Directed Self Assembly of Triblock Terpolymer Films

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NON-TECHNICAL SUMMARY: Block copolymers are a class of polymeric materials whose molecules can come together when cast from solution to form intricate, regular three-dimensional internal structures called microdomains. These microdomains can have dimensions of a few nanometers (billionths of a meter) and above, and their geometry and chemistry can be controlled through the design of the block copolymer. Most work has focused on block copolymers with two types of microdomains, but this project examines the behavior of block copolymers in which three different types of microdomain are simultaneously present, producing a wide range of complex geometries. It investigates the conditions under which different arrangements of microdomains are formed in thin films of these materials, and it demonstrates their technological usefulness, in particular for semiconductor device manufacturing, where the microdomain patterns can be used to define features smaller than those available from conventional manufacturing processes. This may allow future scaling of devices to higher densities, producing cheaper and faster memories or microprocessors. Other applications include catalysis or filtration where surfaces are required with particular chemistry or porosity. The work will involve graduate and undergraduate students in an interdisciplinary environment combining experiment and theory. Outreach will include the creation of online learning materials, summer projects for teachers and community college students, and public activities at the Cambridge Science Festival.TECHNICAL SUMMARY: Block copolymers microphase separate into periodic nanoscale structures, making them candidates for a range of applications including nanolithography and filtration. The great majority of work on thin film block copolymers has focused on diblock copolymers, but triblock terpolymers, which include three different blocks in a linear or star architecture, enable a much wider range of thin film morphologies including tiling patterns, square symmetry patterns, and structures with 90 degree bends. The proposed work will show how the morphologies of triblock terpolymer films can be controlled via interplay between the polymer composition and the processing conditions, and how specific morphologies can be templated using topographical substrate features, using coordinated experiments and theoretical investigations using self consistent field theory. The combination of triblock terpolymer volume fractions, molecular architecture, interaction parameters, film thickness, and solvent annealing with template geometry and substrate surface chemistry provides a rich parameter space within which an understanding of the kinetics and thermodynamics of microphase separation as well as the formation of technologically useful structures can be accomplished. The broader impacts of this work originate from the transformative potential of triblock terpolymers to produce nanoscale patterns relevant to nanolithography and nanomanufacturing, both in the microelectronics industry and in fields where a chemically heterogeneous surface with specific geometry is required. The work will involve graduate and undergraduate students in an interdisciplinary environment combining experiment and theory. Outreach will include the creation of online learning materials, summer projects for teachers and community college students, and public activities at the Cambridge Science Festival.