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Semi-interpenetrated network with improved sensitivity based on poly(N-isopropylacrylamide) and poly(aspartic acid)



Dual-sensitive semi-interpenetrated (sIPN) hydrogel structure was prepared by including poly(aspartic acid) (PAS) chains into the thermosensitive poly(N-isopropyl acrylamide) (pNIPAM) polymeric network during its preparation. The new hydrogels have been characterized from the viewpoint of swelling behavior in different environment conditions, as well as by FT-IR analysis, scanning electron microscopy, and thermal analysis. According to the key morphological aspects, the pNIPAM network presents homogenous pore distribution with honeycomb shape and pore dimension between 50 and 150 μm. The PAS chains inclusion leads to a drastic reduction of the pore size and increasing of the polymeric area contact with the environment attesting as well the intimate connection among the polymeric chains with physical links between them. The thermal analysis evidenced a decrease of the maximum temperature decomposition and the increase of residual mass of hydrogels proportional with the increase of the PAS amount. The prepared sIPN polymeric networks exhibit different swelling behavior related to their composition. The pH sensitivity brought by the PAS partner offers the advantage of using the sIPN network for medical applications, where this kind of polymer system can release the drug molecules to a different level of the human body. The performed tests highlighted the sensitivity of the prepared gels by changing their properties under the variation of environmental conditions, with respect to temperature and pH. Thereby, the synthesized gels have tailored properties to be used as sensitive structures. POLYM. ENG. SCI., 53:2345–2352, 2013. © 2013 Society of Plastics Engineers