viii Philip Guerrero
model is developed for a dispersed copolymer solutions while under the
conditions of micelle formation, scaling approach is used to briefly discuss the
critical micelle concentration and the aggregation number based on selected
reports from the literature.
Chapter 2 – The adsorption of polyelectrolytes onto charged surfaces
plays a central role in many technological areas, including: modification of
adhesion and wetting, increase of lubrication and friction reduction. The
careful control of the processes involved in the polyelectrolyte adsorption onto
solid surfaces is essential for the development of applications in several
fields: cosmetic, drug delivery, biomaterials and oil recovery. Therefore, the
understanding of the different variables (e.g., ionic strength, pH, temperature,
etc.) that modify the balance of interactions governing the adsorption of
polyelectrolytes is a scientific challenge for both basic and applicative
purposes. The aforementioned variables are mainly related to the modification
of the charge density of both polymer and surface, playing a key role on the
control of the different contributions involved in the formation of the layers:
electrostatic, specific, entropic, etc. This Chapter presents a comprehensive
study of the complex physico-chemistry associated with the adsorption of
polyelectrolyte layers, both single layer or multilayers formed for oppositely
charged polyelectrolytes, onto solid surface, paying special attention to the
adsorption of polyelectrolytes onto charged surfaces.
Chapter 3 – The authors present the complexation of the
linear, inherently hydrophobic, anionic polyelectrolyte poly[sodium
(sulfamate/carboxylate)isoprene] (SCPI) with the cationic surfactant
dodecyltrimethylammonium bromide (DTMAB), studied mainly by light
scattering methods. At low surfactant concentrations the polyelectrolyte
aggregates (already formed in surfactant-free solutions) shrink, whereas at
higher surfactant concentrations secondary aggregation takes place leading to
a strong increase in scattered intensity and a twofold increase in size. The
charge of the aggregates decreases abruptly in the first complexation regime
while more mildly in the second one as observed by ζ-potential measurements
in electrophoretic light scattering. The resulting polyelectrolyte-surfactant
complexes are fairly monodisperse (compared to the initial polyelectrolyte
aggregates) and they contain well-defined hydrophobic domains (proof of
complex coacervate phases) as shown by pyrene fluorescence probing. The
system under study is proved to have tunable complexation properties not
only by its dependence on surfactant content, but also by the effect of dilution
upon already formed complexes, which shows a gradual decrease in the
hydrophobic domains and a variation of the complexes size.