Conducting and biodegradable polymers; applications

Conducting polymers

Conducting polymers are organic polymers that conduct electricity. They have a conjugated backbone (alternating single and double bonds) with delocalised π electrons. When they are doped (oxidised with I₂ or AsF₅, or reduced with Na), charge carriers are created and the conductivity rises by many orders of magnitude. Examples: polyacetylene, polyaniline, polypyrrole, polythiophene.

Advantages

• Light in weight, flexible and low cost compared with metals.
• Easily processed and moulded into films and fibres.
• Conductivity can be tuned by doping.
• Corrosion resistant.

Biodegradable polymers

Biodegradable polymers are polymers that can be broken down by the action of microorganisms (bacteria, fungi) and enzymes in the environment into CO₂, water and biomass. They usually contain links such as ester or amide groups that enzymes can attack.

Examples: PHBV (poly-β-hydroxybutyrate-co-β-hydroxyvalerate; from 3-hydroxybutanoic and 3-hydroxypentanoic acids), polylactic acid (PLA), polycaprolactone, starch- and cellulose-based plastics, and nylon-2-nylon-6 (glycine + aminocaproic acid). Uses: packaging, carry bags, disposable cutlery, surgical sutures, implants, and controlled drug delivery capsules.

Applications of conducting polymers in engineering

• Rechargeable lightweight batteries and supercapacitors.
• Organic light-emitting diodes (OLEDs) and flexible displays, organic solar cells and transistors.
• Antistatic coatings and EMI shielding for electronic devices.
• Chemical sensors and biosensors, artificial muscles.
• Anti-corrosion paints.