Affiliation: College of Arts and Sciences, Department of Applied Physical Sciences, Materials Science Graduate Program
This research describes the development of unique methods to create patterns from 2D structure in molecular level to surface lithography and finally controlled reversible motions of macroscopic object. Mixing of chemically incompatible substances is a canonical problem that is particularly challenging for macromolecules. Here, we present an assembly strategy to create patterns of long range arrays of perfectly mixed, i.e., intercalated, macromolecules at a fluid interface via entropic release of steric repulsion between brush-like polymers. Such entropic templating (ET) strategy was successfully applied to mixtures macromolecules with a variety of polymer architectures and enables long range patterning of thin films on sub-100 nm length scales. Shape memory polymers have been particularly attractive for scientists as they allow for large, drastic, and highly complex shape transformations in response to a vast array of external stimuli. Here we describe a new non-invasive tool for local stimulation of shape transformations within a shape memory polymer using acoustic irradiation. This new technique can trigger shape transformations in optically non-transparent media at distances exceeding tens of centimeters and also allows discrete site-specific shape transformation in both time and space and potentially have applications in lithography. Irreversibility is the major drawback of the shape memory polymers. To incorporate reversibility into programmable shape memory, we introduce a universal protocol for three shape memory behavior, the conventional, one time reversible and multi time reversible shape memory. With the new protocol, we can create programmable spontaneous reversible motions and control the reversibility via material properties or experimental conditions. Further studying into the kinetic nature of crystallization process also leads to development of new protocols for triple shape memory with isothermal crystallization. Further research on the new protocols sheds more light on links between microscopic crystalline and macroscopic shape.