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

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.

Ultrastretchable, cyclable and recyclable 1- and 2-dimensional conductors based on physically cross-linked thermoplastic elastomer gels

“…(In previous studies, 41 the molecular weight characteristics of the copolymer reported by the manufacturer were provided.) For consistency with our previous TPEG studies, 37,42 an aliphatic : alicyclic (70 : 30) mineral oil (Hydrobrite 380) with a molecular weight of $500 Da was obtained from Sonneborn, Inc. and used without further purication. Reagent-grade toluene and hydrochloric (HCl) acid were purchased from Sigma-Aldrich and likewise used as-received.…”

Celebrating Soft Matter's 10th Anniversary: Simplicity in complexity – towards a soft matter physics of caramel

“…First, 'tuning' the composition and therefore the viscosity of the solvent of a polymeric system accesses different time scales. 33 For us, since the background sugar solution (70-87% sugar) is close to its glass transition, 21 we expect that viscosity is mainly 'tuned' by the (sugar : water) ratio.…”

Midblock-sulfonated triblock ionomers derived from a long-chain poly[styrene-b-butadiene-b-styrene] triblock copolymer

“…8 In the presence of miscible co-solvents with comparable block selectivity but different viscosities, these materials display evidence of time-composition equivalence. 9,10 For these reasons, they are uniquely suitable for use as shockabsorbing media and energy-efficient electroelastomers. [11][12][13] Conversely, in sulfonated block copolymers, a polar blockselective solvent such as water can be added to swell these materials for potential use as polyelectrolyte membranes (PEMs) 14 or as ionic electroactive polymers.…”