ABSTRACT:Coumarin-containing polyamides from 6-{[3-(chloroformyl)phenyl]ethynyl}coumarin-3-carboxylic acid chloride were prepared and characterized for the first time. They were soluble in common organic solvents such as Nmethylpyrrolidone (NMP) and dimethyl sulfoxide (DMSO) and gave transparent and tough films on casting. In the presence of excess diamine, the polymers underwent chemical transformation at room temperature, producing polyazomethynes, as confirmed by the corresponding model reactions, and a possible reaction mechanism is proposed for this transformation. The coumarin containing polyamides showed emission and excitation maxima peaking at 464 and 398 nm, respectively, in solution and exhibited I 0% weight loss above 400°C.KEY WORDS Coumarin / Polyamides / Photoluminescence / Coumarines (1,2-benzopyrones) and a class ofheterocycles known for fluorescent properties. They are widely used as laser dyes 1 ' 2 due to high photostability and quantum yield of photoluminescence. The chemical modification of coumarines makes it possible to vary emission wavelength continuously throughout visible spectrum. 3 Coumarines were also found to be electroluminescent. Thus, a dispersion of coumarin 6 in polymethylmethacrylate showed electroluminescence 4 peaking at 554 nm.
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Coumarin 6Although many papers have been published on the synthesis and characterization of coumarines and various reviews are available 3 • 5 very little attention has been paid to the incorporation of coumarines into polymers and only two papers have been published on this topic. The radical copolymerization of coumarin with styrene was studied by Yun. 6 Polyesters containing a coumarin dimer were obtained by the photopolymerization of 7,7'-coumarinylpolymethylene dicarbonates. 7 In these cases, the double bond of coumarin participates in the polymerization giving polymers containing derivatives of 3,4-dihydrocoumarin which do not have interesting optical properties because of the disturbing of the conjugation. On the other hand, polymeric materials containing emitter units have advantage over low molecular weight analogies, especially in making of electroluminescence devices; because of the absence of phase separation, and the possibilities of preparation of thin films of any desirable dimension with high optical quality by simple casting.t To whom correspondence should be addressed.We published recently a series of studies on the synthesis of polymers containing discrete conjugated units of fluorescein, 8 • 9 diethynylantracene, 10 vinylphenylantracene, 11 and arylenevinylideneethynylene. 12 All these polymers gave films with good optical quality on casting. Fluorescein-containing polymers exhibited nonlinear optical susceptibility of the third order of 3 x 10-10 esu, while anthracene-containing polymers showed electroluminescence at voltage as low as 6 V.This work describes the synthesis and characterization of polyamides containing 3,6-disubstituted coumarine units for the first time.
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Materials1,2-Dichlorobenzene was purifie...