ChE Seminar: Molecular engineering of salt-containing polymer photoresists and electroactive membranes

Details

Fernando Escobedo, Ph.D.
Samuel W. and Diane M. Bodman Professor
Chemical and Biomolecular Engineering
Cornell University

Title: Molecular engineering of salt-containing polymer photoresists and electroactive membranes

Abstract: Many important soft materials being used or developed for technological applications involve mixtures of polymers and ionic salts in the dry state, e.g., for solid electrolyte membranes in batteries, sensors, separators, etc. The connection between molecular interactions, micro-structure and properties of such mixtures is not fully understood; in this work we probe this connection using atomistic simulations to study two model systems, one involving photoresists and the other dual-conducting polymers.

In the first case we are interested in photoresists suitable for extreme-UV (EUV) lithography, one of the most promising routes for fabrication of microchips with sub 10 nm feature sizes. Typical formulations contain a polymer base, a photoacid generator (PAG) and a quencher, the latter two being ionic salts assumed to disperse homogeneously in the host polymer. Our study, which focuses on the pre-EUV exposure system, shows that PAGs tend to form small aggregates whose size and shape depend on the chemistry of the base polymer and can affect the roughness of the features developed post exposure. We demonstrate a computational framework that allows an efficient discrimination of candidate polymer-PAG chemistries that are conducive to suitable dispersibility.

The second vignette concerns the design of a single soft material capable of conducting both ions and electrons, as an ideal membrane for applications that entail interfacing biological systems (where ions are the signal carriers) and electronic systems (where electrons are the signal carriers). Through both modeling and experiments, we demonstrate how both small tri-block oligomers and side-chain copolymer based on thiophene, ethylene-oxide, and dopant Li-salts, as model conducting units can be designed to form morphologies with percolating channels to achieve such dual conductivity. We then demonstrate how simulations can be used to correlate ionic conductivity with the microstructure of the ion solvation shell and to explore how different chemistries can be used to improve ionic conductivity.

Bio: Professor Fernando Escobedo received a B.S. degree in Chemical Engineering from the University of San Agustin in Peru (1987) and worked for 5 years as an R&D engineer in a Peruvian company before coming to the U.S. for graduate studies. He received a Chemical Engineering M.S. degree from the University of Nebraska-Lincoln (1993) and the Ph.D. from the University of Wisconsin-Madison (1997). He joined the faculty of Cornell University at the end of 1998. He has been the recipient of several awards and recognitions including the Camille & Henry Dreyfus Foundation new faculty award, the Career Award from the National Science Foundation, the Alfred P. Sloan Foundation fellowship, the AIChE CoMSEF Impact Award, and the distinguished international UK visitor for CCP5. He also won an award for teaching excellence from the College of Engineering. He currently holds the Samuel and Diane Bodman Professorship Chair of Engineering.