Conjugated Organic Materials

1
Conjugated Organic Materials
Nobel Prize 2000 Shirakawa, Heeger, MacDiarmid

• Applications
• Batteries
• Antistatic Electrochromic Coatings
• Plastic Electronics
• Sensors, etc

Konarka
Sony
2
Conductivity in Polymers

• Insulating Polymers / Semiconductors / Synthetic
  Metals
• Electrical conductivity / Ionic conductivity

Metals
Silver Copper Aluminum
102 to 1010 S /cm
Graphite Polyacetylene Poly(p-phenylene
vinylene) Silicon (10-4)
Aqueous salt solutions (ca. 1)
Doping
Semiconductors
10-5 to 102 S /cm
PEO / LiOTf (10-8)
Glass Polyethylene Polystyrene
Insulators
10-15 to 10-5 S /cm
3
Band Theory
Medium-sized molecule
Large sized molecule
Diatomic molecule
Separate atoms
Antibonding orbital
CB
Band gap
VB
Bonding orbital
Effect on Optical Properties and Ability to
Generate Charge Carriers (Doping)
4
Band Gaps in Common Conjugated Polymers
Conducting Polymer Band Gap
trans-Polyacetylene (PAc) 1.4 eV
Polythiophene (PTh) 2.1 eV
Poly(p-phenylene vinylene) (PPV) 2.5 eV
Intrinsically non-conductive polymers !
5
Synthetic Aspects

• Oxidative Polymerization (electrochemical /
  chemical)
• Example Polythiophenes, polypyrrole, polyaniline
• Polymerization through organo-
• metallic coupling reactions
• Example Polythiophenes, polypyrrole, PPV
• Polymer Modification
• Example PPV derivatives

Stille Coupling Suzuki-Miyaura Coupling etc
6
GRIM Process for the Synthesis of Regioregular
Poly(3-alkylthiophene)s
An Example of a Living Condensation
Polymerization Process
R group ends up at polymer chain end

• First Step Conversion of dibromothiophene to
  Grignard Species
• Second Step Catalytic process (Kumada coupling)
• Third Step In our case hydrolysis also
  possible to react with a second Grignard species

7
GRIM Mechanism
8
Applications

• Coatings Polypyrrole, Polythiophenes
• Antistatic coatings, fibers polypyrrole, PEDOT
  (BaytronTM)
• Anticorrosive coatings polypyrrole
• Electrochromic Windows polythiophenes
• Electronic Devices PPV, Polythiophenes
• Polymer Light Emitting Diodes (PLEDs)
• Field-Effect Transistors
• Photovoltaics (combination with fullerenes)
• Sensors functionalized PPV, polythiophene
  derivatives, polyaniline

Cathode
MgAg
e -
Conjugated Polymer
h
Anode
ITO
Transparent Cover
hn
Swager et al., Chem Rev. 2000, 2537.