Accession Number : ADA314858

Title :   Thermally Switchable Periodicities and Diffraction from Novel Mesoscopically Ordered Materials.

Descriptive Note : Technical rept. 1 Mar 94-30 Nov 96,

Corporate Author : PITTSBURGH UNIV PA DEPT OF CHEMISTRY

Personal Author(s) : Weissman, J. M. ; Sunkara, H. B. ; Tse, A. S. ; Asher, S. A.

PDF Url : ADA314858

Report Date : SEP 1996

Pagination or Media Count : 16

Abstract : Two novel switchable, mesoscopically periodic materials were created by combining crystalline colloidal array (CCA) self-assembly with the temperature-induced volume phase transition of poly(N-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.

Descriptors :   *OPTICAL SWITCHING, PHASE TRANSFORMATIONS, CRYSTAL LATTICES, POLYSTYRENE, ARRAYS, SPHERES, DIFFRACTION, EMBEDDING, VISIBLE SPECTRA, POLYACRYLAMIDES, COLLOIDS, BRAGG ANGLE.

Subject Categories : Electrooptical and Optoelectronic Devices

Distribution Statement : APPROVED FOR PUBLIC RELEASE