Polyelectrolyte gels hydrophobic interactions

We have discussed the role of hydrogen bonding and hydrophobic interaction in the volume collapse of NIPA-AAc gels. However, one may claim that the gel system examined would be a special kind of polyelectrolyte gel. Thus we have tired further to examine the effects of both intermolecular forces on the gel transition with another polyelectrolyte gel. 

Urea, being a water structure breaker, would weaken the hydrophobic interaction between solute molecules as reported in several previous studies (see Ref. 76). It is thus necessary for us to examine the effects of urea on the hydrophobic interaction in the present gel system. However, this is a considerably difficult problem which, to our knowledge, has not yet been dealt with by any researchers in the field of polyelectrolyte gels. The main reason is the lack of information about whether hydrophobic interaction plays a role in the volume collapse of usual polyelectrolyte gels with a lot of hydrophilic ionizable groups, such as the LPEI gels in question. As a novel approach in order to overcome this difficulty, we examined the swelling curves of the LPEI gel as a function of the concentration of anionic surfactants in the presence and absence of urea. 

So, in the case of trivalent counterions the electrostatic interactions are so strong that the ion aggregation proceeds even in such polar media like water. The same behavior was observed in the less polar solvent methanol. Similar to the hydrophobic aggregates in polyelectrolyte gels, the ion aggregates (multiplets) begin to form when the gel still occurs in the swollen state (and remain in the gel upon collapse). 

Olga E. Philippova s main research interests are polyelearolyte and ionomer behavior of polymer gels, linear and cross-linked polyelectrolytes with associating hydrophobic groups, polymer gel/surfactant interactions, interpolymer complexes, and polymer gels with entrapp l linear stiff-chain macromolecules. 

When a highly swollen polyelectrolyte gel is immersed in an aqueous solution of a surfactant, the volume of the gel suddenly shrinks. Further, if a hydrophobic gel that does not swell in water is placed in the same solution, the gel swells. These phenomena are caused by the adsorption of the surfactant onto the gel. The adsorption of the surfactant onto the gel is caused by static interaction (when it is a polyelectrolyte gel) or hydro-phobic interaction. Gels can change from hydrophilic to hydrophobic and vice versa by interacting with surfactant molecules. As a result, the properties of the gel change drastically. There are many reports on the interaction between surfactants and linear polymers [26-29]. A Russian group reported on work on three-dimensionally crosslinked polymer gels [30-32], Later, other authors developed a worm-like device that moves... 

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