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Effect of random and block copolymer additives on a homopolymer blend studied by small-angle neutron scattering

Authors

  • Gretchen Voge,

    1. Department of Chemistry, Pacific Lutheran University, Tacoma, Washington 98447
    Current affiliation:
    1. University of Maryland School of Medicine, Baltimore, Maryland 21201
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  • Kari Fosser,

    1. Department of Chemistry, Pacific Lutheran University, Tacoma, Washington 98447
    Current affiliation:
    1. Department of Chemistry, University of Illinois at Urbana–Champaign, Urbana, Illinois 61801
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  • Dean Waldow,

    Corresponding author
    1. Department of Chemistry, Pacific Lutheran University, Tacoma, Washington 98447
    • Department of Chemistry, Pacific Lutheran University, Tacoma, Washington 98447
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  • Robert Briber,

    1. Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20472
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  • Adel Halasa

    1. Corporate Research Division, Goodyear Tire and Rubber Company, 142 Goodyear Boulevard, Akron, Ohio 44305
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Abstract

Small-angle neutron scattering (SANS) has been employed to study a blend of polystyrene and polybutadiene modified by copolymer additives. SANS data from the one-phase region approaching the phase boundary has been acquired for blends modified by random and diblock copolymers that have equal amounts of styrene and butadiene monomers as well as a random copolymer with an unequal monomer composition. The binary blend is near the critical composition, and the copolymer concentrations are low at 2.5% (w/w). The data have been fitted with the random-phase approximation model (binary and multicomponent versions) to obtain Flory–Huggins interaction parameters (χ) for the various monomer interactions. These results are considered in the context of previous light scattering data for the same blend systems. The SANS cloud points are in good agreement with previous results from light scattering. The shifts in the phase boundary are due to the effects of the additives on the χ parameter at the spinodal. All the additives appear to lower the χ parameter between the homopolymers; this is in conflict with the predicted Flory–Huggins behavior. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3191–3203, 2004

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