Accession Number:
ADA281174
Title:
Synthesis of Low Band Gap Zwitterionic and Planar Conjugated Pyrrole-Derived Polymers. Reversible Optical Absorbances From the UV to the Near-IR
Descriptive Note:
Technical rept.
Corporate Author:
SOUTH CAROLINA UNIV COLUMBIA DEPT OF CHEMISTRY AND BIOCHEMISTRY
Personal Author(s):
Report Date:
1994-06-28
Pagination or Media Count:
15.0
Abstract:
Described is the synthesis of a zwitterionic pyrrole-derived polymer. The monomer 1 is formally an azomethine ylide and it was synthesized in 3 steps from pyrrole. 1 was polymerized using copper-bronze in DME. The polymer had a strong optical absorbance at 512 nm in THF and an inter-unit ionic interaction is proposed to explain this large red-shifted band. If aqueous NaOH is added to the THF solution, or a Lewis basic solvent used instead of THFNaOH, then a tremendous bathochromic shift occurs to 881 or 901 nm, respectively. The large shifts are attributed to a dramatic structural change in the polymer induced by hydroxide or Lewis base attack on the iminium unit. This causes a cascade of electron shifts to form a fully conjugated polymer that is fixed into a planar conformation. The planarization process is reversible so that addition of acid or shifting to a weaker Lewis basic solvent causes the polymer to recover its zwitterionic form and its original optical absorption characteristics. Moreover, upon mild reduction of the zwitterionic polymer with PdC and H2 1 atm, some of the extended conjugation is lost but a polymer forms that has an enormous optical absorption maximum range from the near-UV to the near-IR Lambda sub max 886 nm depending on the solvent or hydroxide concentration. Further, a sample of the reduced polymer can be dispersed in plasticized polyvinyl chloride. The flexible polymer composite reversibly changed from dark blue-brown in aqueous hydroxide to bright yellow-orange in aqueous HCl.
Descriptors:
- *OPTICS
- *POLYMERS
- *PLANAR STRUCTURES
- *REVERSIBLE
- *PYRROLES
- *ABSORPTION
- INTERACTIONS
- CARBON
- REDUCTION
- MONOMERS
- POLYVINYL CHLORIDE
- ULTRAVIOLET SPECTRA
- DISTANCE MEASURING EQUIPMENT
- BASES(CHEMISTRY)
- ACIDS
- HYDROXIDES
- PALLADIUM
- BLUE(COLOR)
- SOLVENTS
- BRONZE
- CHLORIDES
- SHIFTING
- COPPER
- ELECTRONS
- HYDROGEN
- RED(COLOR)
- SYNTHESIS
Subject Categories:
- Physical Chemistry
- Polymer Chemistry
- Atomic and Molecular Physics and Spectroscopy
- Optics