Thewarm solutionwas cast onto a polymethyl methacrylate
plate and oven-dried at 50 C for 8 h. After completely cooling at
room temperature, the film was peeled from the polymethyl
methacrylate plate and balanced at 25 C and 53% RH by placing in a
cabinet over a saturated Mg(NO3)2 solution for at least for 5 days
prior to analysis. The film prepared with NS was used as control.