The intrinsic viscosities of the oligomeric propylene glycols in water agree well with [q] values computed for a tightly packed disc-coil model over the temperature range 9.5 to 59.0 "C. The observed decreases in intrinsic viscosity with increasing temperature can be ascribed to desolvatiou of the disc-coiled chain.
ZUSAMMENFASSUNG:Die Grenzviskositatszahlen der oligomeren Propylenglykole in Wasser stimmen gut mit den [ql-Werten uberein, die fur ein dichtgepacktes Scheibenmodell fur den Temperaturbereich von 9,5 bis 59,O"C berechnet wurden. Der beobachtete Abfall der Grenzviskositatszahl mit steigender Temperatur kann der Auflosung der scheibenformig angeordneten Kette zugeschrieben werden.
synopsisSuspensions of microcrystalline cellulose particles were flocculated with two cationic ionene polymers differing only in charge density. A comparison of the flocculation (residual absorbance) and electrophoretic data showed that optimum destabilization corresponded to neutralization of the particle charge and that both polyelectrolytes had the same flocculating ability on a charge basis. These results, when combined with specific adsorption measurements, suggest that flocculation of the cellulose particles is accomplished by a recently proposed, "mosaic" charge neutralization mechanism.
Intrinsic viscosities of the oligomeric propylene glycols in water agreed well with [r;] values computed for a Stuart-Briegleb model chain folded spirally into a tightly coiled disk with most of the hydrophobic methyl groups in the center of the coil. Expanded models such as a loosely folded rod, doughnut, or flexible coil gave values of M for the 16-mer which were considerably higher than experiment.
Surface pressure‐area isotherms of cellulose triacetate and amylose triacetate at the air‐water interface were determined on a vertical and horizontal film balance. Both polymers show anomalous behavior on the vertical balance, including: higher compressibilities than obtained on the horizontal balance, movement of the vertical plate, and atypical hysteresis of the isotherms.
The behavior of the cellulose triacetate film is attributed to heterogeneous gelation of the monolayer at low pressures. A mechanism involving the lateral tilting of pyranose units at the interface and subsequent stabilization of the monolayer by van der Waal's interactions accounts for the properties of this film.
A helical conformation for amylose triacetate at the air‐water interface is proposed to explain the low compressibility of this monolayer.
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