Polymer Capsules: Fundamental Studies and New Concepts

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Tiwari, Khyati R
Raghavan, Srinivasa
Polymer capsules and beads can be easily created by combining either two oppositely charged polymers or one polymer and a multivalent salt. These structures have been mainly investigated until now for their controlled release properties. Here, we study the ability to impart new functionalities to capsules by embedding a second kind of colloidal or nano-structure in their interior. Three different concepts are explored in this regard. First, we demonstrate capsules that are responsive to pH. For this purpose, we entrap vesicles made from a diacetylene surfactant in chitosan capsules. The resulting capsules change their color blue blue to red as the pH of the solution is increased. The next concept involves capsules with the ability to sense and separate cations from solution. In this case, nanoscale particles of synthetic clay (laponite) are localized in alginate beads. The resulting hybrid beads can effectively separate a cationic dye from a mixture of cationic and anionic dyes. The third concept involves linking of magnetic chitosan-gelatin capsules in a chain to create an artificial earthworm, i.e., a structure that can undergo guided motion in a fluid environment under an external magnetic field.