Radicals gelatin

Bachman and coworkers (44), using ESR techniques, monitored the lifetime of free radicals in dry gelatin irradiated to approximately 50 kGy and stored in air at 20°C. Unlike the radicals in the gel, these are relatively immobile, and required several days to decay appreciably. Some were still detectable after about a month. The work and Friedberg and coworkers (45) indicates that the formation of these gelatin radicals in the dry state involves rupture of peptide bonds and that their decay does not involve combination of long chains. They found a decrease in the viscosity of solutions made from dry gelatin irradiated to a dose of 155 kGy. 

The free radicals initially formed are neutralized by the quinone stabilizers, temporarily delaying the cross-linking reaction between the styrene and the fumarate sites in the polyester polymer. This temporary induction period between catalysis and the change to a semisoHd gelatinous mass is referred to as gelation time and can be controUed precisely between 1—60 min by varying stabilizer and catalyst levels. 

Misra et al. have utilized the ceric-amine redox system for grafting MM A onto wool [60] and gelatin [61], The graft yield was explained in terms of basicity, nu-cleophilicity, and steric requirements of amines. A complex of ceric ion and amine (AH) decomposes to generate free radical species, which produce additional active sites onto the polymeric backbone where grafting can occur. 

The photochemistry of four triphenylmethane acid dyes was studied in poly(vinyl alcohol), methylcellulose and gelatin films. These model systems were chosen with a view to elucidating the complex free-radical reactions taking place in the heterogeneous dyed wool/ water/air system on exposure to UV radiation. The dye fading mechanism seems to involve an excited triplet state of the dye molecule [ 164] The rate of fading is governed by ... 

Mendis, E., Rajapakse, N., and Kim, S. K. (2005). Antioxidant properties of a radicals scavenging peptide purified from enzymatically prepared fish skin gelatin hydrolysate. ]. Agric. Food Chem. 53, 581-587. 

Nathan et al(Ref 1) examined a number of carbamic acid esters and concluded that the best stabilizing action on NC is obtd with compds in which at least one H atom is replaced by an aryl radical. Davis(Refs 2 5) examined several comps for their gelatinizing effect on NC Refs 1)F.L.Nathan et ai, BritP 12743(1912) CA 7, 3842(1913) 2)T.L.Davis, IEC 14, 1140 (1922) 3)Franklin(1935), lllff 4)Sidgewick, OrgChem of N(1937), 272 5)Davis(1943), 322... 

Water-immiscible monomers, or not more than slightly water-soluble monomers, may be polymerized as a suspension of large droplets in water. The droplets are kept in suspension by agitation and by the use of stabilizers, such as gelatin, talc, or bentonite clay. The free radical initiator used must be soluble in the monomer. Droplet size is 0.01-0.5 cm in diameter in typical operating modes. Polymerization in this way can be pictured as the simultaneous operation of many droplet-sized reactors, which on completion give beads, or pearls, of polymer. In fact these are the names, which are sometimes applied to this method of polymerization and to the product obtained. 

Natural polymers such as albumin, gelatin, fish glue, shellac, and gum arabic received attention up to the early 1900 s, after which time other materials such as bichromate, diazo compounds, iron salts, and silver halides were added to resins in order to hasten or accomplish their crosslinking. These systems were neither photopolymerization nor photocrosslinkable polymers. Instead, the added second component, when excited by light, produced a species which itself caused the formation of radical sites on a prepolymer or polymer chain which then led to cross-linking. 

Water soluble polymers behave like other solutes, i.e. radiation interacts with water principially and products of radiolysis react with the polymer. If the polymer is composed from different meres, what is the case with biopolymers, different segments of the polymer can have different rate constants of reaction with water derived radicals, c.f. the case of gelatin zols and gels [8], The radiation chemistry of polymers dissolved in water is the chemistry of reactions with OH, H, eaq, H2O2 and not, sensu stricto, of the polymer itself. Experiment shows clearly, that the radiation chemistry of the same polymer, but in the dry or almost dry state is completely different from radiation chemistry of its aqueous solution. Spurs are formed in the dry polymer and not in water. 

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