Grafting ceric ammonium nitrate

This technique is based in the fact that when cellulose is oxidized by ceric salts such as ceric ammonium nitrate Ce(NH4)2(N03)6 free radicals capable of initiating vinyl polymerization are formed on the cellulose. However, the possibility remains that the radical formed is an oxygen radical or that the radical is formed on the C-2 or C-3 instead of the C-6 carbon atom. Another mechanism, proposed by Livshits and coworkers [13], involves the oxidation of the glycolic portion of the an-hydroglucose unit. Several workers [14,15], however, have found evidence for the formation of some homopolymer. In the ceric ion method free radicals are first generated and are then capable of initiating the grafting process [16-18]. 

Graft polymerization of methylmethacrylate monomer onto pulps of different residual lignin contents using ceric ammonium nitrate as the initiator was carried out to study the influence of this residual lignin on the graft-ability of these pulps (Fig. 3). From this figure one can... 

Graft copolymerization of methylmethacrylate onto paper wood pulp using ceric ammonium nitrate as the initiator has been studied. Different experimental conditions have been used, including both water and water-organic solvent systems. The effects of composition of the grafting medium and grafting temperature on the grafting process are examined. 

Grafting of methylmethacrylate onto cellulose using ceric ammonium nitrate (Ce ) as the initiator in a benzene-water system is also demonstrated. The grafting yield in a benzene-water system is much lower than in the case of the methanol-water system and decreases by increasing the ratio of benzene to water. This can be due to the lower polarity and wetting power of benzene, which leads to poor swelling of the cellulose. 

Grafting and networking may modify the mechanical, chemical, and functional properties of polymers and enhance their utilization for some purposes, such as for water treatment (Kumar and Verma, 2007 Mishra et al., 2003). Psyllium derivatives were prepared by grafting acrylonitrile onto psyllium molecules using a ceric ammonium nitrate and nitric acid system (Mishra et al., 2003). The resulted grafted psyllium samples were not soluble in commonly used solvents or their combinations. In 2007, methacrylic acid derivatives of psyllium were prepared using ammonium persulfate as initiator and cross-linked using N,N-methylenebisacryla-mide as the crosslinker (Kumar and Verma, 2007). The modified psyllium... 

Gelatinizing starch under milder conditions (30 min at rather than 60 min at 95 C) has little effect on water absorbency. 4) A lower nitric acid concentration in the graft polymerization recipe (O.IH rather than l]f HNQs used to dissolve ceric ammonium nitrate) does not alter absorbency properties. 

Kamogawa, and Sekiya (54) studied the graft polymerization of acrylamide onto cotton fabric using ceric ammonium nitrate as the catalyst. Similarly to Kulkarni et al. (35) the authors performed subsequent cross-linking with formaldehyde amd methylol compounds. From precipitation studies by acidification of cuprammonium solutions on mixtures of polyacrylamide and cellulose on the one hand and polyacrylamide-cellulose grafts on the other the authors conclude that chemical bonds must exist between the two polymers in the grafted product. 

Scheme 7 a Reaction mechanism when sodium persulphate was used as hydroxylating agent for the polymer (P-H). b Decomposition of hydroxylated polymer P-OH at the surface, in the presence of ceric ammonium nitrate generated alkoxy radicals (P-0 ) which initiated the grafting... 

Figure 6. Effect of grafting time on the graft copolymerization of methyl methacrylate onto cellulose nitrate with ceric ammonium nitrate as initiator. (Reprinted, with permission, from Ref. 19. Copyright 1979, Wiley.)...

In the case of cellulose nitrate grafting initiated by ceric ammonium nitrate, grafting may probably be due to a complex... 

Acrylonitrile graft polymerizes readily with either granular or pasted starch to yield starch-g-polyacrylonitrile (PAN), and reactions are generally carried out in water with ceric ammonium nitrate as the initiating system CL). Reaction of starch-g-PAN with alkali at elevated temperatures converts the nitrile substituents of PAN to a mixture of carboxamide... 

Since the partial insolubility of the starch-ceric ammonium nitrate reaction product complicates the interpretation of solubility data, we ran a second series of graft polymerizations using cobalt-60 as an initiator in an attempt to remove this variable (Table II). If combination of PAN macroradicals is occuring during graft polymerization, it should occur during cobalt-60 initiated polymerizations as well as in those initiated by ceric ammonium nitrate. In the first four reactions of Table II, starch was irradiated as a water slurry under graft polymerization conditions, but in the absence of acrylonitrile, to determine the influence of different doses of irradiation on starch solubility. 

Both starch-g-PAN and starch-g-polyacrylamide were prepared by cobalt-60 initiation, since acrylamide does not graft efficiently in the presence of ceric ammonium nitrate (16). Both graft copolymers were irradiated with ultrasound to give totally soluble products the ultrasonic treatment of starch-g-PAN was carried out in DMSO, while that of starch-g-polyacrylamide was run in water. 

Graft Polymerization. Ceric Initiation. A stirred slurry of 10 g of starch in 200 ml of water was sparged with a slow stream of nitrogen for 1 hr at room temperature 15 g of acrylonitrile was then added, followed after 5 min by a solution of 0.338 g of ceric ammonium nitrate in 3 ml of IN nitric acid. In the reaction run with 1-hexanethiol, ceric ammonium nitrate solution was added first, followed after 5 min by a solution of 1.0 g of mercaptan in 15 g of acrylonitrile. The resulting mixture was allowed to stir for 2 hr at 25-27°C (temperature maintained with ice-water) and then was diluted with 200 ml of ethanol. The pH was adjusted to 6-7 with sodium hydroxide solution, and the polymer was isolated by filtration, washed with water and ethanol, and vacuum dried at 60°C. Ungrafted PAN was removed by repeated extraction of the polymer with dimethylformamide (DMF) at room temperature. 

Film Formation. Starch-g-PAN samples used for this study were prepared as described above, except that the small amounts of PAN homopolymer were not removed by DMF extraction. For the graft polymerization with gelatinized starch, the starch-water slurry was heated for 30 min at 85°C before reaction at room temperature with acrylonitrile and ceric ammonium nitrate. Saponifications in these experiments were carried out by stirring. 55 g of graft copolymer with 450 ml of 0.711 sodium hydroxide solution in a sigma mixer for 2 hr at 90-100°C. 

The biomaterial was dispersed in a definite amount of water. Ceric ammonium nitrate and nitric acid are then to be added slowly to the reaction mixture. Then, the monomer acrylic acid should be added drop wise to the reaction mixture. The reaction flask is to be placed in a water bath at 10-85°C for various time periods under stirring by a magnetic stirrer. After a definite time period, the reaction mixture is to be filtered and the homo-polymer should be removed with excess water. The grafted sample is to be dried to a constant weight and used for sorption studies. From the increase in weight of the biomaterial, the percentage of grafting should be calculated as follows ... 

A number of studies to determine the mechanisms of grafting onto collagen initiated by CAN, including characterization of the reaction products, have been reported (5, 8, 9, 53, 62). Ceric ammonium nitrate forms an effective redox system with alcohols, aldehydes, amines, and thiols. Alcohols form a ceric ion-alcohol complex, and the dissociation of this complex is the rate-determining step 63) ... 

Different types of chemical initiators such as FAS-KPS, benzoyl peroxide, azo-bis-iso-butylnitrile, H O, ascorbic acid-KPS, ammonium persulphate, ceric ammonium persulphate, ceric ammonium nitrate, etc., can be used for the graft copolymerization of various vinyl monomers such as methylacrylate, methyl methacrylate, acrylic acid, methacrylic acid, ethyl methacrylate, vinyl acetate, acrylamide, etc., onto polysaccharides [38-40]. Figure 2.1 shows the proposed mechanism through which the grafting can be explained [39]. 

B.S. Kaith, and A.S. Singha, "Some studies towards grafting of methylacrylate onto Flax fibre using ceric ammonium nitrate as redox initiator" Proceedings of the 4th International Petroleum Conference and Exhibition, New Delhi, 2001. 

Keywords Ceric ammonium nitrate, controlled drug release, flocculation, microwave assisted grafting, molecular programming, polysaccharide, SEM, intrinsic viscosity, rheology, drug delivery system... 

Another method of graft copolymer synthesis is a combination of microwave-based and conventional synthesis, i.e. using both microwave radiation as well as a chemical free radical initiator (e.g. ceric ammonium nitrate) together. This process is referred to as microwave assisted synthesis [47]. Although it yields a higher percentage grafting than the microwave initiated synthesis, the rehability of the synthesis process is low. 

Synthesis of the Graft Copolymer by Conventional Method (Using Ceric Ammonium Nitrate as a Free Radical Initiator)... 

Figure 5.3 Mechanism of ceric ammonium nitrate (CAN) initiated synthesis of polyacrylamide grafted carboxymethyl starch (CMS-g-PAM).

This oxidative cleavage of the C-2-C-3 bond can also be performed by using ceric ammonium nitrate (CAN), which produces an aldehyde group and a radical function on a carbon atom bearing a hydroxyl group. The resulting compound can then be polymerized with acrylonitrile to form cellulose-polyacrylonitrile graft copolymers (Fig. 31). 

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