Conducting polymer wires in mesopore hosts

Nanometer-size conducting structures are of great interest in view of fundamental issues and potential applications. We explore the inclusion chemistry of conjugated polymers and graphite-like materials as a means to create such structures. Novel mesoporous materials with pore diameters in the 3 nm range (MCM-41) are used as hosts. Monomer molecules are introduced via vapor or solution transfer and polymerized either by included or external reagents. The properties of the conjugated systems are studied while encapsulated or after dissolution of the host. In the case of polyaniline formed on oxidation of aniline with persulfate, microwave absorption shows the presence of conducting filaments in the host channels. The above systems are compared with graphite-type material encapsulated in MCM-41 by first forming a precursor polymer such as polyacrylonitrile that is pyrolyzed at 500-800°C. These polymer chains are the first nanometer-size conducting filaments stabilized in a well-defined channel host

Encapsulation of polyaniline in zeolite Y and mordenite

Synthetic strategies to encapsulate polyaniline in the crystalline channel system of faujasite (three-dimensional) and mordenite (one-dimensional) have been explored. The adsorption of anilinium precursor into the zeolite host and its successful oxidation to polyaniline have been studied utilizing FTIR, Fourier Transform Raman, and electronic spectroscopies. The dimensionality of the host channel system and the concentratio

Polythiophenes and oligothiophenes in zeolite hosts

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

Intrazeolite synthesis of polythiophene chains

Adsorption of thiophene and 3-methylthiophene into the channel system of transition metal-containing zeolites Y and mordenite results in oxidative polymerization to give encapsulated chains of polythiophene and poly(3-methylthiophene)

Intrazeolite assembly and pyrolysis of polyacrylonitrile

Radical polymerization of acrylonitrile within the pores of zeolites Y and mordenite produces intrazeolite polyacrylonitrile that can be pyrolysed to form conducting carbon filaments

Synthesis of oligo- and polythiophenes in zeolite hosts

Oligomers and polymers of thiophene derivatives were synthesized in the channels of zeolite Y and mordenite. Intrazeolite oxidation of monomers such as thiophene , 3- methylthiophene , and bithiophene by Fe(lll) or Cu(ll) ions results in formation of insoluble polymers that have spectroscopic properties similar to the corresponding bulk polymers. The zeolites containing the polymers are nonconducting, but when extracted from the host, the polymers show d.c. conductivities typical for t he bulk materials. Oligothiophene species with welldefined electronic transitions could be produced in acidic zeolite Y