Interfacial Strengthening with Random Copolymers

  • S. T. Milner
  • G. H. Fredrickson

Abstract

Recent experiments show increased interfacial strength of interfaces between immiscible A and B homopolymers when A/B random copolymers (RCs) are added at the interface. These results have been interpreted in terms of the work of Garel et al., which predicts that RCs at such A-B interfaces will adopt conformations in which long loops (of order 1/χ2 monomers) slightly rich in A (B) monomers will be found on the A (B) side of the interface. We reexamine these results in light of a simple Flory-Huggins description, which shows that such RCs would be immiscible with either A or B homopolymer with an effective χ parameter χ eff=χ/4 for symmetric RCs, and would tend to collapse at the A-B interface. Thus, the RC-homopolymer interface would then be only as strong as an interface between homopolymers with χ=χeff, which would be strong only if the A-B interface is nearly broad enough to be self-entangled already. Alternatively, if the RCs have a broad composition distribution, they can segregate by composition in strata, producing a “graded” interface. We derive criteria for the RC composition distribution and layer thickness in order that the resulting interface be strong.

Keywords

Tube Diameter Random Copolymer Interfacial Strength Composition Distribution Interfacial Width 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer Science+Business Media New York 1997

Authors and Affiliations

  • S. T. Milner
    • 1
  • G. H. Fredrickson
    • 2
  1. 1.Exxon Research and EngineeringAnnandaleUSA
  2. 2.Dept. of Chemical EngineeringUniv. of CaliforniaSanta BarbaraUSA

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