Directing Self-Assembly of Liquid Crystalline Block Co-Oligomers in Combined Optical and Magnetic Fields

University Of Pennsylvania, Philadelphia PA

Investigators

Abstract

NON-TECHNICAL SUMMARY Materials scientists seek to understand how the properties of materials are related to their structure and to develop methods to create the structures needed to achieve desired properties. Traditionally, scientists have focused on structure in terms of the arrangement of atoms and molecules that result naturally from the chemical composition of a material. However, in recent years new research has demonstrated that novel and often unanticipated properties can be realized by using human-made or synthetic material structures. This project aims to enable the creation of programmed spatial variation of optical and mechanical properties in polymeric materials as a new route to realize synthetic structures that can give rise to useful properties. This project aim will be advanced by fundamental studies that examine optically-driven structural transitions in designed light-responsive polymers and the magnetic field response of such polymers. Synthetic structures will be developed by the use of spatially-controlled dynamic light exposure in concert with magnetic fields. This project addresses a fundamental knowledge-gap regarding optically driven structural transitions in polymers, and processing methodologies to readily create spatial variation of properties in such systems. Controlling the spatial variation of properties provides a route for programming material function, and is sought in a variety of energy and microelectronics-related applications. It is therefore anticipated that this project will have broader impacts given the implications for the development of new materials in these sectors. This project involves a range of additional broader impacts including a new K-12 outreach program, the development of curriculum, a focus on recruiting diverse researchers, and the involvement of undergraduate researchers. TECHNICAL SUMMARY Controlling structural order in self-assembled polymers remains a critically important focus of research for materials scientists. Spatio-temporal control of optical fields, in concert with magnetic fields, could provide a highly versatile means of processing such materials. In this context, there is a critical need to understand and engineer photoswitchable ordering self-assembling polymers, and to develop new modalities for guiding self-assembly using optical fields. This project is centered on molecular design and characterization of photoswitchable liquid crystalline block co-oligomers (LC BCOs), and the development of strategies for controlling their structural order using optical fields, and optical fields in combination with magnetic fields. These systems provide a rich landscape in which to explore ordering transitions in the presence of optical fields, and in which to develop new modes of directed self-assembly using optical fields in concert with magnetic fields. The proposed work targets these opportunities and is geared overall towards developing new materials and understanding their structure-property relationships, and leveraging photo-responsive ordering to realize new, more versatile, modalities for directed self-assembly. The specific objectives are: 1. Elucidate phase behavior and photo-driven ordering in LC BCOs and their blends 2. Create spatially-varying textures programmed by spatially-varying optical fields 3. Develop combined optical and magnetic field processing The intellectual merit stems from the systematic exploration of self-assembly and phase behavior of a still emerging class of macromolecules, and the realization of a versatile modality for directed self-assembly that has been elusive to date. Successfully executed, the proposed work will provide critical insight regarding the manipulation of effective interactions in LC BCOs using optical fields and will enable the realization of complex spatially varying textures with unprecedented fidelity. 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.