Binary blended polymers, surface segregation

Most of the cases discussed above are related to the use of polystyrene, but surface segregation is a universal phenomenon and can be transposed to other systems. Table 5.3 reports a non-exhaustive list of binary blends in which segregation occurred and in which the surfaces were decorated with functional groups. End-functional fluoro polymers are commonly developed via different chemistries (ring opening, controlled radical or anionic polymerization) and used as surface... 

Hyperbranched and comb polymers have also been used as surface active additive. Ariura et al. synthesized by combination of anionic and cationic polymerization a monodispersed hyperbranched polystyrene [73]. The authors proved by combination of DSIMS and neutron reflectivity the preferential surface enrichment of the branched protonated macromolecules when blended with its deuterated linear polystyrene counterparts with the same molar mass. Other systems involving the segregation of the branched macromolecules in binary blends were demonstrated such as in polyamide [74] or poly (methylmethacrylate) [75]. 

A crucial aspect on polymer blends containing block copolymers concerns the concentration of block copolymer both in bulk and at the surface. The former can be controlled in the design of the initial blend and the latter depends not only on the amount initially introduced in the blend but also on the eventual surface segregation. In Fig. 5.18 is schematically illustrated the block copolymer arrangement of binary blends with variable amount of block copolymer. At low concentrations (a, b) the block copolymer can reside either in the bulk or at the interface and the amount of block copolymer segregated at the interface is directly related to the... 

Genzer, J., Faldi, A., Composto, R.J. Self-consistent mean-field calculation of surface segregation in a binary polymer blend. Phys. Rev. E Stat. Phys. Plasmas Fluids 50, 2373-2376(1994)... 

The wall-PRISM theory has also been implemented for binary polymer blends. For blends of stiff and flexible chains the theory predicts that the stiffer chains are found preferentially in the immediate vicinity of the surface [60]. This prediction is in agreement with computer simulations for the same system [59,60]. For blends of linear and star polymers [101] the theory predicts that the linear polymers are in excess in the immediate vicinity of the surface, but the star polymers are in excess at other distances. Therefore, if one looks at the integral of the difference between the density profiles of the two components, the star polymers segregate to the surface in an integrated sense, from purely entropic effects. 

---