(604d) Well-Defined Polymer Adhesives Synthesis: Pendant Functionalities and Crosslinking Effect on Properties

Adhesives are nonmetallic polymer materials which possess the ability to join together two independent surfaces by chemical and physical bonding. Despite the importance of adhesives on various applications under complex environment, most of the existing adhesives are single purpose, single material-based, and singular in function. The talk discusses multi-functional adhesives that exceed conventional role of adhesive: 1) single-phase photo-crosslinkable adhesives which enhances adhesion strength by UV irradiation, 2) photo-degradable adhesive that reduce adhesion strength by UV irradiation, 3) Zwitterionic polymer-based adhesives that can be used in biomedical applications, 4) glucose-based adhesives which can form strong adhesion via copper free click reaction, 5) post-polymerization modification (oxime ligation functionalization) enabled bottle-brush type adhesives, 6) silicone nano cage-reinforced pressure sensitive adhesives and 7) Metal-free electrically conductive bioinspired adhesive polymers. Those listed special functionalities of new adhesives were possible due to chemical functional groups on the synthesized linear polymers. For instance, the photodegradable adhesives contains nitrobenzyloxycarbonyl crosslinker which can be cleaved under light exposure. The photocleavage of nitrobenzyl crosslinker yielded significant reduction of adhesion strength. Likewise, introduction of specialized functional group provides customized and extraordinary properties to the adhesive. In addition to the special functional group, crosslinking controls adhesion property by influencing polymer chain mobility, viscous flow, and creep behavior. The well-controlled crosslinking enhances adhesion property; however, too high crosslinking makes the polymer stiff. Too low crosslinking does not contribute to adhesion due to low viscosity of liquid-like polymers. The type of chemistry in crosslinking also have a strong effect on adhesive applications. For example, crosslinking method for biomedical adhesives should not involve in any toxic catalysts and/or byproducts. The talk will demonstrate strain-promoted azide–alkyne cycloaddition (SPAAC) as a new non-toxic crosslinking method for a biomedical adhesive. Overall, a series of new adhesives synthesis demonstrates how molecular building blocks, functional groups, architectures, and crosslinking of polymer can strongly affect polymer properties which govern adhesion.