Samanvaya Srivastava, Institute for Molecular Engineering/University of Chicago
November 3, 2016
11:00 AM - 12:00 PM
810 S. Clinton Street, Chicago, IL 60612
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Complexation Driven Assembly of Block Copolyelectrolytes
Hosted by: Vivek Sharma
Block copolymer amphiphiles, driven by solvophobic interactions, assemble into a range of micellar structures. Similar spherical micellar assemblies of block copolyelectrolytes can also be achieved by relying on electrostatic interactions between oppositely charged polyelectrolytes. These electrostatics driven assemblies, comprising polyelectrolyte complex cores and neutral coronae, maintain a large fraction of water in their cores, thus making them particularly useful for encapsulation and delivery of charged therapeutics and nucleotides.
The generic micelle structures in complexation driven assemblies have been understood to be similar to those of amphiphilic micelles. However, recent investigations have unveiled salient differences between these solvophobicity- and electrostatics-driven assemblies. This presentation will highlight these differences by elaborating on both the typically acknowledged structure-defining contributions (via complexation) and additional structure-directing contributions (via intra-chain repulsion) of the charged blocks. Relying on extensive structural characterization from X-ray and neutron scattering experiments, specific examples of assembly of model oppositely charged diblock and triblock copolyelectrolytes that form spherical micelles and unique inter-connected gels, respectively, will be discussed. Further, the networks, at low polymer concentrations, phase separate from the solution, and our hypothesis on their structural features being primarily dictated by the conformations of the neutral block will be argued. In addition, conclusions from molecular dynamics simulations on the driving forces behind these unique assemblies and their direct comparisons with corresponding amphiphilic assemblies will be presented.
About the Speaker:
Samanvaya Srivastava received his Ph. D. from Cornell University in 2014. His doctoral dissertation research under the supervision of Prof. Lynden A. Archer was focused on structure and properties of nanoparticle dispersions. Samanvaya developed strategies for achieving uniform nanoparticle dispersion in polymeric matrices and the effects of particle distribution on bulk properties in nanocomposites. Prior to this, he received his B. Tech. and M. Tech. degrees in Chemical Engineering from Indian Institute of Technology Kanpur. In his Masters research, conducted under the guidance of Prof. Ashutosh Sharma, he elucidated the role of physical heterogeneities on substrate surfaces as manifested in the electric force induced patterns in thin polymer films.
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