A “permanent” bent shape can be imposed on a straight human hair by a two-stage reduction/oxidation (perm-waving) process. The process relies on the molecular level on sulfhydryl/disulfide interchange as bond exchange reaction (BER). We expected a well-documented transition temperature around 60°C to be the trigger for the shape memory (SM) process of perm-waved hair. We confirm the existence of the SM process as such and investigate its time and temperature dependence. The results show a two-stage SM behavior, implying two distinct variations of the BER. The model to fit the data contains two fractional, normalized, elastic bending rigidities, which are strictly compensatory. They show Arrhenius-type temperature dependence and a common activation energy (E_A) of ∼−12 kJ/mol. The characteristic relaxation time for the first SM process shows little, if any, temperature dependence (E_A = −4 ± 2.7 kJ/mol). This is in contrast to the second process (E_A = −58 ± 5.5 kJ/mol) but in line with the expected properties of the suggested BERs. None of the parameters shows any sign of the expected trigger transition (∼60°C). We hypothesize that this specific transition occurs only for large tensile deformations, when specific SS bonds in the intermediate filaments of hair are activated. There is thus no specific “trigger” transition for the SM behavior of bent, perm-waved hair.

可以通过两阶段还原/氧化（烫发）工艺将“永久”弯曲形状施加在直发上。该过程依赖于分子水平的巯基/二硫化物交换作为键交换反应 (BER)。我们预计 60°C 左右的充分记录的转变温度将触发烫发的形状记忆 (SM) 过程。我们确认了 SM 过程本身的存在，并研究了它的时间和温度依赖性。结果显示了两阶段的 SM 行为，这意味着 BER 有两种不同的变化。拟合数据的模型包含两个分数、归一化、弹性弯曲刚度，它们是严格补偿的。它们显示出 Arrhenius 型温度依赖性和共同的活化能（E _A）约-12 kJ/mol。第一个 SM 过程的特征弛豫时间几乎没有（如果有的话）温度依赖性（E _A  = -4 ± 2.7 kJ/mol）。这与第二个过程（E _A  = -58 ± 5.5 kJ/mol）形成对比，但符合建议的 BER 的预期特性。没有一个参数显示任何预期触发转换的迹象（~60°C）。我们假设这种特定的转变只发生在大的拉伸变形时，当头发中间细丝中的特定SS键被激活时。因此，对于弯曲的烫发的 SM 行为没有特定的“触发”过渡。