DIFFUSION OF M-NITROANILINE INTO POLYACYLONITRILE

The diffusion of nonionic penetrant, m‐nitroaniline, into polyacrylonitrile was studied in detail on a range of temperature from 50.6°C to 95.0°C. The penetrant distribution in polymer is Fickian, which is different from that of cationic dye, Malachite Green reported earlier. The diffusion coefficient D increases with the rise of temperature. The sharp inflection point (72°C) of the Arrhenius plot, log D versus 1/T, corresponds to Tg of polyacrylonitrile in the presence of water, which is lower than that measured in the dry state by a dynamic mechanical testing method. The activation energy is constant below Tg (ca. 10 kcal/mole), suddenly reaches a maximum at Tg and then gradually decreases with increasing temperature. General trends of Arrhenius plot for different polymer–penetrant systems are discussed. The temperature dependence of penetrant diffusion above Tg can be described by a general form of the WLF equation, log aT = log (DTg/DT) = − C1g(T − Tg)/(C2g + T − Tg), where the values of C1g and C2g were calculated to be 4.03 and 24.54, respectively. A comparison was made between m‐nitroaniline and Malachite Green. The difference in the respective Tg and the constants C1g and C2g of the WLF equation in polyacrylonitrile is attributed to the size of the penetrants and their ionic character. The surface concentration increases below Tg and decreases above Tg with rise in temperature. Copyright © 1969 John Wiley & Sons, Inc.