Wettability, segregated polymer

As the use of aqueous base in the development step has been mandated, the wettability of resist films is very important and therefore water contact angles of polymer and resist films are measured often. The contact angle measurement can provide important information about surface segregation of blend films. 

Surface segregation, which is also a common phenomenon in other materials, has received limited attention and most of the studies applied this concept for the control of the surface chemical composition. Moreover, surface segregation has been typically considered as a non-desirable effect. This is particularly true in the case of materials with precise bulk properties provided by the presence of different additives such as plasticizers or UV-absorbers. The segregation of these additives towards the interface modifies the bulk properties and can provoke large variatiOTis on their mechanical behavior. Several contributions have explored this phenomenon in order to reduce the amount of oligomers/polymeric additives that bloom to polymer surfaces [13]. However, in many other applications it is desirable to have surface properties that vary to a large extent from those found in the bulk. For example, to favor adhesion or increase the wettability, or the opposite, i.e., increase the hydrophobicity, to improve the biocompatibility of commercial polymers or to enhance the chemical resistance. 

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