No abstract

Viscosity, osmotic pressure and light scattering measurements have been carried out on fractions of poly p-chlorostyrene. The viscosity-molecular weight relationships have been established. The KUHN-HOUWINK constants obtained by different workers show wide divergence. However, the constant K s obtained by different workers from different extrapolation methods, is in good agreement with the value of 5.2.10-4. The same value is obtained u s i n g [+]R, the ordinate at the common point of intersection of the In qr/c us. c plots for the same polymer in different solvents. ZUSAMMENFASSUNG: An Fraktionen von Poly-p-chlorstyrol wurden Messungen der Viskositat, des osmotischen Drnckes und der Lichtstreuung durchgefiihrt. Die Beziehungen zwischen Viskositat und Molekulargewicht wurden ermittelt. Die KuHN-HOuWINK-Konstanten, die von verschiedenen Autoren erhalten wurden, weichen stark voneinander ab. Hingegen steht die von mehreren Bearbeitern durch verschiedene Extrapolationsmethoden erhaltene Konstante KQ in guter ifbereinstimmung mit dem Wert von 5,2.lO-4. Der gleiche Wert wird erhalten, wenn man die Ordinate des gemeinsamen Schnittpunktes ( [ q ]~) in der Auftragung von In qr/c gegen c fiir das gleiche Polymere in verschiedenen Losungsmitteln gebraucht.

Six unfractionated samples of polyacrylamide were hydrolysed to varying extents. The partially hydrolysed polyacrylamides were investigated by viscosity, osmotic pressure and light scattering techniques in 0,12 M NaCl. The molecular weights of the hydrolysed polyacrylamides confirmed the absence of main chain degradation during hydrolysis. Intrinsic viscosities and dimensions increased with increasing extent of hydrolysis. On correlating the intrinsic viscosities with the extent of hydrolysis, a linear relationship between intrinsic viscosities and the squareroot of the extent of hydrolysis was obtained. a) NCL Communication No. 3325

The alkaline hydrolysis of polyacrylamide in solution is studied viscosimetrically. The viscosity of the solution increases continuously during the course of hydrolysis. The relationship between intrinsic viscosity and the extent of reaction is established, using a series of polyacrylamides with known extents of hydrolysis. The extent of reaction is determined from the observed flowtime, using the relationship between [ r ] ] and extent of reaction. The second-order rate constant and the activation energy are in good agreement with those reported in the literature. A four-fold increased reactivity of the amide groups towards hydrolysis is observed at very low extents of hydrolysis.

High molecular weight polyacrylamides were synthesized and successfully modified to contain up to 8.3% hydroxamate functional groups. The selective flocculation tests carried out on I : 1 iron oxide/kaolin mixtures using parent polyacrylamide, polyacrylic acid and the modified polyacrylamide, confirm the possibility of enhancing selectivity through introduction of iron chelating functional groups in commercially available polymers. Starting with a feed grade of 35% iron, 92% recovery with acceptable grade of 60% iron has been achieved using the modified polyacrylamide.