Thermal transitions of benzene in a poly(ethyl acrylate) network

The thermal transitions observed in hydrogels are usually explained by the existence of different states of water such as `bound' and `free'. In this work a polymer network is swollen with a non-polar solvent and some of the most characteristic features of its thermograms, such as the existence of an amount of non-crystallizable solvent, are compared with those of water in a hydrogel. A poly(ethyl acrylate) network was swollen with different benzene contents and subjected to cooling and heating scans in a differential scanning calorimeter. Three qualitatively different kinds of thermograms are found, depending on the benzene content in the polymer network, which are analysed according to a phase diagram where the temperature of the transitions is plotted versus composition.