Three high molecular weight samples of poly(isobuty1 methacrylate) designated as 937, SW63/0082, an3 SW62/0298 were obtained from Edgewood Arsenal, Maryland. Sample 937 has been fractionated a n l described1Ia) earlier. Initial investigations have shown that the solution viscosities were shear dependent. The three samples were subjected to centrifugation at constant velocity for various times. The intrinsic viscosity and molecular weight (Rw) dropped slightly for sample 937, but dropped drastically for the other two samples.The number average molecular weight (mn) remained constant for each sample under these conditions. In this presentation we have also shown the necessity for taking measurements a t low angles during light scattering measurements in order to obtain the correct molecular weight (&) for these bigh molecular weight species.
ZUSAMMENFASSUNG:Drei Proben von Polyisobutylmethacrylat mit bohem Molekulargewicht, 937 1n *), SW 63/0082 und SW62/0298, Edgewood Arsenal, Maryland, wurden verschiedene Zeiten hindurch bei konstanter Geschwindigkeit zentrifugiert. Erste Untersuchungen zeigten, daI3 die Losungsviskositfiten von der Scherkraft abhangig sind. Die Viskositatszahl und das Molekulargewicht (mw) der Probe 937 fielen leicht ab, ein starker Abfall jedoch wurde bei den beiden anderen Proben festgestellt. Das Durchschnittsmolekulargewicht (Ha) blieb unter diesen Bedingungen bei allen drei Proben konstant. Bei dieser Untersuchung haben wir auch gezeigt, dal3 es notwendig ist, Lichtstreuungsmessungen bei kleinen Winkeln zu machen, um bei diesen hohen Molekulargewichten einen genauen Wert des Molekulargewichts (P,) zu erhalten.
Poly(n‐docosyl methacrylate) was prepared by emulsion polymerization. Since the weight‐average molecular weight of the unfractionated material appeared to be unusually large, light scattering measurements were made in three solvents and at several temperatures. No evidence of association in solution was found. Values of average molecular weight, dimensions, and second virial coefficients are reported.
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