The solutions(∼30 mL) were spread with an Elcometer 3545 adjustable film applicator with the gap set at 200m and were allowed to dry in a climate test chamber (environmental test chamber for constant climate Binder KMF 115 GmbH,Germany),at 40 ◦C and relative humidity(R.H.) =30%, for 2–3h.Finally,the films were peeled off from the supports and stored in plastic bags.