AbstractPrevious studies [Langmuir, 2014, 30, 21, 6057?6063, Phys. Chem. Chem. Phys., 2017,19, 23869?23877] have shown that surfactants bearing highly-methylated alkyl tails (so-called ?hedgehog? groups) are able to reduce the limiting surface tension at the aqueous critical micelle concentration (CMC) to ?CMC ~24 mN m?1, which is considerably lower than for common n-alkyl tail surfactants (30?40 mN m?1). In the quest to develop even more effective and efficient non-fluorinated surfactants, this study introduces new amphiphiles having double and triple hedgehog tails and examines relationships between surfactant structure and aqueous solution properties. Of particular interest are links between ?CMC, the effective hydrophobic-tail layer density (?layer) and total number of carbon and silicon atoms in the hydrophobic tails (NC+Si). Interestingly, ?CMC is seen to depend on ?layer rather than NC+Si, and ?layer ~0.63 g cm?3 appears to be an optimal surface layer density for promoting low ?CMC. For.....