Transition to adsorbing polymers and two adsorption cases

In Ref. [42], PEO was embedded in a w/o-droplet microemulsion and studied by small-angle neutron scattering. The authors state that this polymer does not adsorb considerably at the SDS monolayer. The important statement is that both the size polydispersity and the shape fluctuations are increased compared to the reference system without polymer. Larger shape fluctuations are also found for gelatine embedded in w/o-droplet microemulsions (see Fig. 4.10 in [43]). Here, by strong confinement, the elongated shapes 

Reference [42] also reported on the hydrophilic polymer PNIPAM which is adsorbed at the outer interface of o/w-droplet microemulsions. Here, the fluctuations are increased 

Another study [54] considers the molar mass dependence of droplet size fluctuations in a water-n-octane-AOT-PEO system by small-angle neutron scattering. The polydispersity increases upon increasing the molar mass and the polymer content. Usually [44], this is accompanied by larger shape fluctuations, which would make this a case 2 system. Unfortunately, shape fluctuations were not considered here. 

The droplet size is considered in several references [55-58]. The works of Suarez considered water-decane-AOT-l-propanol(l-butanol)-PEO and water-cyclohexane-SDS-l-pentanol-PEO systems and found that the droplet size decreases as a function of the polymer content. The latter works of the Brown group considered water-cyclohexane- 

SDS-l-pentanol-PEO and water-toluene-SDS-l-pentanol-PEO systems and they found an increasing droplet size as a function of the polymer content. Controversial discussions followed [59,60]. If the elastic moduli were the only affected magnitudes one would argue With increasing bending rigidity ( case 1 ) the fluctuations would be diminished, and the radius would decrease due to the opposite surface-to-volume effects. The opposite trends would support case 2 . However, the size could also be changed by polymer incorporation inside the surfactant layer or by polymer-surfactant complexes inside the water domains. These effects would influence the droplet size differently. 

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