From melt to solution: Scaling relations for concentrated polystyrene solutions

Abstract

The scaling relations established for the relaxation modulus of concentrated solutions of polystyrene (PS) in oligomeric styrene [Wagner, Rheol. Acta 53, 765–777 (2014); Wagner, J Non-Newtonian Fluid Mech. (2015)] are applied to the solutions of PS in diethyl phthalate (DEP) investigated by Bhattacharjee et al. [Macromolecules 35, 10131–10148 (2002)] and Acharya et al. [AIP Conf. Proc. 1027, 391–393 (2008)]. The scaling relies on the difference ΔTg between the glass-transition temperatures of the melt and the glass-transition temperatures of the solutions. ΔTg can be inferred from the reported zero-shear viscosities, and the Baumgaertel, Schausberger, and Winter (BSW) spectra of the solutions are obtained from the BSW spectrum of the reference melt with good accuracy. Predictions of the extended interchain pressure (EIP) model, which is based on the assumption that the relative interchain pressure in the melt and in the solutions is identical, are compared to the steady-state elongational viscosity data of PS/DEP solutions. The Rouse stretch relaxation times as calculated from the respective scaling relation are a factor of 2–3 higher than the Rouse time defined by the experimentally observed upturn of the elongational viscosity at WiR=ε̇ τR→1. This may be caused by DEP being a good solvent at room temperature and/or polymer degradation. Using the experimentally determined Rouse times, quantitative agreement is obtained between experimental data and model. Except for a possible influence of solvent quality, linear and nonlinear viscoelasticity of entangled PS solutions can thus be obtained from the linear-viscoelastic characteristics of a reference polymer melt and the shift of the glass-transition temperature between melt and solution.