Figure 8.

A plot of the contact angle ($\theta$) of the aqueous solution of OGP (curves 1–3), DDGP.(curves 4–6), DM (curves 7–9), SMD (curves 10–12) and SML (curves 13–15) calculated from Equation (2) (perpendicular orientation by the hydrophilic head toward the air phase), Equation (3) (perpendicular orientation by the hydrophobic tail of surfactant toward the air phase) or Equation (7) (parallel orientation of surfactant molecules toward the interface region).