Free surfaces of polymer blends. II. Effects of molecular weight and applications to asymmetric polymer blends

Hariharan, Arvind; Kumar, Sanat K.; Russell, Thomas P.
September 1993
Journal of Chemical Physics;9/1/1993, Vol. 99 Issue 5, p4041
Academic Journal
The composition of the free surface of a binary polymer blend has been investigated in this work as a function of molecular weights, energetic parameters, and composition. The approach involved the use of a compressible mean-field lattice model that was developed in the spirit of the Scheutjens and Fleer theory of polymer solutions [J. Chem. Phys. 98, 6516 (1993)]. For symmetric polymer blends it was found that the surface segregation was driven by the degree of incompatibility of the blend, with the segregation increasing monotonically with the quantity χ1,2 r. These results are in qualitative agreement with conclusions obtained from an incompressible model for polymer blends near a surface, and suggests that the inclusion of compressibility effects do not change the predicted surface segregation significantly in these cases. In contrast, the behavior of isotopic polymer blends of disparate molecular weights, which could not be reproduced in the case of incompressible models, can be captured by the compressible model [J. Chem. Phys. 98, 4163 (1993)]. This fact therefore stresses the importance of compressibility effects in the context of segregation to free surfaces, especially for blends of disparate molecular weight polymers, and suggests that such models have to be utilized to incorporate all of the physics in these situations.


Related Articles

  • Fabrication of polymer nanodots with single electron patterning technology. Yoshimura, Toshiyuki; Shiraishi, Hiroshi; Yamamoto, Jiro; Terasawa, Tsuneo; Okazaki, Shinji // Applied Physics Letters;3/25/1996, Vol. 68 Issue 13, p1799 

    Details the fabrication of polymer nanodots with single electron patterning technology. Use of conventional polymer resists; Difference between the resists; Association of the nanodot sizes with the molecular-weight distribution characteristics of the resin polymers.

  • A universal coexistence curve for polymer solutions. Sanchez, Isaac C. // Journal of Applied Physics;10/15/1985, Vol. 58 Issue 8, p2871 

    Examines a universal coexistence curve for polymer solutions. Symmetrization procedure; Features of the universal coexistence curve; Coexistence diameter.

  • Deviation from mean-field behavior in a low molecular weight critical polymer blend. Hair, D. W.; Hobbie, E. K.; Nakatani, A. I.; Han, C. C. // Journal of Chemical Physics;6/15/1992, Vol. 96 Issue 12, p9133 

    A deviation from mean-field behavior is observed in the static susceptibility and correlation length measured with small angle neutron scattering as a function of temperature near the phase boundary of a relatively low molecular weight critical polymer mixture. The possibility of a fluctuation...

  • Structure of the polymer–solvent interface. Miles, Danny G.; Schmidt, James W. // Journal of Chemical Physics;3/15/1990, Vol. 92 Issue 6, p3881 

    The first measurements of ellipticities ρ from the liquid–liquid interface between polymer and solvent mixtures near their consolute points are reported. When scaled according to theory the ellipticities of high molecular weight polystyrene + solvent mixtures are consistent with those...

  • X-ray reflectivity on perfluoropolyether polymer molecules on amorphous carbon. Toney, Michael F.; Thompson, Carol // Journal of Chemical Physics;3/15/1990, Vol. 92 Issue 6, p3781 

    The mass density profile from thin (∼25 Å) layers of polymer molecules adsorbed on amorphous carbon thin films is determined from measurements of the specular reflectivity of x rays. Important information on the conformation of the polymer molecules is obtained from the density profile...

  • Improved expression of mean-square radius of gyration. I. Vinyl polymers. Zhou, Zhiping; Yan, Deyue // Journal of Chemical Physics;3/15/1992, Vol. 96 Issue 6, p4792 

    Taking account of the effect of large side groups, the mean-square radius of gyration of vinyl polymer chains has been deduced by the method of matrix algebra. According to previous approaches to the computation of conformational energy, every substituent of vinyl polymer is confined to an...

  • Solid friction in gel electrophoresis. Burlatsky, S. F.; Deutch, John M. // Journal of Chemical Physics;11/8/1995, Vol. 103 Issue 18, p8216 

    We study the influence of solid frictional forces acting on polymer chains moving in a random environment. We show that the total reduction in the chain tension resulting from the small friction between a polymer and fixed entanglement points is a steep nonlinear function of the number of...

  • Mutual diffusion in a compatible mixture of unentangled polymers. Variation with molecular weight. Kanetakis, J.; Fytas, G. // Journal of Chemical Physics;10/15/1987, Vol. 87 Issue 8, p5048 

    Presents a study on mutual diffusion in compatible mixture of unentangled polymers. Derivation of equations; Characteristics of enhanced mutual diffusion with variation in molecular weights; Use of photon correlation technique.

  • The effects of cross-linking on the equation of state of a polymer solution. Horkay, F.; Hecht, A. M.; Geissler, E. // Journal of Chemical Physics;8/15/1989, Vol. 91 Issue 4, p2706 

    Measurements of the swelling pressure ω and shear modulus Gs in a set of poly(vinyl acetate) networks swollen to different degrees in toluene and in acetone are reported, using solutions of the uncross-linked polymer to obtain deswelling under known conditions of osmotic pressure. The...


Read the Article


Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics