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We are working in the interdisciplinary area of research involving polymer chemistry, supramolecular chemistry and biomedical science. Primarily we engineer molecules or macromolecules by specific functionality to realize precision assembly over different length scales and explore them for functions in biomedical and material science. Recent research activity of our group may be classified under the following three broad areas:
- Engineered Amphiphiles (Small Molecule and Macromolecule): We have developed new class of supramolecularly engineered amphiphilic macromolecules (SEAM) which consist of a supramolecular structure directing unit (SSDU) in the terminal of a hydrophilic polymer/ protein. Specific supramolecular assembly motif of the SSDU (consisting of a H-bonding group and a naphthalene-diimide (NDI) chromophore) regulates the entropy-driven remarkably stable aqueous self-assembly of polymers and/ or proteins by superseding the packing parameters. By this strategy we have pinned down the resolution of structure controlling parameters to molecular level which opens up numerous opportunities for controllable mesoscopic structure formation of synthetic macromolecule with molecular scale precision. Such SSDU appended small molecule amphiphiles exhibit highly stable self-assembled nanostructures, controls the surface functional group display and thus enables promising biological applications, including multivalent binding with protein, enzyme inhibition, and antimicrobial activity and so on. We have recently demonstrated the utility of such chromophore appended amphiphilic assemblies for redox responsive disassembly.
- Stimuli Responsive Amphiphilic Polymers for Biomedical Application: We have established a condensation polymerization methodology for synthesis of telechelic degradable polymers having pH-responsive β-thiopropionate ester or glutathione responsive disulfide group in the backbone and functional chain-ends. We are working on wide-ranging biocompatible amphiphilic polymers using these degradable scaffolds with specific emphasis on aqueous self-assembly, dynamics (using FRET), drug encapsulation efficacy and pH/ glutathione-responsive drug release in vitro to cancer cells which show highly promising results. We have recently explored covalent bioconjugates using such degradable scaffolds which are encoded with information for triggered cascade degradation for targeted drug delivery application. The newly developed methodology for poly(disulfides) is unique and offer exciting new opportunities for functional biomaterials using this classical polymeric scaffold.
- H-bonding Driven Supramolecular Polymerization of Aromatic Donor (D) and Acceptor (A) Monomers: We have extensively studied H-bonding driven supramolecular polymerization (SP) of various D+A, D-π-A and D-σ-A type systems and developed an in-depth understanding on the structural nuances and chirality on the development of internal order, mode of stacking (alternating/ segregated); and the thermodynamics and mechanistic aspects (cooperative/ isodesmic) supramolecular organization. We have successfully correlated these molecular assembly features with the mesoscopic structure (micelle, gel, vesicle and chromonic mesophase) and photophysical properties (luminescence, charge-transport and excited state dynamics). Very recently we have explored the pathway diversity in such complex molecular assemblies and established new methodologies for controlled supramolecular polymerization by chain growth mechanism using external trigger (light) or seed or other molecular entities as the initiating species to synthesize supramolecular polymers and copolymers of multiple building blocks in sequential fashion with structural precision over different length scales that are ubiquitous in biological systems. In an effort to combine the advantages of supramolecular (precise internal order) and covalent polymers (stability), our group has recognized intra-chain H-bonding driven folding followed by macroscopic assembly of chromophore-appended polyurethane as an attractive scaffold for constructing semiconducting organic nanotubes with percolated pathway for highly efficient charge-transport.