Conducting Polymers: Introduction and Conductivity

The band gap.

If the band gap is near zero or there is overlap, it allows for greater conductivity.

The band gap decreases and can become nearly zero due to conjugation.

<p>They have good electrical conductivity, the ability to store charge, and can absorb visible radiation.</p> Signup and view all the answers

<p>Conducting polymers are generally not thermoformable.</p> Signup and view all the answers

<p>Conjugation lowers the energy required for electronic transitions.</p> Signup and view all the answers

<p>The π - Molecular Orbital Diagram illustrates the energy levels and bonding interactions, affecting their conductivity.</p> Signup and view all the answers

<p>Electrical properties can be fine-tuned through organic synthesis and dispersion techniques.</p> Signup and view all the answers

<p>Conducting polymers are organic polymers that exhibit unique electrical and optical properties, unlike traditional polymers that are insulators.</p> Signup and view all the answers

<p>Ohm's law states that resistance is proportional to the length of a sample and inversely proportional to its cross-section, providing a foundational understanding of how materials conduct electricity.</p> Signup and view all the answers

<p>Resistivity (ρ) is the measure of a material's resistance, while conductivity (σ) is its inverse, expressed as σ = ρ⁻¹.</p> Signup and view all the answers

<p>For metallic materials, conductivity typically increases with decreasing temperature, while for semiconductors, conductivity usually decreases with lowering temperature.</p> Signup and view all the answers

<p>The presence of highly delocalized, polarized, and electron-dense π bonds enables electrical conductivity in conjugated carbon chains.</p> Signup and view all the answers

<p>Examples include linear polyene chains, which deviate from Ohm's law and demonstrate unique electrical properties.</p> Signup and view all the answers

<p>Examples include polyacetylene (PA) and polyaniline (PANI), which are significant for their applications in electronics due to their conductivity.</p> Signup and view all the answers

<p>Doping involves oxidation, which removes some delocalized electrons, creating a partially vacant electronic band that allows for high mobility of the remaining electrons.</p> Signup and view all the answers

<p>The number density of charge carriers (electrons) and their mobility are crucial for the conductivity of conjugated polymers.</p> Signup and view all the answers

<p>Extrinsically conducting polymers achieve conductivity through the addition of external ingredients, such as conducting elements or other conducting polymers.</p> Signup and view all the answers

<p>Materials with high symmetry, like diamond, tend to be isotropic and are often insulators, while anisotropic materials, like graphite, can be highly conductive when doped.</p> Signup and view all the answers

<p>The Nobel Prize was awarded for the discovery and development of conductive polymers by Alan J. Heeger, Alan G. MacDiarmid, and Hideki Shirakawa.</p> Signup and view all the answers

<p>The percolation threshold is the minimum concentration of a conducting filler required for the polymer to exhibit electrical conductivity.</p> Signup and view all the answers

<p>Conducting elements filled polymers incorporate external conductive materials, while blended conducting polymers combine a conventional polymer with a conducting polymer.</p> Signup and view all the answers

<p>The pz orbitals on sp2 hybridized carbon centers overlap to form a delocalized set of orbitals, which allows electrons to move freely and contribute to conductivity.</p> Signup and view all the answers

<p>Intrinsically conducting polymers have a backbone of sp2 hybridized carbons with delocalized π bonds, whereas extrinsically conducting polymers require external additives for conductivity.</p> Signup and view all the answers

<p>The main method for synthesizing polyacetylene is through metathesis using the Grubbs route.</p> Signup and view all the answers

<p>Substitutions at the 3- and 4-positions improve the solubility of polythiophenes.</p> Signup and view all the answers

<p>When polythiophenes are oxidized, they become conductive due to the delocalization of electrons along the polymer backbone.</p> Signup and view all the answers

<p>Dramatic color shifts in polythiophenes can be caused by changes in solvent, temperature, potential, and binding to other molecules.</p> Signup and view all the answers

<p>The chemical oxidation method involves oxidative polymerization of thiophenes using ferric chloride at room temperature in solvents like chloroform or CCl4.</p> Signup and view all the answers

<p>The quality of the resulting polythiophene polymer depends on the electrode material used in the electrochemical polymerization.</p> Signup and view all the answers

<p>Polythiophenes can be used in field-effect transistors and electroluminescent devices.</p> Signup and view all the answers

<p>A major disadvantage is that it can produce polymers with undesirable alpha-beta linkages and variable regioregularity.</p> Signup and view all the answers

<p>The three methods are chemical, electrochemical, and photoelectrochemical.</p> Signup and view all the answers

<p>The chemical method requires high control because the reaction is very exothermic, releasing a large amount of energy.</p> Signup and view all the answers

<p>Most polymers have covalent bonds that are directional, which locks electrons, preventing their drift and resulting in poor conductivity.</p> Signup and view all the answers

<p>Doping introduces charges into the polymer, allowing movement of charge through resonance in chains with alternating double and single bonds.</p> Signup and view all the answers

<p>The alternating double and single bonds in polythiophene allow for resonance-driven charge movement.</p> Signup and view all the answers

<p>As doping levels increase, more charges are formed in the polymer, resulting in greater conductivity.</p> Signup and view all the answers

<p>Poly(3-hexylthiophene), or P3HT, is a polythiophene with the chemical formula (C10H14S)n, widely used in organic electronics.</p> Signup and view all the answers

<p>The electrochemical method's limitation is the shape of the polymer, which mimics the electrode, necessitating further processing.</p> Signup and view all the answers

<p>It creates a positive charge through oxidation, allowing for electrical conduction.</p> Signup and view all the answers

<p>P-doping removes electrons creating positive charges, while n-doping adds electrons creating negative charges within the polymer.</p> Signup and view all the answers

<p>The polaron, a radical cation formed by electron removal, allows for the delocalization of positive charges along the polymer chain, facilitating conductivity.</p> Signup and view all the answers

<p>Synthesis below −78 °C favors the cis-form, while above 150 °C favors the trans-form of polyacetylene.</p> Signup and view all the answers

<p>N-doping introduces electrons into the conjugated π-bonds, creating negative charge carriers that enhance conductivity.</p> Signup and view all the answers

<p>Common Lewis acids include FeCl3 and AlCl3.</p> Signup and view all the answers

<p>The Ziegler–Natta catalyst method is commonly used for this synthesis.</p> Signup and view all the answers

<p>The bipolaron is formed by the loss of another electron from the polaron, leading to enhanced charge delocalization and conduction.</p> Signup and view all the answers