The concentration required to reduce the surface tension of
pure water by 20 mN/m (C20) was used to determine the efficiency
of surfactant (PC20) which is the negative logarithm of C20.
Efficiency values of prepared cationic surfactants are calculated
and listed in Table 1. From these data, it was observed that
increasing the alkyl chain length and temperature, the efficiency
increase i.e., shift to lower concentration. Increasing the number of
methylene groups (–CH2–) along the hydrophobic chains,
increases the hydrophobicity of the molecules, hence water
hydrophobic interactions increase which decreases the surface
tension, followed by an increase in the effectiveness, as well as the
efficiency (lower concentration) [16].