Radiation-induced Transformations of Polymers in Aqueous Solutions
J.M. Rosiak, P. Ulanski, P. Kujawa, I. Janik, P. Stasica, S. Kadlubowski, M. Kozicki
Institute of Applied Radiation Chemistry, Technical University of Lodz Wroblewskiego 15, 93-590 Lodz, Poland
In this review, basic chemical processes occurring in aqueous polymer solutions under action of ionizing radiation are described first, followed by some examples of their practical applications and products so as: hydrogel wound dressing, drug delivery system, hybrid cell-polymer devices, polymeric material for intervertebral discs implant, gel dosimeter for radiotherapy, hydrogel-based dietary products, nano-and micro hydrogels. The action of ionizing radiation, either in the form of gamma rays or fast electrons, on polymers in dilute aqueous solutions occurs mainly through an indirect effect. Most part of the energy is absorbed by water. Ionization of water molecules and subsequent cascade of events leads in sub-nanosecond timescale to the formation of reactive species: hydroxyl radicals, hydrogen atoms and hydrated electrons. Those species react with macromolecules generating macroradicals, which undergo varies further transformations. Knowledge of the structure of macroradicals as well as mechanism and kinetics their reactions allows to control of the changes of properties polymers under irradiation. In some cases, the products with desired properties can be formed. Using of polymers (not monomers) as an initial materials usually allows avoid any additional purification of products, what is very important in case of numbers of medical applications. At least but not last, the formation and modification of the final products can be sometimes done during radiation sterilization step.