2023 Julian C. Smith Lectures

Charge-neutral polymer complexes as battery components

Monday, April 10, 2023 / 4:30 p.m. / 155 Olin Hall

Polymeric components may impart mechanical durability and decreased flammability to electrochemical devices like batteries, but must have higher performance in order to gain widespread use. Realizing high conductivity is a particular challenge as long- range ion transport is directly related to the dynamics of the matrix (viscosity) and is ultimately limited by the sluggish dynamics of polymers.

In this talk, I will discuss superionic conductivity in which the ion motion is decoupled from matrix dynamics and instead occurs through free volume elements in the structure. Semi-crystalline zwitterionic polymers appear both to demonstrate superionic conductivity and also very high salt solubilities due to their polarizability. As a result, they have both high Lithium ion conductivities (10-3 S/cm) and cation transport numbers (t+=0.67) despite their modest glass transition temperatures (0-25°C).I will also discuss new coacervate-based battery binders that demonstrate both high ion and electron conductivities and their use to in composite electrodes compatible with polymer electrolytes.

Using bioinspired polypeptoids to understand how chain shape influences self-assembly and water dynamics

Tuesday, April 11, 2023 / 4:30 p.m. / 155 Olin Hall

Polypeptoids are non-natural, sequence specific polymers that offer the opportunity to probe the effect of monomer sequence, charge, chirality, and chain shape on self-assembly and surface properties. Although examples of hierarchical polypeptide structures abound in nature, the de novo design of such systems is still a major challenge.The polypeptoid system with its much simplified set of inter and intramolecular interactions provides an opportunity to explore this design space with more tractable systems.

In this talk, the role of chirality and molecular helicity in relatively simple block copolymer architectures as well as the more complicated assembly of achiral molecules into homochiral superstructures will be discussed. While helical chain shapes in block copolymers have been shown to produce unique morphologies, polypeptoids provide a unique opportunity to understand the details of how chain shape influences the thermodynamics of self- assembly. I will also discuss the use of polypeptoids to modify water dynamics for applications ranging from highly specific water purification to highly efficient marine anti-fouling coatings.