Molecular packing of highly fluorinated phosphatidylcholines in monolayers

Surface pressure-area isotherms of a series of fluorinated DFnCmPC phosphatidylcholines bearing two acyl chains ended by a perfluoroalkyl Fn tail of variable lengths were recorded at the air-water interface. The limiting molecular areas (Ax), the collapse pressures (pi c), the pressures of the liquid-expanded to liquid-condensed phase transition (pi t) and their associated Ac and At areas were deduced from these experiments and compared to those of their hydrocarbon DMPC, DPPC and DSPC analogs. The impact of the fluorinated tails on the characteristics of phosphatidylcholine monolayers, as well as the dependence of the observed effects on the length of these tails and their relative weight with respect to the whole hydrophobic chain length, i.e. the degree of 'fluorination' of the monolayer, is interpreted in terms of steric hindrance, hydrophobicity and chain-chain interaction balance.