Smart Materials

I. Tailoring Stimuli Sensitive Polymeric Materials

II. Composites of Responsive Polymer Microgels & Inorganic Oxide Nanoparticles

Composites consisting of inorganic materials dispersed within a polymeric framework offer a versatile avenue to tailor the functional properties of materials. To design advanced functional materials for photocatalysis and other applications, we have focused on composite materials of inorganic nanoparticles such as TiO2 embedded within microspheres of a responsive polymeric network.

These composites are promising candidates for applications such as wastewater remediation where use of nanoparticles of TiO₂ is advantageous for photocatalysis but separation of the nanoparticles is relatively difficult. In composite form, gravity settling behavior of the particles can be a promising characteristic in wastewater remediation as it allows for an easy recovery mechanism.

· C. A. Coutinho, R. Harrinauth and V. K. Gupta, “Settling Characteristics of Composites of PNIPAM Microgels and TiO₂ Nanoparticles”, Colloid and Surfaces A: Physicochemical and Engineering Aspects (Under Review).

· C. A. Coutinho and V. K. Gupta, “Formation and Properties of Composites Based on Microgels of a Responsive Polymer and TiO₂ Nanoparticles”, Journal of Colloid and Interface Science (In Press).

Titania nanoparticles remain suspended in water after degradation of a dye by radiation with a fluorescent BLB tubelight (~360nm)

Composite particles accomplish the same extent of degradation of the dye but settle rapidly leaving clear liquid on top.

Our research group is working with polymers that are optically or thermally responsive. These materials exhibit reversible changes in physical and chemical properties in response to various stimulus.

One of the polymers that we use exhibits reversible coil to globule transition with change in temperature. This in turn causes changes in shape and other physical properties. Another material that we have focused on is a synthetic rod-like polypeptide. The goal of our studies is to enhance the optical properties of these polymeric materials by combination with photochromic moieties or metallic nanoparticles that have unique optical properties. Ongoing research in the group focuses on understanding the interplay between the structure of these novel materials and their optical properties (for example, absorbance, swelling, deswelling, dipole moment) as a function of the environmental stimulus.

Establishment of these structure-property relationships will form the basis for exploiting these unique polymers in advanced applications such as actuators, drug delivery, separations, energy transduction, and catalysis.

· Mun-Sik Kang and Vinay K. Gupta, "Photochromic Cross-links in Thermo-responsive Hydrogels of Poly(N-isopropylacrylamide): Enthalpic and Entropic Consequences on Swelling Behavior”, J. Physical Chemistry B, 106, 4127-4132 (2002).

· Dennis W. Smithenry, Mun-Sik Kang, and Vinay K. Gupta, "Telechelic Poly(N-isopropylacrylamide): Polymerization and Chain Aggregation in Solution”, Macromolecules, 34, 8503-8511 (2001).

· Alveda J. Williams and Vinay K. Gupta, "Role of Photochromic Initiator in the Synthesis and Physical Properties of Hinged, Photoresponsive Polypeptides”, J. Polymer Science: Part B Physics, 39, 2759 - 2773 (2001).