A total of 24 dicationic geminis surfactants were synthesized, having a 2-b
utynyl spacer and chain lengths varying from 8 to 18 carbons. Geminis with
more flexible butyl spacers were also synthesized for comparison purposes.
Tensiometry gave critical micelle concentration (cmc) values, surface activ
ity, and Gibbs areas. Film studies on the C-18 geminis gave liftoff and col
lapse areas. The acetylenic geminis behave normally with the log cmc values
decreasing linearly with chain length for all the dibromide salts. Anomalo
us behavior occurred, however, with the C-18 gemini having a butyl spacer.
It was found that cmc data correlate with spacer area, a relationship ascri
bed to packing constraints on curved surfaces and, possibly, to steric inhi
bition of ion binding. The effects are accentuated with the C-18 surfactant
s. Geminis with heterocyclic headgroups were examined.