Novel hydrogels of chitosan and poly(vinyl alcohol)-g-glycolic acid copolymer with enhanced rheological properties

Poly(vinyl alcohol) (PVA) has been grafted with glycolic acid (GL), a biodegradable hydroxyl acid to yield modified poly(vinyl alcohol) (PVAGL). The formation of hydrogels at pH = 6.8 and physiological temperature through blending chitosan (CS) and PVAGL at different concentrations has been investigated. FTIR, DOSY NMR and oscillatory rheology measurements have been carried out on CS/PVAGL hydrogels and the results have been compared to those obtained for CS/PVA hydrogels prepared under the same conditions. The experimental results point to an increase in the number of interactions between chitosan and PVAGL in polymer hydrogels prepared with modified PVA. The resulting materials with enhanced elastic properties and thixotropic behavior are potential candidates to be employed as injectable materials for biomedical applications. © 2013 Elsevier Ltd.Peer Reviewe

Predicting miscibility in polymer blends using the Bagley plot: Blends with poly(ethylene oxide)

This paper explores the different methods currently available to obtain the partial solubility parameters of polymers in order to apply them for the prediction of miscibility in polymer/polymer blends. Blends based on poly(ethylene oxide) (PEO) have been chosen because its miscibility has been reported with a large number of polymeric counterparts (miscible or not), allowing the representation of its miscibility map with the required detail. The solubility parameters of PEO and 55 blending partners have been obtained using the most widely used group contribution (GC) methods, namely the ones proposed by Hoy, Hoftyzer-Van Krevelen, Stefanis-Panayiotou and Yamamoto (Y-MB), and have been used to build a Bagley plot. In addition, the miscibility map based on experimental data obtained from solubility tests has been also obtained and compared with the calculated ones. The clouds of points obtained around the point corresponding to PEO show different shapes, that can be used to obtain conclusions about the coherence and the accuracy of each of the different methods used to obtain the solubility parameters of polymers.The authors are thankful for funds from the Spanish Ministry of Innovation and Competitiveness MINECO (MAT2013-45559-P), the Basque Government, Department of Education, Universities and Research (GIC12/161-IT-632-13) and the European COST Action TD1305 - iPROMEDAI.Peer reviewe