CONJUGATED AROMATIC POLY(AZOMETHINES) .1. CHARACTERIZATION OF STRUCTURE, ELECTRONIC-SPECTRA, AND PROCESSING OF THIN-FILMS FROM SOLUBLE COMPLEXES

被引:209
作者
YANG, CJ
JENEKHE, SA
机构
[1] UNIV ROCHESTER,CTR PHOTOINDUCED CHARGE TRANSFER,ROCHESTER,NY 14627
[2] UNIV ROCHESTER,DEPT CHEM ENGN,ROCHESTER,NY 14627
关键词
D O I
10.1021/cm00017a025
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
A series of conjugated aromatic poly(azomethines), poly(1,4-phenylenemethylidynenitrilo-1,4-phenylenenitrilomethylidyne) (PPI), poly(2-methyl-1,4-phenylenemethylidynenitrilo-1,4-phenylenenitrilomethylidyne) (PMPI), poly(1,4-phenylenemethylidynenitrilo-2,5-dimethoxy-1,4-phenylenenenitrilo-methylidyne) (PMOPI), poly(1,4-phenylenemethylidynenitrilo-2,5-dihydroxy-1,4-phenylenenitrilo-methylidyne) (PHOPI), and copolymer PPI/PMPI, have been prepared and solubilized in organic solvents by reversible complexation with either gallium chloride or di-m-cresyl phosphate (DCP) and characterized. The molecular structure of the aromatic polyazomethines was characterized by H-1 NMR spectra of the polymers in GaCl3/deuterated nitromethane. The conjugated aromatic poly(azomethines) were processed into optical-quality thin films from their soluble complexes in organic solvents and characterized. The solid-state electronic absorption spectra showed that the lambda-max for pi-pi* transition varies from 405 nm for PPI to 497 nm for PHOPI. The corresponding solid-state bandgap was in the range 2.07-2.50 eV. The relatively low bandgap of PHOPI (2.07 eV) compared to PMOPI (2.34 eV) and PPI (2.50 eV) is due to its intramolecular hydrogen-bonding-mediated coplanar structure. Intramolecular hydrogen bonding in PHOPI was further evidenced by FTIR spectra and the results of solubility and complexation studies. The solid-state electronic absorption spectra of complexes of these conjugated aromatic poly(azomethines) were found to exhibit greater electronic delocalization and smaller bandgaps (1.85-2.15 eV) than the pure polymers. Origin of this remarkable red shift of electronic spectra was attributed to complexation-induced change in polymer conformation. The preparation of soluble complexes of conjugated aromatic poly(azomethines) and their processing to optical-quality thin films has now opened up investigation of the solid-state properties of this class of liquid-crystalline conjugated polymers and high-temperature fiber-forming materials.
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页码:878 / 887
页数:10
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