Two semifluorinated alkanes (SFAs), differing in their fluorinated segment lengths (F6H18 and F10H19), were compared with typical surfactants (F8H10OH and C18OH) as regards their collapse mechanism. It has been found that analysis of the pi-A isotherms under different experimental conditions is insufficient for a reliable description of the collapse phenomenon, and the importance of the relaxation experiments complemented with Brewster angle microscopy observation has been emphasized in this respect. The applied nucleation-growth-collision model points out differences between typical (alcohols) and nontypical (SFAs) surfactants as regards the collapse mechanism. Our results indicate that for the collapse process the presence of the polar head group in the molecule is more important than the structure of the hydrophobic chain. (c) 2008 Elsevier Inc. All rights reserved.