Diffusion ofm‐nitroaniline into polyacylonitrile

摘要

AbstractThe 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 coefficientDincreases with the rise of temperature. The sharp inflection point (72°C) of the Arrhenius plot, logDversus 1/T, corresponds toTgof 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 belowTg(ca. 10 kcal/mole), suddenly reaches a maximum atTgand then gradually decreases with increasing temperature. General trends of Arrhenius plot for different polymer–penetrant systems are discussed. The temperature dependence of penetrant diffusion aboveTgcan be described by a general form of the WLF equation, logaT= log (DTg/DT) = −C1g(T−Tg)/(C2g+T−Tg), where the values ofC1gandC2gwere calculated to be 4.03 and 24.54, respectively. A comparison was made betweenm‐nitroaniline and Malachite Green. The difference in the respectiveTgand the constantsC1gandC2gof the WLF equation in polyacrylonitrile is attributed to the size of the penetrants and their ionic character. The surface concentration increases belowTgand decreases aboveTgwith rise