Non-equilibrium processing of block copolymer (BCP) thin films via thermal zone-annealing promises to overcome significant challenges of traditional thermodynamic approaches to create defect free and long-range ordered functional films for high-tech applications. Thermal zone annealing involves passing a moving thermal temperature gradient across the plane of the film to locally melt and solidify the film. Recently a low temperature "cold zone annealing" or CZA version was demonstrated with promising results. Since most block copolymers will degrade at significantly high temperatures above melt point, CZA is broadly applicable to many block copolymer systems. Results for CZA on glassy cylinder forming PS-PMMA block copolymer films indicate up to an order of magnitude in enhanced ordering kinetics and alignment. Based on these promising results, key molecular mechanisms underlying the CZA driven ordering phenomena for BCPs will be examined at a fundamental level. This research will investigate these fundamental aspects of CZA using different block copolymers systems to illuminate general governing principles of CZA induced ordering of block copolymer thin film systems. An important component of the research plan relies on an Activation Energy (Ea) analysis of ordering of block copolymer in CZA from grain size growth or correlation length development as a function of CZA parameters of velocity (V), maximum temperature (Tmax), and gradient magnitude (G) and the BCP molecular weight (Mw) and block-block interaction parameter. In addition, the origin and mechanism of orientational alignment will be elucidated using both patterned and non-patterned substrates.
NON-TECHNICAL SUMMARY:
Block copolymer materials have been the focus over the last decade as potential solutions to a wide range of emerging nanotechnology needs from functional photonic materials to terabit density data storage devices. The major limitation to the use of these materials, however, is the presence of defects. This proposal will seek to understand the fundamentals of a new annealing platform that significantly reduces the barrier to defect removal. These fundamentals could lead to new processing techniques allowing advances in many industrially relevant fields. The PI's students will get experience at the Advanced Photon Source at Argonne National Lab allowing for exposure and training at national research facilities. An active component of the research is aimed at involving students at adjacent high-schools through the Akron Early College High School program as well the Post Secondary Distance Learning Opportunities (PSEOP) and through a new program between St. Vincent St. Mary's High School in Akron and the College of Polymer Science and Engineering involving both students and teachers. In addition, the research will involve minority and women participation in their research program and both the University of Akron and University of Arkansas at Little Rock are both well known for their high ratio of minorities and women in research programs. In addition, this research project at UALR would incorporate secondary high school science teachers during the summer through a program known as STRIVE. The exposure of the teachers to this research including synthesis and nanocharacterization would improve their science skills as well as their understanding of the field making them better educators.
Dynamic Zone Annealing: A Versatile Roll-to-Roll Method for Fabricating Anisotropic Diblock Copolymer Films for Nanotechnology Applications Dynamic zone refinement is an industrially scalable roll-to-roll manufacturing process that can be used for continuous, rapid prototyping of anisotropic diblock copolymer films for nanotechnology applications. These include nanoporous membranes for -- water filtration, oil-water separation, carbon dioxide sequestration, gas/moisture barrier films for food packaging, high-density data storage and next generation nanoelectronics. Researchers have re-juvinated the dynamic thermal technique demonstrated for polymer crystallization at Bell Laboratories in the 80's, originally developed for metals refinement, also invented at Bell Laboratories in the 50's. They have introduced a soft-shear mode to controllably fabricate vertical and horizontally aligned nanoscale morphology in diblock copolymer thin films, that scalable for manufacturing, and potentially amenable to the above nanotechnology applications. For instance, diblock copolymers with two distinct glassy (stiff) or glassy-elastomeric polymer blocks, with controlled UV-etchable and solvent swellable blocks, suitable for membranes have been macroscopically aligned in large sheets, not possible previously with other methods. This is an NSF Collaborative Research effort jointly between University of Akron (UA), Ohio and University of Arkansas at Little Rock (UALR), Arkansas. Graduate students conduct the research funded by the NSF-DMR program. As broader outreach, exceptionally talented students from a local high-school, St. Vincent St. Mary’s (STVM), have been engaged to conduct research after school hours at UA on zone annealing of polymer films along with other fundamental knowledge on processing polymer films for nanotechnology applications. Many of these students have won awards at local and state levels as a consequence of the program, while going on to STEM pathways in college. Recently, this broader outreach was extended to a pilot high school summer program at UA for talented students at Western Reserve Academy in Hudson, Ohio. All students undergo a general and laboratory specific safety indoctrination administered by UA staff and faculty prior to the research work. The research is leveraged by NSF-DMR Supplement and NSF-REU program.
