William A. Little (Stanford) and excitonic high temp superconductors,
Phys. Rev. A 134 1416 (1964)
Phys. Rev. B 13 4766 (1976)
Given: The BCS model for coupling fermionic opposite momentum conduction band electrons into bosonic Cooper pairs, then Bose condensation into superconductivity. Classic BCS supercons impose electron couplng by lattice deformation. Atomic nuclei are massive and their displacements are only weakly coupled to electron movement.
Replace phonons (quantized lattice vibriatons characterized by Debye temperature) with excitons (quantized electronic excitations) possessing characteristic energies around 2 eV or 23,000 K. Exciton-mediated electron pairing suggests superconductor critical temperatures exceeding 300 K even under the weakest coupling conditions - a robust, processable room temperature organic superconductor.
Little?s structure was polyacetylene bearing polarizable chromophore side groups. Polyacetylene (doped) would be a normal metal with a single mobile electron per C-H molecular unit. Electrons on separate units BCS couple by interacting with side groups? (C-H into C-R) polarizability (excitons from electron slosh) rather than lattice vibrations (phonons from nucleus slosh).
The 1960s proposal was safely beyond synthesis. There was no way to construct a 100% derivatized 100% conjugated polymer backbone. Chromophores could be polycyclic aromatic hydrocarbons or, better, laser dyes; anthraquinone dyes, annelated vat dyes, indanthrene dyes... transition metal complex, Kreutz-Taube ion... A repeated chromophore along the chain would beget a high temp supercon. A chromophore redox gradient would be a supercon diode. A Y-junction would be a supercon transistor. Other molecular devices (e.g., quantum wells) suggest themselves. Pendant group-mediated solubility is not unreasonable.
Such syntheses are now trivially achievable. R is the chromophore. The entirely reasonable monomer is
H2C=C(R)-C(R)=CH2
Grubbs' olefin metathesis extrudes H2C=CH2 gas and Little's proposal is suddenly resident in Pyrex to high molecular weight. Monomer and polymer stereochemistries are implicit. Olefin metathesis is extremely tolerant of unrelated chemical functionality. R may be further elaborated after synthesis. Hydrophobic stacking or hydrogen bonding of chosen chromophores (perhaps plus adjunct small molecules) may access spontaneously ordered 2-D and 3-D lattices.
It is a nice undergraduate independent study project.
