Complexes of Poly[Sodium(Sulfamate/Carboxylate)Isoprene] ... 97Figure 5. Hydrodynamic radius (a), scattered intensity (b) and I 1 /I 3 ratio (c) from
SCPI/surfactant complexes (solution with cDTMAB = 1.89x10-^4 g/mL) as a function of
dilution ratio (SCPI and DTMAB dilution occurs from right to left). Insert in c: I 1 /I 3
ratio for solution with cDTMAB = 2.81x10-^4 g/mL.
Diluting the complexes-containing solutions with distilled water causes
remarkable changes to the formed complexes. The hydrodynamic radius of
aggregates in the solution with cDTMAB = 1.89x10-^4 g/mL initially increases and
eventually drops towards a value corresponding to aggregates with no added
surfactant (Figure 5a). The initial increase of size is accompanied by a mild
decrease in scattered intensity which is a sign of partial disassembly of the
formed clusters (Figure 5b). The significant increase of Rh shows a
conformational change from a compact to an open structure possibly caused
by the release of surfactant from the aggregates. This way the system increases
its charge and decreases its hydrophobic content; both leading to an expansion
of the chains and their mutual distances. Finally, the scattered intensity drops
significantly i.e. the surfactant has abandoned the aggregates to a large extend
resulting to their break-up. The assumed release of surfactant molecules from
the aggregates is supported by the initially mild increase in I 1 /I 3 ratio and its
final abrupt increase to the level of the absence of well defined hydrophobic
regions for pyrene (Figure 5c) that experiences more polar environment [21].
It is important to emphasize that dilution provides a simple means for releasing
a pre-attached hydrophobic drug from the aggregates in a tunable way.