Poly irradiating effect

Fig. 29. Recovery of absorbance in irradiated poly U effected by combinations of thermal and short wavelength treatment (Swenson and Setlow48).

Hausberger, A. G., Kenley, R. A., and DeLuca, P. P. Gamma irradiation effects on molecular weight and in vitro degradation of poly(D,L-lactide-CO-glycolide) microparticles. Pharm. Res. 12(6) 851—856, 1995. 

Montanari, L., Costantini, M., et al. Gamma irradiation effects on poly(DL-lactictide-coglycolide) microspheres. J. Contr. Rel. 56(1—3) 219-229, 1998. 

L14. Lehrer, S. S., and Fasman, G. D., Ultraviolet irradiation effects in poly-L-tyrosine and model compounds. Identification of bityrosine as a photoproduct. Biochemistry 6, 757-767 (1967). 

Montanari L, Cilurzo F, Valvo L, et al. Gamma irradiation effects on stabibty of poly(lactide-co-glycolide) microspheres containing clonazepam. J Control Release 2001 75(3) 317-330. 

Nguyen and Kausch [1984] found that the presence of phenyl groups in poly(styrene-co-acrylo-nitrile), SAN, protects PMMA in the blend, during radiolysis (Table 11.9). SAN and PMMA were dissolved in dimethyl formamide, 50- J,m-thick films were cast, and then dried under vacuum. Transparent bar specimens were compression-molded from the film. Mixing the polymers by co-precipitation from methanol resulted in opaque samples. Gamma irradiations were done in evacuated and sealed glass tubes, at a dose rate of 3 kGy/h. Comparison of freshly irradiated samples with irradiated and annealed ones showed the absence of any post-irradiation effects. 

Finally, a few articles have appeared on chemiluminescence of polymers. This technique has been used to detect hydroxy radicals in wood oxidation,y-irradiation effects on polyethylene, oxidation of nitrile-butadiene rubber, rubber under stress,antioxidant efficiencies in polyethylene, reactions of peroxy radicals, stereoregularity in poly(propylene), colour development in epoxy resins and structural changes in thermally aged poly(phenylene sulfide). ... 

Burillo, G., Tenorio, L., Bueio, E., Adem, E., Ixrpez, G.P. Electron beam irradiation effects on poly(ethylene terephtalate). Radiat Phys. Chem. 76, 1728-1731 (2007)... 

Han, S.O., Cho, D., Park, W.H., and Drzal, L.T. (2006) Henequen/ poly(butylene succinate) biocomposites electron beam irradiation effects on henequen fiber and the interfacial properties of biocomposites. Compos. Interfaces, 13, 231-247. 

A1 Ani, K.E., Ramadhan, A.E., Anabtawi, M. Irradiation effect on stability of plasticized poly(fluorostyrene) isomers in solution. Int J. Photochem. (2014). Article ID 536068... 

Heat stabilizers protect polymers from the chemical degrading effects of heat or uv irradiation. These additives include a wide variety of chemical substances, ranging from purely organic chemicals to metallic soaps to complex organometaUic compounds. By far the most common polymer requiring the use of heat stabilizers is poly(vinyl chloride) (PVC). However, copolymers of PVC, chlorinated poly(vinyl chloride) (CPVC), poly(vinyhdene chloride) (PVDC), and chlorinated polyethylene (CPE), also benefit from this technology. Without the use of heat stabilizers, PVC could not be the widely used polymer that it is, with worldwide production of nearly 16 million metric tons in 1991 alone (see Vinyl polymers). 

The most innovative photohalogenation technology developed in the latter twentieth century is that for purposes of photochlorination of poly(vinyl chloride) (PVC). More highly chlorinated products of improved thermal stabiUty, fire resistance, and rigidity are obtained. In production, the stepwise chlorination may be effected in Hquid chlorine which serves both as solvent for the polymer and reagent (46). A soHd-state process has also been devised in which a bed of microparticulate PVC is fluidized with CI2 gas and simultaneously irradiated (47). In both cases the reaction proceeds, counterintuitively, to introduce Cl exclusively at unchlorinated carbon atoms on the polymer backbone. 

Maleimides Alkyl and aryl maleimides in small concentrations, e.g., 5-10 wt% significantly enhance yield of cross-link for y-irradiated (in vacuo) NR, cw-l,4-polyisoprene, poly(styrene-co-butadiene) rubber, and polychloroprene rubber. A-phenyhnaleimide and m-phenylene dimaleimide have been found to be most effective. The solubihty of the maleimides in the polymer matrix, reactivity of the double bond and the influence of substituent groups also affect the cross-fink promoting ability of these promoters [82]. The mechanism for the cross-link promotion of maleimides is considered to be the copolymerization of the rubber via its unsaturations with the maleimide molecules initiated by radicals and, in particular, by allyfic radicals produced during the radiolysis of the elastomer. Maleimides have also been found to increase the rate of cross-linking in saturated polymers like PE and poly vinylacetate [33]. 

Temperature dependence (related to the temperature dependence of the conformational structure and the morphology of polymers) of the radiation effect on various fluoropolymers e.g., poly (tetrafluoroethylene-co-hexafluoropropylene), poly(tetrafluoroethylene-co-perfluoroalkylvinylether), and poly(tetrafluoroethylene-co-ethylene) copolymers has been reported by Tabata [419]. Hill et al. [420] have investigated the effect of environment and temperature on the radiolysis of FEP. While the irradiation is carried out at temperatures above the glass transition temperature of FEP, cross-linking reactions predominate over chain scission or degradation. Forsythe et al. [421]... 

Several approaches have been undertaken to construct redox active polymermodified electrodes containing such rhodium complexes as mediators. Beley [70] and Cosnier [71] used the electropolymerization of pyrrole-linked rhodium complexes for their fixation at the electrode surface. An effective system for the formation of 1,4-NADH from NAD+ applied a poly-Rh(terpy-py)2 + (terpy = terpyridine py = pyrrole) modified reticulated vitreous carbon electrode [70]. In the presence of liver alcohol dehydrogenase as production enzyme, cyclohexanone was transformed to cyclohexanol with a turnover number of 113 in 31 h. However, the current efficiency was rather small. The films which are obtained by electropolymerization of the pyrrole-linked rhodium complexes do not swell. Therefore, the reaction between the substrate, for example NAD+, and the reduced redox catalyst mostly takes place at the film/solution interface. To obtain a water-swellable film, which allows the easy penetration of the substrate into the film and thus renders the reaction layer larger, we used a different approach. Water-soluble copolymers of substituted vinylbipyridine rhodium complexes with N-vinylpyrrolidone, like 11 and 12, were synthesized chemically and then fixed to the surface of a graphite electrode by /-irradiation. The polymer films obtained swell very well in aqueous... 

While "conventional positive photoresists" are sensitive, high-resolution materials, they are essentially opaque to radiation below 300 nm. This has led researchers to examine alternate chemistry for deep-UV applications. Examples of deep-UV sensitive dissolution inhibitors include aliphatic diazoketones (61-64) and nitrobenzyl esters (65). Certain onium salts have also recently been shown to be effective inhibitors for phenolic resins (66). A novel e-beam sensitive dissolution inhibition resist was designed by Bowden, et al a (67) based on the use of a novolac resin with a poly(olefin sulfone) dissolution inhibitor. The aqueous, base-soluble novolac is rendered less soluble via addition of -10 wt % poly(2-methyl pentene-1 sulfone)(PMPS). Irradiation causes main chain scission of PMPS followed by depolymerization to volatile monomers (68). The dissolution inhibitor is thus effectively "vaporized", restoring solubility in aqueous base to the irradiated portions of the resist. Alternate resist systems based on this chemistry have also been reported (69,70). 

During photolysis, the double bond content of the polysilane(P-l)(15mol% in this experiment) decreased to 10mol%, as measured by 1H-NMR spectroscopy. However, the ratio, quantum yield of scission(Q(S))/quantum yield of crosslinking(Q(X)), was not affected by the reaction of the double bond. West and his coworkers have reported that poly((2-(3-cyclohexenyl)-ethyl)methylsilane-co-methylphenylsilane) crosslinked upon irradiation(55). The difference between our results and West s may lie in the amount of the double bond and inhibitation of the radical closslinking by the phenol moiety. Polysilane with a halogen moiety, P-8, photodecomposed rapidly, compared with P-1 or P-3. The introduction of a chloride moiety was effective for the sensitization of the photodegradation. Similar results has already been reported(55). 

Recent studies on LET effects In 2 mm thick samples of polymers have shown no difference between fast neutron and Co60 gamma irradiations for poly(olefIns) (32), a small difference for... 

The high photostability and acute fluorescence intensity are two major features of DDSNs compared to dye molecules in a bulk solution. The early DDSN studies have focused on these two properties [8, 13]. For example, Santra et al. studied the photostability of the Ru(bpy)32+ doped silica nanoparticles. In aqueous suspensions, the Ru(bpy)32+ doped silica nanoparticles exhibited a very good photostability. Irradiated by a 150 W Xenon lamp for an hour, there was no noticeable decrease in the fluorescence intensity of suspended Ru(bpy)32+ doped silica nanoparticles, while obvious photobleaching was observed for the pure Ru(bpy)32+ and R6G molecules. To eliminate the effect from Brownian motion, the authors doped both pure Ru(bpy)32+ and Ru(bpy)32+-doped silica nanoparticles into poly(methyl methacrylate). Under such conditions, both the pure Ru(bpy)32+ and Ru(bpy)32+ doped silica nanoparticles were bleached. However, the photobleaching of pure Ru(bpy)32+ was more severe than that of the Ru(bpy)32+ doped silica nanoparticles. 

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