Viscosity of aqueous and alkaline solutions of poly(ethylene oxide)

Abstract

AbstractViscosity measurements over a wide range of temperature were made on aqueous solutions of poly(ethylene oxide) samples of different molar mass and of low polydispersity. Above ca. 308 K the Mark‐Houwink exponent decreases and tends to a value of 0,50 at a lower critical solution temperature of 376 ± 2 K. The same value for this θ‐temperature is derived also as that at which the slope of Stockmayer‐Fixman plots tends to zero. At 298 K the unperturbed dimensions [〈r2〉0/M]1/2 = 0,089 nm · g−1/2 · mol1/2 and their temperature coefficient d ln 〈r2〉0/dT ≈ − 1,5 (±0,5) · 10−3 K−1. In aq. KOH the intrinsic viscosity [η] is virtually uninfluenced by pH at low‐medium pH, but at high pH, [η] falls sharply. Viscosity and phase separation measurements yield θ‐conditions in 1,24 M aq. KOH at 298 K. The derived polymer‐water interaction parameters χ increase from 0,449 at 276 K to 0,493 at 358 K, but the enthaplic component χH is incapable of yielding a meaningful value for the solubility parameter δ2 of the polymer in such a hydrogen‐bonding system. The calculated value of χ2 was 18,9 (kJ · dm−3)1/2.