2007 International Nuclear Atlantic Conference - INAC 2007 Santos, SP, Brazil, September 30 to October 5, 2007 ASSOCIAÇÃO BRASILEIRA DE ENERGIA NUCLEAR - ABEN ISBN: 978-85-99141-02-1 EFFECTS OF STERILIZATION ON POLY(VINYL ALCOHOL) (PVAl) HYDROGELS MATRICES Maria José A. Oliveira, Kiriaki M. S. Rodrigues, Duclerc F. Parra, Ademar B. Lugão Instituto de Pesquisas Energéticas e Nucleares (IPEN / CNEN - SP) Av. Professor Lineu Prestes 2242 05508-900 São Paulo, SP mariajhho@yahoo.com.br ABSTRACT The poly(vinyl alcohol) (PVAl) is a polymer of great interest for new materials development due to its specific characteristics particularly for biomedical applications. PVAl with polyethylene glycol (PEG) 300 was processed using freezing-thawing sequence of thermal cycles for hydrogel preparation. The samples were evaluated by gel fraction (%), water uptake (%) and thermogravimetry analysis (TGA). The hydrogel was sterilized under ionizing radiation from Cobalt-60 source at 25 kGy dose and the effects of the radiation on the hydrogel properties was discussed in this work. The results of swelling, gel fraction and thermal stability are in part influenced by the sterilization method. The presence of PEG in PVAl hydrogels forms less dense hydrogels under freeze/thawing cycles. The swelling in the sterilized hydrogels is higher than the not sterilized hydrogel in consequence of chain scissions in the polymeric structure due to the radiation process. 1. INTRODUCTION The current study of the polymeric science considers the biomedicine as one of the most important areas for application of modified polymeric structures as new materials. An example, is the poly(vinyl alcohol) (PVAl), a polymer of great interest due to its specific characteristics for biomedical applications. The synthesis of the modified polymeric hydrogel of PVAl with polyethylene glycol (PEG) 300 was processed using freezing-thawing known as sequence of thermal cycles. PVAl is a water-soluble polymer employed in practical applications due to its excellent chemical resistance, processing properties, biodegradability and physical properties [1, 2]. The presence of a second polymer can performs significant change in the overall crystalline structure of the hydrogel. Softening PVAl hydrogel could be obtained with crosslink of PVAl in the presence of PEG. Morphological changes can lead to different performance of the hydrogel and the characteristics of swelling degree and diffusional behavior may change under physiological stimuli [3] representing an important feature for controlling release of bioactive species. Parameters affecting the final properties of PVAl gels prepared by freeze/thaw cycling include those that describe the starting materials (degree of substitution, tacticity) and those that define the processing steps (solution concentration, number of both the freezing and thawing steps). Despite the intense study there is a little understanding of how freeze/thaw cycling actually enhances gelation and whether the final gels microstructure depends significantly on the cycling protocol selected [1]. Many related and possibly relevant studies