When a polymer mixture of two types of polymers having different molecular weights are left to equilibrate, the polymer having the lower molecular weight migrates to the free interface. This phenomenon is known as surface migration. We present a theoretical framework to explain this phenomenon and to quantitatively predict the amount of material that migrates to the interface. In what follows, we provide a review of the background literature, emphasizing the phenomenology behind such a segregation process, the different theoretical developments including variational methods and self consistent field theory as well as the experimental techniques that have been used to measure the amount of material leeches as a function of parameters e.g. temperature, surface tension and the mixing parameter (that determines whether the bulk polymeric phase is mixed or phase separated). The main hypothesis presented in this thesis is that the elasticity of the polymer matrix through which the low molecular weight species migrates to the free interface is an important parameter that has not been taken into account so far. This raises the interesting possibility of controlling surface migration by tuning matrix rigidity by changing polymer elasticity with broad industrial applications.