Crosslinking of polyaniline with aryl azides and the photolysis of vinyl azides and azidopropanones
We used o-azidoaniline, 4, 4'-diazidobiphenyl and 4, 4'-diazidooctafluorobiphenyl to crosslink polyaniline. o-Azidoaniline was copolymerized with aniline to form poly(aniline-co-azidoaniline), which was crosslinked via thermal activation of the azido groups. . Thermal analysis of the copolymer, poly(aniline-co-azidoaniline) indicated that their thermal stability improved upon crosslinking . 4,4'-diazidobiphenyl and 4,4'-diazidooctafluorobiphenyl were used as post polymerization crosslinking agents. The thermal crosslinking of the polyaniline with these aryl azides was demonstrated with the help of Differential Scanning Calorimetry, Thermogravimetric Analysis and FT-IR spectroscopy. Crosslinked polyaniline films showed a better thermal stability than the plain polyaniline films. The electrical conductivities of the crosslinked polyaniline films were measured with a 4 point probe, which demonstrated that the conductivities were conserved upon crosslinking. The mechanical properties of the crosslinked polyaniline films are tested by Dynamic Mechanical Analysis and the crosslinked polyaniline films show an improvement in tensile strength. Mechanistic studies of these biphenyl azides revealed that the mechanism of crosslinking depends on the environment. Photolysis of 4-azido, 3-methyl, 1-phenyl-buten-1-one in argon matrices yields formation of benzoyl and allyl imine radicals. Computational studies of stationary points on the triplet energy surface of 4-azido, 3-methyl, 1-phenyl-buten-1-one indicate the formation of above radicals goes through a hot triplet vinyl nitrene intermediate. TD-DFT calculations support the first excited triplet ketone and the second excited triplet ketone in 3-azido-1,3-diphenyl-propan-1-one 3-azido-2, 2-dimethyl-1, 3-diphenyl-propan-1-one are almost degenerate. Calculations support that the triplet excited state with an (n,pi*) configuration will cleave to form azido radical and the corresponding benzyl radical whereas the triplet ketone with a (pi,pi*) configuration results in formation of triplet alkyl nitrene intermediates.
School:University of Cincinnati
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:polyaniline aryl azides substituted poly aniline co azidoaniline biphenyl dynamic mechanical analysis dsc tga vinyl hydrazoic acid azidopropanones matrix isolation gaussian
Date of Publication:01/01/2008