Surface segregation in polymer blends of minimal difference in the components surface free energy

One of the most remarkable features of polymeric materials is the phenomenon of surface segregation in polymer blends whose components surface energies are similar in magnitude. Herein, we contribute to this field by considering (i) surface phase behavior in stereochemically asymmetric polymer blends and (ii) determination of the sign and magnitude of surface energy (gamma) difference for a pair of polymers differing only slightly in their gamma values. Specifically, we present experimental results obtained on the blends of isotactic and syndiotactic poly(methyl methacrylate) (i-PMMA/s-PMMA blends), revealing that the syndiotactic macromolecules segregate to both the polymer-air and polymer-solid (glass) interface, expelling their isotactic counterparts. Also, the contact angle results and their analysis by the use of Lifshitz-van der Waals/acid-base approach are presented for PMMA and polystyrene (PS), which reveal that the surface free energy of PS is 1.5 +/-1.1 mJ/m(2) higher than that of PMMA.