Perm-waved human hair: A thermo-rheologically complex, shape-memory composite

Franz J Wortmann, Celina Jones, Thomas J Davies, Gabriele Wortmann

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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.

Original languageEnglish
Pages (from-to)3831-3840
Number of pages10
JournalBiophysical Journal
Issue number17
Early online date29 Jun 2021
Publication statusPublished - 7 Sept 2021


  • human hair
  • permanent bending deformation
  • shape memory polymer
  • thermo-rheologically complex behaviour


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