Fig. 7.

Temperature-responsive release of dye from a two-layer NIPA–DMAA capsule. Here, NIPA is the inner layer and DMAA is the outer layer. At 40 °C (above the LCST of NIPA), the pores in the inner NIPA layer are closed. In this case, the dye in the outer DMAA layer alone is released, as shown by the schematic. The corresponding micrograph shows a dark inner portion due to the turbidity of the NIPA layer, while the outer layer is transparent. At the 45 min mark, the temperature is lowered to ambient (25 °C). The pores in the NIPA layer open up, causing the inner dye to also release. This is shown by the schematic and in this case the entire capsule is transparent