Date 2015-06-12 

Topic : Two-dimensional block copolymer materials: Transport and mechanical behavior

Speaker : Prof. Mark P. Stoykovich (Department of Chemical and Biological Engineering, University of Colorado)


Date :  June 12 (Fri),  14:00
Venue : KAIST Applied Engineering B/D(W1), Multimedia Lecture Hall (1st Floor)


■ Abstract : Here we will detail the nanostructured systems generated by block copolymers, both in terms of their fundamental material properties and their potential implementation in the nanofabrication of functional devices.  The transport behavior of small molecules, ions, protons, or electrons through nanostructured materials is often an important consideration for final device performance, for example in organic photovoltaics, solid electrolytes for batteries and energy storage devices, or nanofiltration membranes. Despite important and recent advancements in this field, specific transport pathways can be difficult to elucidate in the three-dimensional systems that have been considered, and relatively little is understood about the role of grain boundaries and the defects that populate these boundaries on the macroscopic transport behavior.  In general, the average transport properties of the material are characterized in combination with techniques such as scattering that provide information on average structure.  We have instead studied the topology of the two-dimensional patterns formed by lamellar block copolymers in thin films (sub-100 nm thickness).  Such a system is attractive for characterizing transport in block copolymers, as it allows for top-down characterization of the nanoscale morphology using electron or scanning probe microscopy techniques and provides a direct means for probing transport pathways in the network.  We have discovered that the topology (i.e., connectivity and continuity) of the lamellar network is a function of the types of defects and defect density formed during self-assembly, and thus, is a function of the composition of the copolymer system and the processing conditions.  We have also shown that the transport behavior of the lamellar morphology formed by block copolymers in thin films depends on the length scale over which it is characterized and can be described by percolation in a network under confinement.  In addition, the mechanical response of the nanostructured two-dimensional lamellar networks has been characterized in response to applied deformations and as a function of the network morphology