Abstract
Theta solvents for polystyrene are prepared from high-viscosity blends of styrene and low-molecular-weight polystyrene, and then used to make dilute solutions with monodisperse polystyrene solutes of high-M = 2.3, 6.0, 9.0, 18.0 · 105. A Weissenberg rheogoniometer is used to measure the non-Newtonian viscosityη as a function of shear stressτ, for lowτ values, and also the complex viscosity componentsη′ andη″ as functions of frequencyω. A capillary viscometer is used for high-τ measurements ofη(τ). Viscometric properties, at room temperature, are analyzed as functions of high-molecular-weight solute concentrationc with parameters of constantτ orω to obtain [η(τ)], [η′ (ω)], and [η″ (ω)]. Such a collection of data has apparently not previously been available for polymers in theta solvents (in which Gaussian chain statistics prevail). Also unique is the achievement of high stress (τ = 2 ⋅ 104 Pa) at low shear rate, by virtue of high solvent viscosity which is not characteristic of other known theta solvents.
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