Cyclization of polyphenylacetylene (PPA) into a high molecular weight polycyclic aromatic derivative

摘要

Polyphenylacetylene (PPA) has been cyclized and polycondensed into a polymeric polycyclic aromatic hydrocarbon (PPAH) or, which is the same, into large and very large polycyclic aromatic hydrocarbons (LPAH/VLPAH) by treatment with Friedel-Crafts catalysts. The most effective catalytic systems in the conversion of PPA to PPAH have been proved to be a melt of AlCl3-NaCl and a mixture of AlCl3-SnCl4. The chemical structure of the resulting PPAH has been confirmed by FT-IR and electronic spectroscopy. Using selected bands from the FT-IR spectra it has been shown that it is possible to calculate the degree of polycondensation achieved in the final PPAH produced. Coal (anthracite) has been used as reference material both in FT-IR studies and in thermal analysis. The resulting PPAH shows a thermal behaviour in thermogravimetric analysis completely comparable to that shown by coal. The chemical structures of the final product PPAH and intermediate products are shown and discussed on the basis of FT-IR spectroscopy. The cis-trans isomerisation of PPA under the action of gaseous HCl has been investigated as the early reaction when PPA is treated with Friedel-Crafts catalysts. Furthermore, the chain isomerism of PPA has been discussed and the optimized geometry of each isomer calculated on the basis of the AM I method. The detailed synthesis of the Rh(l) catalyst and the synthesis of PPA have been included. (C) 2003 Elsevier Science Ltd. All rights reserved. [References: 22]