Synthesis and Polymerization of Novel Doubly-Polymerizable Thiophenes and Thiophene
Substituted-Norbornenyl Monomers for Their Use in Photovoltaic Cells
Kareha Agesa, Pete Barnes, and Don Warner, PhD
Department of Chemistry and Biochemistry, Boise State University, Boise, ID 83706
Abstract
Polythiophenes are effective organic semiconductors because they are non-corrosive, easily synthesized, conveniently modified, and have lower manufacturing costs compared to silicon-based solar cells.
Doubly-polymerizable thiophene monomers are preferred to traditional polythiophenes because they avoid synthetic challenges that lead to negative impacts in electrochemical properties. The synthesis of novel
doubly-polymerizable thiophene monomers will lead to a variety of conducting organic polymers. Thus far, a 3-carboxylic-terthiophene monomer has been synthesized, and an esterification has resulted in a
norbornenyl substituted 2,5-dibromothiophene. Polythiophene formation techniques will include more traditional chemical and electrochemical methods, specifically utilizing Grignard Metathesis Method and cyclic
voltammetry. Then, ring–opening metathesis polymerization with a Grubbs ruthenium catalyst will lead to a thiophene substituted poly-norbornylene. These methods will work toward uncovering the reliability of
organic polymers with a thiophene framework in the production and use of photovoltaic cells.
Energy Sources
Targeted Monomers
Fossil Fuels:
•  Are nonrenewable
•  Have potential to harm the
environment
Solar Energy:
•  Being researched as possible
energy alternative
•  Used in everyday items, such as
road signs and calculators
•  Utilizes photovoltaics to harvest
energy from the sun
•  Use silicon as a semiconductor
Conductive Polymers in Solar Cells
Polythiophenes:
•  Are conductive polymers
•  Alternative to silicon
•  Are low cost to manufacture and modify
•  Have a low band gap
•  Show delocalization of backbone electrons
•  Have electrical conductivity
Br
S
S
O
S
Br
O
S
O
O
Characterization of Monomers
Br
3-Thiophenecarboxylic acid
S
S
Br
O
Monomer 1
Monomer 2
S
S
O
O
O
O
O
O
S
O
Br
O
R
O
H
OH
Ø  Spectra obtained: 1H, 13C, HSQC, HMBC, & COSY
R = Fatty acid saturated chain
•  All monomer pathways require 3-Thiophenecarboxylic acid.
•  Norbornenyl-substituted thiophene capable of ROMP allowing for double
polymerization.
•  Monomer 1 polymerized through GRIM.
•  Monomer 3 contains a fatty acid which may contribute to unique packing
properties.
Current Progress
S
O
Br
1. Br2
2. AcOH
S
Br
O
OH
1. SOCl2
2. HO
OH
Br
S
Br
O
1. CH3MgCl
2. Ni(dppp)Cl2
S
O
O
(49%)
1. C16H30SSn
2. Pd(PPh3)4
(67%)
1. SOCl2
2. HO
S
n
O Polymer A
•
•
•
•
1. C16H30SSn
2. Pd(PPh3)4
S
S
•  Explore potential of thiophene framework in solar cells.
•  Prepare novel doubly-polymerizable thiophene monomers
•  Polymerize the monomers using Grignard Metathesis
Method (GRIM) and ring-opening metathesis (ROMP).
•  Characterize the polymers using electrochemical methods
such as cyclic voltammetry (CV) and Ultraviolet-visible
spectroscopy (UV-vis).
1. Br2
2. AcOH
S
O
O
S
S
Br
O
S
1. FeCl3
1. SOCl2
2. HO
Br
O
OH
O
1. SOCl2
2. HO
+
Bu3Sn
S
1. CV
O
n
Polymer B
S
n
O
S
Conclusion/Future Work
S
O
S
R
•  Synthesize and characterize Monomer 3
•  Characterize Polymer A using CV and UV-vis.
•  Synthesize and characterize Polymer B
O
O
Polymer C
O
R
O
Shows proton to carbon correlation
CH2 (geminal) shown in red
CH shown in black
Shows carbons directly attached to proton
S
O
S
O
OH
Research Objectives
Monomer 1 in CDCl3
•  Monomer 2 possibly polymerized by chemical or electrochemical synthesis.
S
Figure 1: Basic polythiophene
H
b
R
Monomer 3
S
S
c
Ha
O
S
*
*
Br
OH
OH
Bu3Sn
S +
Br
S
O
a
O
Br
Monomer 1 in CDCl3
R = Fatty acid saturated chain
•  Polymer A utilized GRIM with the nickel catalyst.
•  Polymer B will be synthesized using CV or Fe3Cl.
•  Monomer 3 will be synthesized through metal-catalyzed cross-coupling,
then polymerization techniques will be attempted.
Acknowledgements
•  This project was supported by REU Site: Materials for
Energy & Sustainability, Boise State University grant
number DMR 1359344.