After temperature treatment the polymer discs (0.2 g) were placed into deionized water (35 mL) for 48 h to remove non-crosslinked material. The water was exchanged every hour on the first day and every three hours on the next day. The swollen polymer discs were removed from the water, cut into small pieces and were dried in a vacuum oven for 48 h at 45 °C until weight constancy. To obtain the equilibrium water content, samples of 1 mg to 5 mg were placed into deionized water (2.5 mL) for 1h at ambient conditions. Subsequently, samples were removed, carefully wiped off with tissue paper to remove excess surface water and weighed (ms).