N bonds

shows a band at 1300 cm-1 and the band at 1170 cm-1 corresponds to the C-C stretching. A

very intense band at 1040 cm-1 is assigned to in-plane deformation of C-H and N-H bonds of

pyrrole ring4. In comparison with the FT-IR spectra of PPy before and after aging process,

there are no obvious changes in band positions. It can be inferred that the aging process only

concerns about hydrogel network morphological changes resulting in the slow oxidization

step instead of the rearrangement of molecular chains. The absence of absorbing bands at

1210 cm-1 and 800 cm-1 has indicated the low doping level caused by the deficient oxidation.

2400 2000 1600 1200 800 400

(b)

Inte

nsity

(a.u

.)

Wavenumber ( cm-1)

1540

1450

1300

11701040

893783

1540

14501300

11701040

893783

(a)

Figure SI3 Raman spectra of PPy oxidized by equimolar amount of Fe(NO3)3 before (a) and

after (b) aging process. The bands at 930 and 1046 cm -1 are due to C-H out-of-plane and in-

plane deformation, respectively. The bands at 1244 cm-1 corresponds to N-H in-plane

deformation. The pyrrole ring stretching shows bands at 1315 and 1407 cm -1. The band at

1588 cm-1 shows the low doping level of PPy chains5. There are no obvious changes in Raman

spectra before and after aging of the PPy hydrogel oxidized by equimolar amount of

Fe(NO3)3.

500 750 1000 1250 1500 1750 2000

(b)Inte

nsity

(a.u

.)

Wavenumber ( cm-1)

(a)

930

1046

12441315

1407 1588

Compress Release(b)

Compress Release(c)

(a) Compress Release

Figure SI4 Photographs of polypyrrole hydrogels, synthesized by deficient Fe(NO3)3 without

aging (a), sufficient Fe(NO3)3 without aging (b) and deficient FeCl3 with aging for 30 days at

room temperature (c) respectively, under compression and release process.

Figure SI5 Dynamic rheology behaviors of PPy hydrogel during aging procedure. The curves

of storage modulus (Eʹ) and loss modulus (Eʺ) vs. angular frequency (a) and the curve of Eʹ at

=10 rad/s vs. aging time (b).

1 10 100102

103

104

105

106

Aging for 1 day: E' E" 5 days: E' E" 10 days: E' E'' 15 days: E' E'' 20 days: E' E'' 30 days: E' E"

E' ()

, E"(

) (P

a)

( rad s-1)

(a)

0 5 10 15 20 25 300

1x104

2x104

3x104

4x104

E'(

=10

rad

s-1)

(Pa)

Aging times (days)

(b)

Figure SI6 SEM images of PPy sponge without (a, b) and with (c, d) compression..

Figure SI7 The changes of electrical resistance for the PPy sponge sensor during compression

and release circles. The electrical response of the PPy sponge to the external stimulations

0 25 50 75 100 125 150 175-1

0

1

2

3

4

R/R

0 (%

)

Time (s)

Compression strain 50 %

exhibits good stability.

References

1. Pan, L. et al. Hierarchical nanostructured conducting polymer hydrogel with high electrochemical activity. PNAS 109, 9287-9292 (2012).

2. Du, R., Xu, Y., Luo, Y., Zhang, X. & Zhang, J. Synthesis of conducting polymer hydrogels with 2D building blocks and their potential-dependent gel-sol transitions. Chem. Commun. 47, 6287-6289 (2011).

3. Wei, D. et al. Controlled growth of polypyrrole hydrogels. Soft Matter 9, 2832-2836 (2013).

4. Zhang, X. et al. Single-walled carbon nanotube-based coaxial nanowires: sythesis, characterization, and electrical properties. J. Phys. Chem. B. 109, 1101-1107 (2005).

5. Liu, Y.-C., Hwang, B.-J., Jian, W.-J. & Santhanam, R. In situ cyclic voltammetry-surface-enhanced Raman spectroscopy: studies on the doping–undoping of polypyrrole film. Thin Solid Films 374, 85-91 (2000).