Enzel, Patricia; Bein, Thomas
Polythiophenes and oligothiophenes in zeolite hosts. Conjugated nanometer size filaments.
In: Synthetic Metals, Vol. 55, No. 2-3: pp. 1238-1245
The polymerization of different thiophenes in the channels of molecular sieve zeolite hosts
is described. Thiophene, 3-methyIthiophene, 2,2'-bithiophene, and terthiophene were introduced
into dehydrated proton-, Cu(II)- or Fe(III)-containing zeolites (NaY and Na-mordenite) from
organic solvents or vapor-phase. In the large-pore hosts, green-black products are formed
from the monomers within several minutes. Spectroscopic characterization (IR, UV-NIR)
confirms the formation of oxidized polymer chains in the zeolite channels. UV-Near IR reflectance
spectra of the zeolite/polythiophene samples exhibit a broad absorption from 500 to about 2500 nm
as the bulk and not the resolved spectra of short oligomers, thus fairly long polymer chains are
formed in the zeolites. Conducting polymers can be recovered after dissolution of the zeolite host
in HF. 2, 2'-bithiophene and a-terthiophene in acidic H2Y and U^Y zeolites (2 and 6 protons per
super cage/ß-cage) yield yellow-green and purple products, respectively. UV-NIR reflectance data
indicate that the acidic zeolite hosts oxidize the thiophene oligomers to yield stable radical cations
and dications in their channel systems.