  A recent study [Gainaru et al. PRL., 112, 098301 (2014)] of two supercooled
monohydroxy alcohols close to the glass-transition temperature showed that the
Debye peak, thus far mainly observed in the electrical response, also has a
mechanical signature. In this work, we apply broadband shear-mechanical
spectroscopy to a systematic series of octanol structural isomers,
x-methyl-3-heptanol (with x ranging from 2 to 6). We find that the
characteristics of the mechanical signature overall follow the systematic
behavior observed in dielectric spectroscopy. However, the influence from the
molecular structure is strikingly small in mechanics (compared to roughly a
factor 100 increase in dielectric strength) and one isomer clearly does not
conform to the general ordering. Finally, the mechanical data surprisingly
indicate that the size of the supramolecular structures responsible for the
Debye process is nearly unchanged in the series.
