Energetic and entropic components of tension in elastomeric wool fibers

Tension against temperature data were obtained for both unreduced wool fibers and fibers in which some of the disulfide bonds had been reduced by a thiol. The measurements were done while the fibers contained a diluent. Coefficients of volume thermal expansion were also measured. From the results the ratio of the energetic component of tension to the total tension (fe/f) was calculated. Most values of fe/f were within the range ± 0.20. In the case of unreduced wool fe/f changed from negative to positive as the extension increased. With a reduced sample containing 8% of the native disulfide, fe/f was negative and nearly constant over the range of extension employed. The change for unreduced wool follows from extension‐dependent interactions between polypeptide chains. The results indicate that, for unperturbed polypeptide chains from wool taken into solution following disulfide reduction, the end‐to‐end distance will decrease with increase of temperature, a partially extended form being the lower energy state.