POLYTHIOPHENES AND OLIGOTHIOPHENES IN ZEOLITE HOSTS - CONJUGATED NANOMETER-SIZE FILAMENTS

The polymerization of different thiophenes in the channels of molecular sieve zeolite hosts is described. Thiophene, 3-methylthiophene, 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 die 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 die 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 H6Y zeolites (2 and 6 protons per super cage/beta-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.