EAPSI: Understanding Phase Separation in Multiblock Copolymers

Sarapas Joel M, Amherst MA

Investigators

Abstract

Commodity plastics, from grocery bags to touch screens, are ubiquitous in the American lifestyle and critical to our economy. Among these, materials made from block copolymers have become increasingly widespread, including extensive use in 3D printing, numerous shock resistant applications, and as fillers in asphalt. Current commercial block copolymers are typically molecular chains with two or three chemically distinct segments, or "blocks." While incorporating multiple chemistries into the block copolymer yields very interesting and often desirable properties, expanding the number of blocks past three can often enhance those properties, making even more valuable materials known as multiblock copolymers (MBCs). Understanding the properties and molecular behavior of MBCs is currently limited by their difficult synthesis. A series of MBCs containing polystyrene (PS) and polyethylene oxide (PEO) using thiol-ene radical coupling that was recently synthesized will be characterized to advance our understanding of MBC behavior. This research will be conducted in collaboration with Dr. Mikehito Takenaka, a world-class morphologist, at Kyoto University in Japan to help guide MBC use in possible commercial applications. The MBCs to be used in this study are comprised of PS and PEO chained together using thiol-ene radical coupling. PS and PEO block copolymers undergo phase separation if their molecular weights are sufficiently high due to their poor chemical mismatch parameter. Three MBCs will be studied: one that is expected to phase separate strongly, one weakly, and one not at all. The resulting morphologies will be analyzed by grazing incident small angle x-ray scattering and standard small angle x-ray scattering. Transmission electron microscopy and electron tomography will yield both 2D and 3D images of the materials. This data is expected to both broaden MBC knowledge and potential applications. This NSF EAPSI award is funded in collaboration with the Japan Society for the Promotion of Science.