Ordering of Block Copolymer Systems with Enhanced Molecular Interactions and Diffusional Dynamics

University Of Houston, Houston TX

Investigators

Abstract

NON-TECHNICAL SUMMARY: Block copolymers are a class of multicomponent polymeric materials used for advanced applications in a wide range of nanotechnologies, ranging from membranes for cleaning oil spills to optical manipulation of light in fiber optics to fundamental elements of transistors and high-density data storage elements. Practical realization of such applications of block copolymer materials typically require that they form geometrically ordered structures, such as cylindrical or lamellar (sheet-like) microstructure and more complex geometries. While block copolymers can form these ordered structures intrinsically by self-assembly at molecular scales, obtaining ordered structures over macroscopic scales useful for applications requires providing the block copolymer with sufficient molecular mobility via processing methods. Thermal and solvent vapor processing methods are currently used, however, they can be slow and often not possible due to concerns of thermal degradation. The research here develops and examines in-depth a rapid processing approach that involves immersing the block copolymer into multi-component solvent mixtures that offer a controllable balance of swelling, non-swelling and block-interactions-tunable solvents. A successful research will pave the way for continuous roll-to-roll industrial processing for large-scale self-assembly of block copolymer structures for various applications. The research will promote participation of women and minorities through several educational and outreach activities, develop a polymer nanotechnology course with a laboratory module for Chemical Engineering and Materials Science graduate students, and engage high school students in laboratory research with internship programs. TECHNICAL SUMMARY: Block copolymers consist of chemically bonded monomer sequences whose ability to self-assemble renders them applicable for various potential nanotechnology applications, ranging from nanophotonics to nanoelectronics to nano-porous membranes. To accomplish these ordered self-assembly-driven microstructures requires advanced processing methods for controlled morphology and long-range order with minimal defects over macroscopic scales. While thermal and solvent vapor annealing (SVA) are established methods of block copolymer ordering, the work here will enable ordering of block copolymers annealed by a newly developed method involving its immersion in a mixture of solvents, while at the same time elucidating molecular-level understanding of the resulting morphology. Termed Direct Immersion Annealing, or DIA, the method has already demonstrated promise for rapid ordering of 2D cylinder-forming block copolymer films with unique control over domain spacing. The present work will examine DIA induced ordering of block copolymer films to study 1) chemical-potential controlled partitioning of solvent mixture within BCP blocks and activation energy of ordering, 2) role of intrinsic block copolymer morphology (1D, 2D, and 3D) on domain collapse in dry state, 3) ionic-liquid as a processing aid for enhanced ordering and targeted transport of functional nanoparticles selectively within BCP block domains, 4) fundamental kinetic and thermodynamic differences between DIA and SVA, and 5) effect of substrate surface energy on DIA-induced orientation and morphology of BCP films. Workforce aspects will involve the training of women and minorities through several educational and outreach activities, developing a bridging undergraduate-to-graduate polymer nanotechnology course, and provide scientific internships to high school students to learn about polymers, from a basic to an advanced level. . This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.