EFFECT OF PARTICLE-SIZE AND POLARITY OF LONG-CHAIN MOLECULES IN POLYMERIC FILMS ON THE SUPERCOOLING TEMPERATURE

We studied the effect of particle size and polarity of long-chain mole cules on supercooling when dispersed in polymeric films. Supercooling of the molecules of greater than 20 degrees C, which plays a key role in the thermoreversible response of recording media, was not observed for the molecules alone but occurred only when the molecules formed pa rticles dispersed in a polymer. As the size of particles grew from 0.1 -1.0 mu m to 3.5 mu m, the degree of supercooling of behenic acid disp ersed in a copolymer of vinyl chloride and vinyl acetate decreased fro m 30-40 degrees C to about 20 degrees C. The degree of supercooling al so decreased from 21-41 degrees C to 8-17 degrees C as the polarity of the molecules decreased from fatty acids to fatty alcohols to alkanes . On the other hand, the degree of supercooling increased from 20 degr ees C to 43 degrees C as the polarity of the polymer matrix increased. This large supercooling effect may be caused by the interaction betwe en the molecules and the polymers which depends on the polarity of bot h the long-chain molecules and the polymers.