Kinetics of radiation

III. KINETICS OF RADIATION-INDUCED POLYMERIZATION OF ACRYLAMIDE IN AQUEOUS SOLUTION... 

The kinetics of radiation-initiated polymerizations follow in a relatively straightforward manner those of photolytic polymerization. The initiation rate is determined by the radiation intensity and the concentration and susceptibility of the compound that radiolyzes to yield the initiating species (ionic and/or radical). The final expression for Rp is determined by the exact details of the initiation, propagation, and termination steps. 

There is a sequence of experimental techniques ranging from the open beaker on the bench to the extremely rigorous h.v.t. used for studying the kinetics of radiation-induced cationic polymerisations. Each technique in the series has its characteristic level of extraneous materials, and as the level of cleanliness is raised, there is a concurrent loss of flexibility. 

The most important feature of ionizing radiations is, as the term implies, ionization to give ionic intermediates in irradiated systems. Though radiation-induced radical polymerization had long been studied, it is only a decade since radiation-induced ionic polymerization was first found. In 1957, Davison et al. obtained polymer from isobutene, which is known not to be polymerized by radical catalysts, by irradiating at low temperature with y-rays (7). Before long, the radiation-induced polymerization of styrene was proved to proceed as an ionic mechanism in suitable solvents (2,3,4). Since these pioneering researches, the study of the chemical kinetics of radiation-induced ionic polymerization has been extended to several vinyl, diene and cyclic monomers. 

The kinetics of radiation-induced polymerization of bulk nitroethylene was also studied at 10° C by the use of hydrogen bromide as an anion scavenger (27). The value of Gt (yield of the initiation by 100 eV energy absorbed) was found to be about 3, which was much larger than the value obtained for many radiation-induced cationic polymerizations. The propagation rate constant, kp, was estimated to be 4 x 107 M-1 sec-1. The large kp value was attributed to the concept that the propagating chain ends were free ions in contrast to the existence of counter ions in catalytic polymerization. 

Finally, various attempts have been reported to interpret the kinetics of radiation grafting. The study by Mock, and Vanderkooi (123) concerned the mutual radiation grafting of styrene from the vapor phase to ethyl cellulose film at 50° C. The radical flux was determined separately using electron spin resonance. The kinetic scheme rigorously took account of the diffusion controlled nature of the reaction and the appropriate diffusion constants were separately determined (124). The value for the ratio of for the graft polymerization was determined as... 

S. Ya. Pshezhetskii, Mechanism and Kinetics of Radiation-Chemical Reactions. Khimiya, Moscow, 1968 (in Russian). 

Einstein s derivation of the black-body radiation law is particularly important, for it gives us an insight into the kinetics of radiation processes. Being a kinetic method, it can be used even when we do not have thermal equilibrium. Thus if we know that radiation of a certain intensity is falling on atoms, we can find how many will be raised to the excited state per second, in terms of the coefficient Bn. But this means that we can find the absorptivity of matter made of these atoms, at this particular wave length. Conversely, from measurements of absorptivity, we can deduce experimental values of Bn. And from Eq. (2.8) we can find the rate of emission, or the emissive power, if we know the absorptiv-... 

Keene JP. (1960) Kinetics of radiation-induced chemical reactions. Nature 188 843-844. 

The first coupling of a LINAC with infrared spectroscopy has been performed by Palmese et al. in order to study in situ kinetics of radiation-induced cationic polymerization of epoxy systems. The aim of the study is to understand the curing behavior of polymers under irradiation. A UV light source and an electron beam (10 MeV pulse width of the beam from 2.5 to 10 pm) are coupled to a portable near infrared (NIR) instrument. Briefly, a portable NIR spectrometer (Control Development Incorporated, South Bend, IN, USA) is used,... 

Trummer M, Nilsson S, Jonsson M. (2008) On the effects of fission product noble metal inclusions on the kinetics of radiation induced dissolution of spent nuclear fuel. J Nucl Mater 378 55-59. 

The kinetics of radiation induced polymerization in solution in which energy transfer is operative have been developed by Nikitina and Bagdassarian (3). A term was introduced, P representing the relative probability of energy transfer from fi to S /ersus transfer from S to M. This leads to a modified expression... 

Principal methods of investigations of the kinetics of radiation-induced polymerization include ... 

In the analysis of the kinetics of radiation-induced polymerization in solution, the ratios of the polymerization rates in solution vs and in bulk vb determined experimentally have the following dependence on the molar fraction of the monomer [M] ... 

Schmidt. K. H., Electrical conductivity techniques for studying the kinetics of radiation induced chemical reactions in aqueous solutions. Int. I. Radiat. Phys. Chem. 4, 439 (1972). 

Fang, Y, Shi, T., Wang, W. et al. 1989. Kinetics of radiation-induced graft copolymerization of 2-hydroxyethyl methacrylate onto polyethylene membranes. J Appl Polym Sci. 38 821-828. 

Zaikina, R.F., Zaikin, Y.A., and Nadirov, N.K. 1997. Mechanisms and kinetics of radiation-induced thermal cracking of heavy oil fractions. Oil and Gas, Kazakhstan 2 83-100. 

Jones GDD, O NeiU P. Kinetics of radiation-induced strand break formation in single-stranded pyrimidine polynucleotides in the presence and absence of oxygen a time-resolved light-scattering study. Int J Radiat Biol. 1991 59 1127-1145. 

Two types of analytical methods are currently used to study the kinetics of radiation curing ... 

IR Study of the Deprotection Kinetics of Radiation-Exposed Resist Films Upon exposure to UV-radiation, the PAG decomposes with a rate constant kc to produce the photoacid (designated as Acid), as illustrated in equation 1. Here hv represents photon energy, where h is the Planck s constant and v is the frequency of the radiation. 

G. Wenz, G. Wegner. Kinetics of Radiation Induced Polymerization of a Diacetylene Studied by Analysis of the Molecular Weight Distribution. Mol. Cryst. Liq. Cryst. 9i (1983) 99... 

El-Gendy, E. H. Ali, N. M. Marie, M. M. El-Shanshoury, 1. A. Dyeing kinetics of radiation-grafted polyester fabric using different dyes. Indian J. Fibre Text. Res. 2007, 32, 232-240. 

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