MISCIBLE POLYMER BLENDS

Both segmental and terminal relaxations in single-phase blends of two different polymers are known to be complex. Segmental motions, probed by NMR, dielectric spectroscopy (DS), and light scattering, show distinct temperature dependencies for the two blend components. Furthermore, the component which has the lower glass transition temperature often shows two distinct relaxations, indicating that concentration fluctuations create two distinct microenvironments for those segments to relax in. These segmental anomalies often complicate the terminal dynamics as well, as seen in tracer diffusion studies.

Oscillatory shear rheometry can probe the relaxation of polymers on time scales spanning the range from segmental motions to terminal relaxations of chains, with time scales between 10-2 s and 104 s (probed using frequencies between 10-4 and 102 rad/s). An example of loss modulus data is shown in Fig. 1 for the poly(ethylene oxide)(PEO)/poly(methyl methacrylate)(PMMA) system. Data at different temperatures have been shifted in frequency to superimpose in the terminal relaxation of PMMA. Clearly, the empirical time-temperature superposition principle does not apply for polymer blends.


Figure 1
This is very different from the blends of two different chain lengths of the same polymer, for which time-temperature superposition applies, and the viscoelastic reponse is well-understood in terms of tube models. This is demonstrated in Fig. 2, where the data for two pure components were fit to extract two parameters (entanglement spacing and friction coefficient). Then, the viscoelastic response of the blends was predicted with no adjustable parameters.


Figure 2
In miscible blends of two different polymers, the entanglement spacing is reasonably understood, but the friction coefficients of the two species are not. We are presently testing a simple new idea based on concentration fluctuations, which create dynamically heterogeneous environments in the blend.

This material is based upon work supported by the National Science Foundation under Grants DMR-9629901, INT 9800092, DMR-9977928 and DMR-0422079. Any opinions, findings and conclusions expressed in this material are solely those of the authors and do not necessarily reflect the views of the National Science Foundation.
 

PUBLICATIONS

  1. R.H. Colby "Linear Viscoelasticity of Polymer Blends": Poly(ethylene oxide) and Poly(methyl methacrylate)" Proceedings of the Tenth International Congress on Rheology, (P.H.T. Uhlherr, ed.), Vol. 1, 278 (1988).
     
  2. M. Rubinstein and R.H. Colby "Self-Consistent Theory of Polydisperse Entangled Polymers: Linear Viscoelasticity of Polmer Blends" J. Chem. Phys., 89, 5291 (1988).
     
  3. R.H. Colby "Breakdown of Time-Temperature Superposition in Polymer Blends" Polymer, 30, 1275 (1989).
     
  4. J.L. Viovy, M. Rubinstein and R.H. Colby "Constraint Release in Polymer Melts: Tube Reorganization Versus Tube Dilation" Macromolecules, 24, 3587 (1991).
     
  5. J.A. Zawada, C.M. Ylitalo, G.G. Fuller, R.H. Colby and T.E. Long "Component Relaxation Dynamics in a Miscible Polymer Blend: Poly(ethylene oxide)/Poly(methyl methacrylate)" Macromolecules, 25, 2896 (1992).
     
  6. G.G. Fuller, J.A. Zawada and R.H. Colby "Investigating Miscible Polymer Blend Dynamics with Optical and Mechanical Rheometry" J. Non Cryst. Sol., 172, 668 (1994).
     
  7. J.A. Zawada, G.G. Fuller, R.H. Colby, L.J. Fetters and J. Roovers "Measuring Contributions to the Dynamic Modulus in Miscible Polymer Blends" Macromolecules, 27, 6851 (1994).
     
  8. J.A. Zawada, G.G. Fuller, R.H. Colby, L.J. Fetters and J. Roovers "Component Dynamics in Miscible Blends of 1,4 Polyisoprene and 1,2 Polybutadiene" Macromolecules, 27, 6861 (1994).
     
  9. S.K. Kumar, R.H. Colby, S.H. Anastasiadis and G. Fytas "Concentration Fluctuation Induced Dynamic Heterogeneities in Polymer Blends" J. Chem. Phys., 105, 3777 (1996).
     
  10. R.H. Colby "Dynamics in Blends of Long Polymers with Unentangled Short Chains " J. Phys. II France, 7, 93 (1997).
     
  11. J.A. Pathak, R.H. Colby, S.Y. Kamath, S.K. Kumar and R. Stadler, "Rheology of Miscible Blends: SAN and PMMA" Macromolecules, 31, 8988 (1998).
     
  12. J.A. Pathak, R.H. Colby, G. Floudas and R. Jerome, "Dynamics in Miscible Blends of Polystyrene and Poly(vinyl methyl ether)" Macromolecules, 32, 2553 (1999).
     
  13. S. Kamath, R.H. Colby, S.K. Kumar, K. Karatasos, G. Floudas, G. Fytas and J.E.L. Roovers, "Segmental Dynamics of Miscible Polymer Blends: Comparisons of the Prediction of a Concentration Fluctuation Model to Experiment," J. Chem. Phys., 111, 6121 (1999).
     
  14. R. H. Colby "Dynamic Scaling Approach to Glass Formation,"Phys. Rev. E, 61, 1783 (2000).
      
  15. L. Kielhorn, R. H. Colby and C. C. Han, "Relaxation Behavior of Polymer Blends after the Cessation of Shear," Macromolecules, 33, 2486 (2000).
     
  16. H. S. Jeon, A. I. Nakatani, C. C. Han and R. H. Colby, "Melt Rheology of Lower Critical Solution Temperature Polybutadiene/Polyisoprene Blends," Macromolecules, 33, 9732 (2000).
     
  17. J.A. Pathak, R.H. Colby, S.K. Kumar and R. Krishnamoorti, "Dynamics of Melt Miscible Polymer Blends", in Proceedings of the XIIIth International Congress on Rheology, 1, 414 (2000).
     
  18. S. Salaniwal, R. Kant, R. H. Colby and S. K. Kumar, "Computer Simulations of Local Concentration Variations in Miscible Polymer Blends" Macromolecules, 35, 9211 (2002).
     
  19. S. Y. Kamath, R. H. Colby and S. K. Kumar, "Evidence for Dynamic Heterogeneities in Computer Simulations of Miscible Polymer Blends" Phys. Rev. E, 67, 010801(R) (2003).
     
  20. R. Kant, S. K. Kumar and R. H. Colby, "What length Scales Control the Dynamics of Miscible
    Polymer Blends?", Macromolecules, 36, 10087 (2003).
     
  21. J. A. Pathak, S. K. Kumar and R. H. Colby, "Miscible Polymer Blend Dynamics: Double Reptation Predictions of Linear Viscoelasticity in Model Blends of Polyisoprene and Poly(vinyl ethylene)", Macromolecules, 37, 6994 (2004).
     
  22. R. H. Colby and J. E. G. Lipson, "Modeling the Segmental Relaxation Time Distribution of Miscible Polymer Blends: Polyisoprene/Poly(vinylethylene)", Macromolecules, 38, 4919 (2005).
     
  23. E. Krygier, G. Lin, J. Mendes, G. Mukandela, D. Azar, A. A. Jones, J. A. Pathak, R. H. Colby,  S. K. Kumar, G. Floudas, R. Krishnamoorti, R. Faust, "Segmental Dynamics of Head-to-Head Polypropylene and Polyisobutylene in Their Blend and Pure Components", Macromolecules, 38, 7721 (2005).
     
  24. B. Farago, C. Chen, J. K. Maranas, S. Kamath, R. H. Colby, A. J. Pasquale, T. E. Long, "Collective motion in poly(ethylene oxide)/poly (methylmethacrylate) blends", Phys. Rev. E,72, 031809 (2005).
     
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