Radiotagged acrylamide was polymerized in a solution containing untagged polyacrylamide in order to study branch formation. Polymerizations were carried out at 50°C. and at 78°C. with a persulfate‐bisulfite catalyst. At 78°C., polymer with from one to seven branches was formed, while at 50°C. even with larger amounts of catalyst, the polymer was almost exclusively linear. The intrinsic viscosity of branched polyacrylamide, in water at 30°C., was compared with the predictions of the Zimm and Stockmayer equation for the intrinsic viscosity of trifunctionally branched molecules. This equation gave values which agreed well with measured values of the number of branches.

synopsisPolytetrafluoroethylene surfaces have been treated to reduce thrombogenicity in order to make them suitable for use in prosthetic devices that come in contact with blood. This was done by first etching the surface with potassium in liquid ammonia to produce double bonds and then using these double bonds as sites for grafting on polyacids or as sites for chemical reactions. Tubes 80 treated were tested for thrombogenetic activity by implantation in the thoracic aorta or inferior vena cava of dogs. These tests showed that the thrombogenicity of a polytetrafluoroethylene surface can be reduced by attaching negatively charged groups provided the surface concentration of these groups is not too high (order of 1-2 X 10-equivalent per cm* geometric area) and provided the distribution of these groups is uniform. Sulfonic acid groups obtained by chlorosulfonation and carboxyl groups attached by grafting krt-butyl crotonate and hydrolyzing to crotonic acid were effective. Long chains of poly(scrylic acid), poly-(ethylenesulfonic acid), and poly(viny1 alcohol) sulfate were less effective.

SynopsisLithium alkyls and phenylmagnesium bromide, in toluene, and lithium-naphthalene, in dimethoxyethane, polymerize tert-butyl crotonate. Sodium naphthalene produces only low polymer ( M , <3000), and potassium naphthalene gives no polymer. Even lithium naphthalene, which polymerized k t b u t y l crotonate readily, fails to polymerize tert-butyl tiglate. Free radicals polymerize neither tert-butyl crotonate nor twtbutyl tiglate. Poly(tertbuty1 crotonate) formed in the presence of lithium naphthalene is noncrystalline, in the presence of lithium alkyls, either noncrystalline or partly crystalline, and in the presence of phenylmagnesium bromide, highly crystalline. Poly(crotonic acid) was prepared from poly(kt-butyl crotonate).Polycrotonsaure wurde aus Poly-tert-butylcrotonat dargestetllt.

A catalytic alkoxylation process to make higher molecular weight poly(propylene oxide) and poly(propylene oxide-co-butylene oxide) polyols containing greater than 65% of primary hydroxyl end groups is described. The one-pot method employs the double metal cyanide catalyst and tris(pentafluorophenyl)borane catalyst (FAB) in a sequential manner and exploits the high primary hydroxyl regioselectivity of FAB over a broad range of temperatures. The process was carried out in two sequential steps: (a) DMC-catalyzed epoxide ring-opening polymerization at a temperature of >130 °C and (b) FAB-catalyzed regioselective capping at a temperature between 60 and 110 °C. The approach thus combines the relative advantages of both the DMC and FAB catalysts: high activity and high primary hydroxyl regioselectivity, respectively. It is also demonstrated that sufficiently low levels of FAB catalyst (e.g., 150 ppm) are sufficient, thus obviating the need for catalyst removal from the final product.