Preparation of Layer-by-Layer Films with Remarkably Different pH-Stability and Release Properties Using Dual Responsive Block Copolymer Micelles

Layer-by-layer (LbL) films of micelles of poly[2-(dimethylamino)ethyl methacrylate]-b-poly[(2-(diethylamino)ethyl methacrylate)] (PDMA-b-PDEA) and poly(sodium 4-styrenesulfonate) (PSS) with remarkably different pH-stability and release properties are obtained via tuning film deposition conditions in a narrow pH and temperature range. Multilayers constructed at pH 8.5/25 degrees C or pH 8/30 degrees C completely disintegrate at physiologically related conditions, whereas film deposition at pH 8/25 degrees C produces stable films under the same conditions. Importantly, despite their stability, pH 8/25 degrees C multilayers release a considerable amount of pyrene at moderately acidic pH due to disintegration of the micellar cores. The amount of pyrene increases significantly at body temperature due to lower critical solution temperature (LCST)-type phase behavior of PDMA coronal chains. The difference in properties of multilayers is explained by the extent of association among the layers which can be tuned by film deposition conditions in a narrow pH and temperature range due to dual responsive, that is, pH and temperature behavior of PDMA-b-PDEA micelles