Soft Material Assembly Assisted with Polymer Pen Nanolithography

The intrinsic thermodynamics of polymeric and molecular materials can drive assembly into advantageous structures on the nanometer length scale. Specifically, block copolymers with two or more chemically distinct and covalently linked blocks that are enthalpically immiscible have the propensity to phase separate. These phase-separated regions can conform to many interesting structures that have been useful in areas including lithography, optics, and membrane design. Likewise, molecular aggregates are structures that readily assemble to a similar macromolecular length scale and can have unique interactions with visible light. In these assemblies, the long-range order is limited by uncontrolled nucleation and growth. Well-defined long-range order in these materials can strengthen photonic coherence and can make them intriguing candidates for visible-light integrated circuits. With state-of-the art competencies at the Center for Integrated Nanotechnologies at Los Alamos National Laboratory, the structural assembly of soft materials can be assisted with polymer pen nanolithography. The polymer pen lithography technique is a novel approach to precise, high throughput application of soft materials onto a surface. In the case of polymeric assembly, strategic placement of defects can be used to predetermine nucleation sites and limit grain growth, effectively assisting the assembly process. In the case of molecular aggregates, printing of aggregate assemblies on the length scale of visible light can reduce the quantum incoherence of randomly assembled and multilayer grains. Here, a substrate can be pre-treated with a quasicrystalline-patterned poly(dimethylsiloxane) (PDMS) photoresist that is then photopolymerized to yield a durable and chemically selective defect architecture intended to influence the self-assembly of a poly(dimethylsiloxane)-<i>block</i>-poly(lactic acid) block copolymer. The structural and characteristics of the resulting assemblies are quantified using X-ray scattering and microscopy techniques.