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Issue 5, 2012
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Factors affecting time–composition equivalence in ternary block copolymer/cosolvent systems

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Abstract

Time–temperature rheological equivalence is one of the most important and broadly used concepts developed with regard to the viscoelastic behavior of polymers. In this study, we explore the generality of an analogous relationship, time–composition equivalence, in several series of ternary block copolymer/cosolvent systems at ambient temperature. Of particular interest are triblock copolymers solvated with a miscible mixture of midblock-selective solvents to yield physical gels. Such gels, consisting of a midblock-rich network stabilized by glassy endblock-rich microdomains, exhibit remarkable elasticity. The copolymers employed here are styrenic thermoplastic elastomers, whereas the solvents include an aliphatic/alicyclic mineral oil and several different tackifying resins varying in molecular weight and, hence, viscosity. Despite changes in solvent properties, time–composition superpositioning (tCS) yields master curves wherein the composition shift factors consistently scale with cosolvent zero-shear viscosity. Corresponding scaling exponents vary linearly with copolymer concentration and change slope at a morphological transition. Failure of tCS at low frequencies can be largely avoided by implementing copolymers with high-molecular-weight endblocks.

Graphical abstract: Factors affecting time–composition equivalence in ternary block copolymer/cosolvent systems

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Publication details

The article was received on 04 Sep 2011, accepted on 14 Nov 2011 and first published on 19 Dec 2011


Article type: Paper
DOI: 10.1039/C1SM06672B
Soft Matter, 2012,8, 1334-1343

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    Factors affecting time–composition equivalence in ternary block copolymer/cosolvent systems

    A. S. Krishnan and R. J. Spontak, Soft Matter, 2012, 8, 1334
    DOI: 10.1039/C1SM06672B

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