Application of Statistical Theory of Elastomers to Supercontracted Keratin Fibers

Supercontraction in lithium bromide solutions of wool, human hair, and kid mohair takes place in two distinct stages. Evidence is presented which suggests that the polypeptide chains in these fibers. after supercontraction in lithium bromide solution, reach a condition both at the end of the first contraction stage and at the end of the second stage when the chain segments between positions of cross-linking approximate a random configuration.

The mean number of amino acid residues in the chains between positions of cross- linking was calculated from degree of contraction data, assuming that the chains were randomly kinked. In addition, the number was calculated from stress-strain data, using a formula which has been derived for rubber. The values obtained in these two ways were in satisfactory agreement.

The nature and distribution of cross-linkages are briefly considered, and it is pointed out that the results are consistent with cystine analyses of the fibers.