Session: 04-23-01: Functional Soft Composites - Design, Mechanics, and Manufacturing

Paper Number: 141588

141588 - Dynamic Pressure-Sensitive Adhesion From Liquid Crystal Elastomers 

Nematic liquid crystal elastomers (LCEs) exhibit unusually high vibration damping, which has been assumed to cause their anomalously strong pressure-sensitive adhesion (PSA). Here we investigate the mechanism behind this enhanced PSA by preparing thin adhesive tapes with LCEs of varying chemical formulations, characterizing their material and surface properties, and examining their adhesion characteristics using a standard set of 90-degree peel, lap shear, and probe tack tests. Our findings confirm that the enhanced PSA is present only in the nematic phase of the elastomer, and that the strength of bonding takes more than 24 hours to reach its maximum value. This extended saturation time is due to the slow relaxation of local stress and director orientation in nematic domains after pressing against the surface. We demonstrate this mechanism by showing that a freshly pressed and annealed tape achieves the same maximum bonding strength upon cooling, when the returning nematic order is forming in its optimal con figuration in the pressed film

Presenting Author: Mohand Saed University of Cambridge

Presenting Author Biography: Dr. Saed is a University Royal Society Fellow at Cavendish Laboratory at Cambridge University. His research focuses on developing smart, sustainable, and stimuli-responsive polymers. His wide-ranging research interests include the designing new materials, additive manufacturing, vitrimers, stimuli-responsive polymers, plastic compounding, adhesives, and liquid crystalline elastomers (LCE).
During his ten-year academic career, he has made a significant scientific impact in all the universities he has worked for. For example, during his time as a PhD student at the University of Colorado at Denver, he made a crucial contribution in the field of LCEs, where he helped solve their synthesis problems. His PhD dissertation was a paradigm shift in the field, as he was able to apply the robust and reliable click chemistry that made it possible to produce these materials at scale. The research output was published in seven papers and one US patent.
During his first postdoctoral work at the University of Texas at Dallas, he acquired knowledge in various engineering disciplines in 3D printing and device microfabrication. Once again, he was incredibly successful there, where he played an essential role in developing a new technique to process LCEs via 4D printing, which is now widely used by many researchers worldwide. This research effort resulted in three additional papers and another US patent.
In recent years, Dr. Saed’s research interest focused on vitrimer materials. His goal was to apply the vitrimer concept to LCEs and also to commodity thermoplastic polyolefins. Since he came to Cambridge, he has published more than 25 original papers and applied for four patents, with several new papers in journals. In addition to academic work, he is a co-founder and Chief Technical Officer of Cambridge Smart Plastics Ltd, a spinoff company working to commercialise the vitrimer technologies he developed in Cambridge. Dr. Saed has raised more than $1.5 million in funding to support his research activities.
Dr. Saed has published more than 40 original papers, and 6 patents (3 granted, 3 filed), with 2000 citations and 24 H-index as of May 2023. He has consistently published in top-tier journals such as Chemical Reviews, Nature Communications, and Advanced Materials.

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