Adsorption and surface elastic properties of corresponding fluorinated andnonfluorinated cationic polymer films measured by drop shape analysis

Two different types of cationic polysoaps together with their monomers were synthesized with divalent quaternary ammonium repeat units carrying a hydr ocarbon or a fluorocarbon side chain, respectively. Dynamic surface tension s and surface dilatational rheology were measured by means of drop shape an alysis of a sessile bubble, using specially developed hardware and software . Surface dilatational rheology was measured by the oscillating bubble meth od. Both the monomers and polymers show strong surface activity. The hydroc arbon monomer shows a maximum surface pressure of 44 mN m(-1) and the fluor inated monomer one of 55 mN m(-1). The polymers show lower surface pressure s, 28 and 47 mN m(-1) for the hydrocarbon and fluorocarbon polymers, respec tively. The fluorinated polymer has peculiar adsorption characteristics, es pecially at low concentrations. All substances have very high surface dilat ational elasticity, up to 180 MN m(-1) for the fluorinated polymer, while t he hydrocarbon substances give approximately half of this value. The specif ic surface areas are relatively high, and adsorption of all these substance s is considerably slower than for ordinary surfactants, probably clue to th eir particularly bulky headgroup and charged nature. The monomers form mice lles with cmcs of 0.3 and of 3.0 g L-1 for the fluorinated and hydrocarbon monomer, respectively. With increasing bulk concentration, a maximum in sur face elasticity is observed for the monomers, but this decreased to almost zero at high concentrations. Both this decrease and the most of the frequen cy dependence of the modules are believed to be caused by molecular transpo rt between the surface and the bulk. It is more pronounced for the monomers than for the polymers. Deviations from the transport theory are observed a nd are believed to be caused by in-surface relaxation processes.