TIFR
Department of Chemical Sciences
School of Natural Sciences

October 21, 2016 at 2.30 pm. in AG-66

Title :

Design and Synthesis of Polymeric Materials: Structure-Property Relationship via Self-assembly and Biomedical Applications

Abstract :

Design and validation of pericyclic reactions for sensing conformational stretching in polymer materials.

The naphthalene and anthraquinone based fluorescent reporter molecules were synthesized in multistep for monitoring pericyclic reactions in polymers. These reporter molecules were incorporated into polymer backbones by click reactions. The reaction was monitored optically and optimized using organic chemistry characterization techniques. The mechanical force felicitate to bonds to come into proper orientation for claisen reaction to occur. The overall goal of the research is to design, implement, and validate functional groups designed to react specifically within stressed polymer materials to signal the onset of mechanical failure.

 

Design and synthesis of Novel Alternating sulfone copolymers for biomedical applications

Interest in stimulus-responsive polymers and materials has been increasing in recent years. In particular, efforts to apply these polymers for biomedical applications have focused on changing the structure of assemblies and particles in response to both endogenous molecules and externally-applied energy sources to release drugs, activate contrast agents, or initiate fluorescent signal. Sulfur dioxide has been shown to copolymerize with certain vinyl monomers in a specifically alternating manner, provided that the vinyl group is immediately adjacent to an electron-donating group; examples include vinyl acetate, vinyl carbonate, and olefins. The resulting copolymer possesses a low ceiling temperature. The depolymerisation of poly(vinyl acetate-alt- sulfur dioxide) as initiated by chemical stimuli such as reactive oxygen species (ROS) and mechanical stimuli was studied as a proof of concept. Then, a novel class of hydrolytically depolymerizable macromolecules, poly(O-vinyl carbamate-alt-sulfones), were synthesized via free radical polymerization with excellent functional group tolerance. The polymers were then found to form nanoparticles capable of encapsulating both Rhodamine B and Alexa Fluor 488, and the resulting particles were labile at pH > 6. Finally, these particles were found to retain their contents in mucus at pH 5 but release it at pH 8, resulting in an increase in diffusivity of encapsulated fluorophores from very small to matching that of free dye. Current efforts are focused on adapting the polymers and their particles for mucosal drug delivery.

 

During doctoral studies, my research focussed on the self assembling behavior of various pyrene labeled polymers having different architecture like homopolymers, block, and random copolymers, where the pyrene labeling was varied from 1-100%. The photophysical properties were studied using various fluorescence techniques like steady-state and life time decay analysis as well as time resolved emission spectra (TRES). The applicative aspect of the pyrene labeled polymers was also shown by rhodamine dye encapsulation and release studies as a function of temperature and its temperature triggered release was also used as a handle to understand the microstructural changes inside the polymer microcapsule.

 

Thus, the thesis analyses the following important aspects:

 

1.    Exploration of fundamental aspects of the self assembly of different pyrene labelled polymers like block, random or homopolymers by the detailed photophysical analyses

 

2.    Applicative aspects of the pyrene labeled polymers: probed by rhodamine B encapsulation and release.

 

3.    Self assembly behavior in H-bonded versus non-H-bonded polymers at very dilute concentrations: differences and similarities.

 

 4.       Architectural differences among the polymers: probed by TRES and temperature dependent fluorescence.