Multifunctional star-graft quarterpolymers PSn[P2VP-b-(PAA-g-PNIPAM)]n with a core-shell structure are used as the major component to fabricate layer-by-layer (LbL) microcapsules. The stars have a hydrophobic core and a dense thermal-responsive PNIPAM shell, therefore they can serve as nanocarriers for hydrophobic molecules, and at the same time, the PNIPAM shell enables their LbL assembly with another component, such as tannic acid used here. Due to the pH dependent protonation and deprotonation equilibrium of the P2VP and PAA blocks, the stars have different conformation and size at different pH conditions, the hydrogen bonding between the stars and tannic acid also depends on pH. As a result, the microcapsules have pH responsive structure and permeability: increase in solution pH leads to a decrease in the permeability and overall size of the microcapsules. On the other hand, with increasing temperature, the encapsulated hydrophobic molecules (Nile Red) have higher mobility, and tend to move out of the interior of the star polymers due to the change in hydrophobicity of the PNIPAM shell, and be release from the microcapsules. By combining the pH and temperature dual responsive property, a programmable and sequential release of hydrophobic and hydrophilic molecules from the core and shell of the microcapsules is successfully achieved.

Multi-compartmental polymeric microcapsules with dual-carrier and programmable release capabilities

251st National Meeting (2016)

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