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Preliminary Study of the Preparation and Properties of Polythiophene/Zeolite Composites

Author: ChangJinYu
Tutor: ChangLiPing
School: Taiyuan University of Technology
Course: Physical and chemical
Keywords: polythiophene CeY sorbent polymerization composite material electrical conductivity
CLC: TB33
Type: Master's thesis
Year: 2013
Downloads: 82
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Abstract

Thiophene is one of the main impurities in coking benzene and is also the main raw material for synthesizing the Pharmaceuticals, dyes, pesticides and new polymer. The utilization of thiophene will generate very high economic value and have broad applicational prospects. Especially the new polymer materials polymerized by thiophene monomer, which possesses the good thermal conductivity, chemical stability and hole-transporting, electrically induced discoloration and good photoelectric conversion, has been widely used in the aspects of mechanical and electrical conductor, the hot areas, nonlinear optics, photoelectric, electromagnetic shielding. At the same time, the organic and inorganic composite produced by the polythiophene and some inorganic matter enriches the original properties and some new features will be arisen through their combination. It is worth mentioning that the synergistic effect between the thiophene and inorganic matter and the nanometer effect make the composite materials possess much better characteristics than the single materials. Based on the research work at the early stage, NaY molecular sieve and its Ce ion-modified sorbent (CeY) with good capacity removing thophene from benzene, thiophene and its homologs (3-ethyl thiophene) monomer were used as raw material, the different series of thiophene/molecular sieve composites were prepared by chemical oxidation polymerization method and were also characterized and tested by XRD, SEM, BET, FTIR, UV-vis and TG-DTG techniques in this paper. The photoelectric features of different composite materials and their differences were analyzed in order to optimize the parparing conditions of composite materials.Firstly, NaY zeolite and modified zeolites CeY was respectively polymized with a certain amount of thiophene monomer by oxidative method to prepare NaPTh and CePTh series samples. The characterization and testing results show that the connection among thiophene rings in two series of composites prepared under the conditions of the chloroform as the solvent and anhydrous FeCl3as oxidant at0℃are mainly in the α-α way. The composite material keeps the crystal structure of molecular sieve, has good absorption in the ultraviolet-visible area and a lower band gap width, but the heat stability is poorer. The conductivity of CePTh series samples are obviously better than that of NaPTh, which should be mainly because the presence of S-Ce bond in CePTh series samples make the main chain structures of polythiophene tend to be more complanation.Secondly, SC series of samples were synthesised with CeY zeolites adsorbed thiophene from pure thiophene solution and monomer thiophenes. The performance of SC series samples was characterized and tested, and it was compared with that of CePTh series samples. Results show that the photoelectric performance of SC samples is similar to pure polythiophene, and significantly lower than that of CePTh samples. This is mainly because that the adsorption of monomer thiophenes in the pore of zeolites leads to most of thiophene polymerize incompletely during the process of preparation. The decrease of a-a bond amount in polythiophene, the reduction of the conjugated degree of main chain, and the weakness of pz ortibal overlap degree of C-C in thiophene should be the main reason of wide bandgap and low conductivity of SC series composite materials.Thirdly, CeY molecular sieve adsorbed thiophene from benzene solution was selected to make thiophene monomer polymerization and the NC series samples were obtained. Their performances were also characterized and tested and are compared with SC series of samples. The results show that the conductivity of NC301sample is much higher than that of polythiophene, the highest value can reach1.00×10-6S/m. But their conductive performance is similar to the SC series samples, which is because that the amount of benzene in NC series samples is very few, and thus their effect on the electrical conductivity of the samples is not obvious.Lastly, a series of composite materials were polymerized through3-methyl thiophene monomer with CeY molecular sieve and3-samples were obtained. Comparison with CePTh samples, the conductivity of3-samples is apparently superior to that of CePTh samples. Of which the electrical conductivity of3-301samples is much higher than polythiophene and has the highest value of 3.20×10-6S/m. A possible reason is that methyl introduced in NO.3bond position has a stronger electron-withdrawing inductive effect and weaker electronic conjugation effect than hydrogen atoms of thiophene ring. Methyl’s high electronic effect directly leads to better conjugation degree of main chain of polythiophene in the3-samples and the more complanate structure and thus the best conductivity.

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