Nitrate, uranyl, polymerization

Chemical analyses reveal that measurable amounts of uranyl ion are actually present in Pu(IV) polymers grown in mixtures of Pu(IV) and uranyl nitrate suggesting that uranyl ion is being taken up in the polymer network and consequently hampers the growth through a chain termination process as suggested in Fig. 3. The uranyl serves to terminate active sites because it does not typically form extensive polymeric aggregates as does Pu(IV) instead it tends only to dimerize and, at most, tri-merize (4). 

Concentration dependence, polymerization of hydrolysis products with uranyl nitrate.231, 237-39... 

Photopolymerization of acrylamide by the uranyl ion is said to be induced by electron transfer or energy transfer of the excited uranyl ion with the monomer (37, 38). Uranyl nitrate can photosensitize the polymerization of /S-propiolactone (39) which is polymerized by cationic or anionic mechanism but not by radical. The initiation mechanism is probably electron transfer from /S-propiolactone to the uranyl ion, producing a cation radical which propagates as a cation. Complex formation of uranyl nitrate with the monomer was confirmed by electronic spectroscopy. Polymerization of /J-propiolactone is also photosensitized by sodium chloroaurate (30). Similar to photosensitization by uranyl nitrate, an election transfer process leading to cationic propagation has been suggested. 

Copolymers of vinyl chloride-vinyl bromide were prepared in bulk using the same conditions in the preparation of PVC, except that only uranyl nitrate was used as in initiator with visible light to avoid photodegradation during polymerization. Thermal analysis of the copolymer indicated random placement of the two comonomers. 

Macroporous anion-exchange resin, useful for the sorption of uranyl nitrate, has been prepared by suspension polymerization of 4-methyl-2-vinylpyridine with trimethylene glycol dimethacrylate... 

Block copolymers, in w hich one part of the chain is made up entirely of residues of one type, the next part entirely of the other sort, and so on, can be conveniently made by emulsion methods (62). For example, if only the monomer A is water-soluble, the polymer radicals which are initially generated in this phase consist of short chain —A—A— A—A—A—A—. If these then diffuse to the phase boundary of droplets of the water-insoluble B monomer, further addition to the chain will occur to give the polymer B—B—B—B—B—B—A—A—A—A—A—A— B—B—B—B—B—B—B. This is the required block copolymer. As an example of this type of polymerization, acrylic acid ( A ) and styrene ( B ) give a block copolymer if the initial polymerization in the aqueous phase is catalyzed by the photosensitizer uranyl nitrate. 

Irradiation of a donor monomer-electron acceptor charge transfer complex, e.g. N-vinylcarbazole-sodium chloroaurate (2), -nitrobenzene (2) or -p-chloroanil (3) and -p opiolactone-uranyl nitrate (h), results in the initiation of cationic polymerization. 

With uranyl nitrate as a photosensitizer, vinyl chloride was polymerized at low temperatures using a tungsten-iodine lamp as the radiation source. Since this lamp produces primarily visible light, degradation of the polymer was minimized. The degree of crystallinity of the resulting polymer was said to be inversely related to the polymerization temperature [176]. 

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