Research Projects

Engineering Material Performance through Network Architectures

Polymer networks form an integral part of our daily lives, with applications ranging from simple paper glue to complex polymer electrolytes, as a result of their versatility in the polymer chemistry backbone and their ability to sustain large reversible deformations enduring longer lifetimes. Despite these networks being so utilized in today’s society, predicting their mechanical properties remains a challenge, and material design as of today is still heavily based on a trial and error basis. This synthesis ordeal stems from the occurrence of topological defects such as loops, entanglements and dangling side chains in real networks, heterogeneities which are not accounted for in the well-established theories of linear elasticity. While during the last decade, there has been a concerted effort to relate observed mechanical behavior to the architecture of real networks, there still exists a missing link between the propagation kinetics, dependent on reaction conditions, to the resulting network architecture and eventual mechanical properties. Our work focuses on bridging this current gap in material synthesis, by controlling the network architecture and mechanical properties through tuning of the propagation kinetics, understanding the contribution of defects to material properties, and probing defects in real networks to build novel architectures with enhanced material performance.

Mechanics of Pressure Sensitive Adhesives

Tapes, labels and Band-Aids all use the same principle of pressure sensitive adhesion. A thin film of soft viscoelastic polymer is placed on the backing layer – that which is exposed after being adhered. This soft viscoelastic polymer is meticulously engineered to have liquid and solid like properties. Spontaneous (pressure sensitive) adhesion is achieved by the liquid properties that mirror those providing the sticky behavior of maple syrup. This subtle property is why tape doesn’t need to cure after being attached – compare this to any other adhesive. Solid like properties are required if the adhesive is to bear even small loads for any appreciable period of time. The mechanics of these class of materials pose interesting problems in fracture mechanics, fluid mechanics, and polymer physics. Ultimately, we aim to use this class of materials to gain a better understanding of material behavior in the regime between solids and liquids.

Multiscale analysis of failure
Macro view of debonding

Purification Membrane Lifetime and Performance

Freshwater scarcity is an increasingly prevalent issue around the world due, in part, to the increased frequency and severity of droughts and floods caused by climate change. Water purification technologies, therefore, are an important area of research. Polymer membranes are an important and well-established technology for water separation processes, such as desalination. Reverse osmosis (RO) membranes, in particular, are the most selective class of polymer membranes and thus are typically used for desalination. Highly pressurized water containing dissolved compounds is forced through the membrane which has pores that are only slightly larger than water molecules. Thus, salt is rejected from the water at extremely high rates. Challenges arise when the buildup of rejected salt impedes the flow of water through the membrane. This phenomenon, known as fouling, causes an increase in mechanical stress and is often addressed by the use of cleaning agents. However, cleaning agents often degrade membranes over time.  Thus, the high pressures of operation, fouling, and cleaning of membranes underpin the importance of the mechanical performance along with separation performance of the membranes. Despite this, however, mechanical and fracture properties of these membranes are vastly understudied in the literature. The current aim of this project is to develop a more complete mechanical test for reverse osmosis membranes. The goal is to be able to better understand the relationship of mechanical and fracture properties as they relate to membrane performance. Ultimately, it is hoped that this research will lead to the development of materials and membranes that resist degradation and preserve membrane performance. 

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