(180bv) Surface Segregation in Blends of Cyclic and Linear Chains

Blends containing polymers of the same repeat unit chemistry, but distinct molecular architecture are commercially important, primarily due to their rheological properties. Blending polymers with different chain architectures may also prove useful in controlling interfacial properties by controlling interfacial segregation. A Gaussian field theory (GFT) by Wu et al. ¹ predicts that in a blend of a linear polymer and a cyclic polymer having the same repeat unit and molecular weight, the cyclic will be preferentially segregated to the surface and interface and in a manner that does not vary with molecular weight. Investigations of the segregation with neutron reflectivity (NR) show that the degree of surface segregation of cyclic polystyrene (CPS) in such a blend is profoundly impacted by the molecular weight of the cyclic chain. For example, when the chains have a molecular weight of 2k, the linear polymer enriches the surface, while for much larger 37k chains, the cyclic polymer enriches the surface nearly in quantitative agreement with the GFT².  We are exploring the crossover between the behavior characteristic of low molecular weight, and that characteristic of high molecular weight.

References

1)         Wu, D.T.; et al. Macromolecules, 1996, 29, 7919.

2)         Wang, S.F. Ph.D. Dissertation, The University of Akron, 2011.