INTRINSIC DICHROISM OF DISPERSE DYES

The visible dichroism due to the dispersed dye molecules is related to amorphous orientation of polymer. The dichroic values, D=(K_??_-K⊥)/(K_??_-2K⊥), of polymer films dyed with disperse dyes, C. I. Disperse Yellow 7 (Y-7) and C. I. Disperse Red 17 (R-17), were measured in order to obtain the intrinsic dichroism of dye molecule and to clarify the states of dye in polymer.Polymer films used were poly (ethylene terephthalate), 6 nylon, cellulose triacetate, cellulose diacetate and polypropylene. Especially, poly (ethylene terephthalate) film was stretched and dyed with various dyes. The intrinsic dichroism, D0, of each dye was estimated by comparing with D0 of Y-7.The results obtained are as follows:(1) The disperse dye possessing a longer and slender form shows higher dichroism.(2) The intrinsic dichroism, D0, of Y-7 on poly (ethylene terephthalate) and polypropylene is1. On 6 nylon, cellulose triacetate and cellnlose diacetate the D0 estimated under some assumptions is also in unity.(3) In the dichroism no fundamental difference is observed in the dyeing modes of R-17 on poly (ethylene terephthalate), 6 nylon, cellulose triacetate and cellulose diacetate. That is to say, the angle between the direction of the transition moment of this dye and the molecular chain of these polymers is in the range from 24.5° to 27.5°.