Supporting Information
Synthesis and Photophysical Properties of Soluble
Low-bandgap Thienothiophene Polymers with
Various Alkyl Side Chain Lengths
Woo Jin Bae†, Christopher Scilla†, Volodimyr V. Duzhko†, Won Ho Jo‡, E. Bryan Coughlin†*
†
Department of Polymer Science and Engineering, University of Massachusetts Amherst, Conte Center
for Polymer Research, 120 Governor Drive, Amherst, Massachusetts 01003
‡
Department of Materials Science and Engineering, Seoul National University, Seoul 151-742, Republic
of Korea
§
Energy Frontier Research Center PHaSE, University of Massachusetts, Amherst, MA 01003, USA
Coughlin@mail.pse.umass.edu
Phone: 413-577-1616/ Fax: 413-545-0082
S-1
Supporting Information
We should note here that after polymerization, the ring protons at  = 6.61 ppm in the 1H NMR
spectra of Ttx monomers look shifted and overlapped with CHCl3 peaks. Although it was previously
reported that the proton peak of thienothiophene ring is shifted to 6.64 ppm upon polymerization,18 we
were not able to observe any proton peak around 6.64 ppm. For the clear evidence of thiophene ring
protons,
1
H NMR spectra of PTtx was obtained in CD2Cl2 to prevent the proton peaks in
thienothiophene ring from overlapping with the solvent peak. As shown in Figure 1S(a) and 1S(b), the
proton peak around 7.0 ppm was observed without any discernible peak at around 6.64 ppm in both
polymers (PTt8 and PTt13).
More crucial evidence is the 1H NMR spectrum of low molecular weight PTt13 (Mn = 1.2 K, Ð =
1.4) (Figure 1S(c)), which exhibits two distinct proton peaks in the range of 6.9 to 7.4 ppm. As peak
broadening in high molecular weight polymers often make it difficult to interpret real resonance peak
position, we synthesized low molecular weight PTt13 to investigate the ring proton shift. The previous
report18 didn’t contain any 1H NMR spectrum in their paper or in the supporting information. Otherwise,
we found 1H NMR spectrum of poly(2-decylthieno[3,4-b]thiophene) from their thesis (in page 94,
101),23 which does not show any discernible peak around 6.64 ppm and look very similar to 1H NMR
spectra of PTtx synthesized in our hands.
Table 1S. Nomenclature of BrThx and Ttx
BrThx (x=5,6,7,8,13)
Ttx (x=5,6,7,8,13)
CH2 -CH3
x-1
S
S
S
Br
S-2
CH2 -CH3
x-1
Figure 1S. 1H NMR spectra of (a) PTt8 (Mn = 5.4 K, Ð = 1.5), (b) PTt13 (Mn = 3.5 K, Ð = 1.5) and (c)
PTt13 (Mn = 1.2 K, Ð = 1.4)
S-3
Figure 2S. 1H and
(ppm)
13
C peak assignments for (a) Tt8 and (b) Br-Tt8-Br reported in parts per million
(a)
(b)
7.14
Br
H
95.19
110. 10
S
147.66
110. 30
H
7.14
H
S
6.61
95.93
113.28
Br
153.09
138.84
S
147.02
6.48
113.50
139.62
155.04
S
R
H
R
Figure 3S. 1H NMR spectra of (a) BrTh5, (b) BrTh6, (c) BrTh7, (d) BrTh8 and (e) BrTh13.
S-4
S-5
Figure 4S. 1H NMR spectra of (a) Tt5, (b) Tt6, (c) Tt7, (d) Tt8 and (e) Tt13.
S-6
S-7
Figure 5S. 1H NMR spectra of (a) Br-Tt5-Br, (b) Br-Tt6-Br, (c) Br-Tt7-Br, (d) Br-Tt8-Br and (e) BrTt13-Br.
S-8
S-9
Figure 6S. 1H NMR spectra of (a) PTt5, (b) PT6t, (c) PTt7, (d) PTt8 and (e) PTt13.
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Figure 7S. FTIR spectra of (a) PTtx-O and (b) PTtx-G
(a)
(b)
PTt5-G
Transmittance (A.U.)
Transmittance (A.U.)
PTt5-O
PTt6-O
PTt7-O
PTt8-O
PTt13-O
3000
2500
2000
1500
1000
500
PTt6-G
PTt7-G
PTt8-G
3000
-1
1500
wavenumber (cm-1)
Wavenumber (cm )
Table 2S. FTIR peak assignments for PTtx
cm-1
Assignments
2955
CH3 asymmetry stretching
2923, 2852
CH2 in and out of phase mode
1553, 1480
C=C ring-stretching (Ttx)
1450
CH2 bending
815
C-H out of phase bending (Ttx)
734
C-S-C stretching
S-11
1000
500
Figure 8S. GPC traces of PTtx’s synthesized by (a) oxidative polymerization (CHCl3, PS standard) and
(b) GRIM polymerization (THF, PS dtandard)
(b)
(a)
PTt13
PTt8
PTt7
PTt6
PTt5
Intensity (A.U.)
Intensity (A.U.)
PTt8
PTt7
PTt6
PTt5
5
10
15
20
25
16
Elution Time (min)
18
20
22
24
Elution TIme (min)
S-12
26
28
Figure 9S.
1
H NMR spectra of 4,6-dibromo-2-alkyl-thieno[3,4-b]thiophene (Br-Ttx-Br) after
magnesium halogen exchange with isopropylmagnesium chloride (iPr-MgCl)
S-13
Figure 10S. Dynamic light scattering of PTtx-O(1 mg/5 ml of CHCl3). Measurement was done after
filtering through 0.25 m syringe filter.
25
PTt5-O
PTt6-O
PTt8-O
PTt13-O
20
Volume (%)
15
10
5
0
1
10
100
1000
Diameter (nm)
Figure 11S. TGA thermogram of (a) PTtx-O and (b) PTtx-G
(a)
(b)
120
120
PTt5-O
PTt6-O
PTt7-O
PTt8-O
PTt13-O
100
100
Residue (wt%)
Residue (wt%)
80
60
40
PTt5-G
PTt6-G
PTt7-G
PTt8-G
80
60
40
20
20
0
0
200
400
600
0
800
0
o
200
400
600
o
Temperature ( C)
Temperature ( C)
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800
Figure 12S. 1st derivative TGA thermogram of (a) PTtx-O and (b) PTtx-G
(b)
(a)
0.8
5
PTt5-O
PTt6-O
PTt7-O
PTt8-O
PTt13-O
4
Derivative Weight (A.U.)
Derivative Weight (A.U.)
0.6
PTt5-G
PTt6-G
PTt7-G
PTt8-G
0.4
0.2
0.0
3
2
1
0
-0.2
-1
0
200
400
600
800
200
Temperature (oC)
400
600
800
Temperature (oC)
Table 3S. UPS and CV results of P3HT as an internal reference
UPS
Sample
P3HTc
a
E1 (eV)
E2 (eV)
14.47
-1.8
(E1-21.2 eV)a
(eV)
-6.73
CV
HOMO
(eV)
LUMO
(eV)
HOMO
(eV)
-4.93
-3.02
-5.13
Ekin, csynthesized by GRIM polymerization method, Mn = 20 K, Ð = 1.13
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Bandgap
(eV)
2.11