Hydrocolloids (Enhanced Edition‪)‬

The intermolecular forces between hydrophilic surfaces and molecular groups in aqueous
solutions ultimately determine the structure of 'complex fluid' structures such as gels and
biological assemblies composed of 'soft matter': surfactants, lipids, polyelectrolytes,
biopolymers and proteins. These forces also determine the dynamic properties of these
structures such as their non-equilibrium and time-dependent interactions, their shape
fluctuations, molecular exchange processes, and rheology. Because each type of interaction can
have very different effects at large and small separation, both quantitatively and qualitatively, it
is useful to distinguish between the long-range (colloidal) forces and short-range (adhesion)
forces. For example, the electrostatic interaction between two surfaces in water can be repulsive
at large separations (due to the 'double-layer' interaction) but attractive at small separations
(due to ion-correlation and complementary Coulombic interactions). Here, the different
interactions that occur in water and aqueous solutions will be critically reviewed in the light of
recent experiments and theoretical modelling.