Thermally Switchable Periodicities and Diffraction from Novel Mesoscopically Ordered Materials.
Technical rept. 1 Mar 94-30 Nov 96,
PITTSBURGH UNIV PA DEPT OF CHEMISTRY
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Two novel switchable, mesoscopically periodic materials were created by combining crystalline colloidal array CCA self-assembly with the temperature-induced volume phase transition of polyN-isopropylacrylamide PNIPAM. Body-centered cubic BCC CCA of hydrated, swollen PNIPAM particles Bragg diffract infrared IR, visible, and ultraviolet UV light weakly, while arrays of compact shrunken particles diffract efficiently. A tunable diffracting array was also created by embedding a CCA of polystyrene spheres within a PNIPAM hydrogel, that swells and contracts with temperature thus, the array lattice constant varies with temperature and the diffracted wavelength is thermally tunable across the entire visible spectrum. These materials may find applications in many areas of optics and materials science.
- Electrooptical and Optoelectronic Devices