The effect of water on the glass transition of human hair

The glass transition of human hair and its dependence on water content were determined by means of differential scanning calorimetry (DSC). The relationship between the data is suitably described by the Fox equation, yielding for human hair a glass transition temperature of Tg = 144°C, which is substantially lower than that for wool (174°C). This effect is attributed to a higher fraction of hydrophobic proteins in the matrix of human hair, which acts as an internal plasticizer. The applicability of the Fox equation for hair as well as for wool implies that water is homogeneously distributed in α‐keratins, despite their complex morphological, semicrystalline structure. To investigate this aspect, hair was rendered amorphous by thermal denaturation. For the amorphous hair neither the water content nor Tg were changed compared to the native state. These results provide strong support for the theory of a quasi‐homogeneous distribution of water within α‐keratins. © 2005 Wiley Periodicals, Inc. Biopolymers 81: 371–375, 2006 This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com