chloroform/ethanol mixture was necessary to dissolve the polystyrene-b-poly(acrylic acid)

dendrimer-like block copolymer sample. Other commonly used solvents include n-hexane,

benzene, diethyl ether, as well as mixtures such as for instance hexane-ethanol, benzene-ethanol,

or chloroform-methanol .s After spreading, the surface active block copolymers expand to form

an adsorbed monolayer that quickly covers the entire available area present between the barriers.

In addition to the A/W interface which is the most commonly studied interface, others are

possible such as oil/water interfaces or gas (different from air)/water interfaces.













Figure 2-2. A Wilhelmy plate partially immersed in a water subphase.

 The surface pressure measurements were achieved by use of the Wilhelmy plate technique

as shown in Figure 2-2.87 The surface tension (s)~ is defined by Equation 2-1,

 ai = To 7 = -A7 (2-1)

where To represents the surface tension of the water subphase in the absence of an adsorbed

monolayer, and 7 represents the surface tension of the water subphase in the presence of an

adsorbed monolayer. Water is a very interesting subphase when investigating monolayers since it

has an exceptionally high surface tension (- 73 mN/m at 20 oC and under atmospheric

pressure"') that allows a wide range of surface pressures to be obtained. When the Wilhelmy

plate is partially immersed into the subphase, the forces acting consist of gravity and surface