Aqueous mixtures containing a homo
polymer,
poly(vinyl
pyrrolidone) (PVP), or a hydro
phobically modified graftco
polymer, HM-
pullulan, (PULAU
9, where 9 stands for the nominal substitution degree), and different Gemini surfactantshave been investigated at 25.0
C. A wide variety of ex
perimental conditions were addressed by changing the amountof
polymer and of surfactant. The Gemini surfactants were synthesized,
purified, and characterized by routine methods.They differ from each other in
polar head grou
ps (two sulfonate-, two quaternary ammonium-, or two arginine-basedgrou
ps), in alkyl chain length (11 or 12 carbon atoms), and in the distance between the
polar head grou
ps. The s
pacersconsist of 2, 3, and 6 methylene units or 3 oxyethylene units. Surface activity and solution calorimetry measurementsyield some
physicochemical features inherent to micelle formation and
polymer-surfactant interactions. The data aresu
pported by ionic conductivity, detecting the critical thresholds and quantifying the modifications in binding associatedwith critical association (CAC) and micelle formation (CMC
*). The Gibbs energy of transfer from the micelles to a
polymer-binding site,
Gtrans, was evaluated from the CAC/CMC
* ratios versus the amount of added
polymer. Asimilar
procedure determined the enthal
py of transfer,
Htrans.
Gtrans decreases with added
polymer, whereas
Htransbecomes more negative on increasing the amount of
polymer in the medium. According to the selected data
presentedhere, cationic Geminis do not interact with PVP, while significant interactions have been observed in other surfactants.In mixtures with PULAU
9, the interaction is significant for all Geminis. This effect is due to interactions betweenthe surfactants and the hydro
phobic alkyl grou
ps on the main
polymer chain. The
pendent grou
ps facing away fromthe
polysaccharide chain act as binding sites for aggregates onto such
polymers.