Direct Measurements of Mechanical Properties of Nanoconfined Ultrathin Polymer Films
Date: 2023/03/29 - 2023/03/29
Dissertation Title: Direct Measurements of Mechanical Properties of Nanoconfined Ultrathin Polymer Films
Speaker: Pei Bai, Ph.D. candidate at UM-SJTU Joint Institute
Time: 2:00 p.m., March 29th, 2023 ( Beijing Time)
Location: Room 414B, Longbin Building
Abstract
Mastering mechanical properties of polymers at nanometer scale is highly demanded yet remains challenging. Lack of abundant data for full characterization of nanoconfined polymers hinders better understanding of the mechanism that controls their unique mechanical behaviors. More efforts should be put into the study of the mechanical properties of the ultrathin polymer films. To achieve this goal, the most urgent task is to develop new test tools. This dissertation first developed a novel micro-vibrational system which enables direct measurements of viscoelastic properties of freestanding films. This apparatus was capable of the non-contact, dynamic test and confinement condition controls. Then, this system was applied to study the freestanding ultrathin polydimethylsiloxane (PDMS) films and striking changes of stiffness and the ratio between elastic and viscous responses with decreasing the film thickness were observed. These observations exhibit significant alterations of viscoelasticity under nanoconfinement. Moreover, this dissertation studied the soft and hard confinement effect on mechanical properties of ultrathin polystyrene (PS) films. These results reveals how the mechanical properties change when the polymer films are nanoconfined by the air-polymer interface or by the soft and hard neighboring domains. The findings from this dissertation reveals how the mechanical properties change when the polymer films are nanoconfined by the air-polymer interface or by the soft and hard neighboring domains. It provided new evidence toward gaining comprehensive understanding of nanoconfinement effect of soft matter. The results may shed a light for the better design and fabrication of the polymeric nanostructures, toward meeting mechanical property demands of emerging applications.
Biography
Pei Bai received his B.S. degree in School of Materials Science and Engineering from Beijing Institute of Technology in 2014. Now, he is a Ph.D. candidate student at the UM-SJTU Joint Institute, supervised by Prof. Yunlong Guo. His current research focuses on the mechanical properties of polymers under nanoconfinement.