Polymers provide a versatile materials platform for 1, 2 and 3D periodic nano-micro- scale composites with either dielectric or impedance contrast or both, and these can serve as photonic and or phononic crystals for electromagnetic and elastic waves as well as mechanical frames/trusses. Compared to electromagnetic waves, elastic waves are both less complex (longitudinal modes in fluids) and more complex (longitudinal, transverse in-plane and transverse out-of-plane modes in solids). Engineering of the dispersion relation between wave frequency w and wave vector, k enables the opening of band gaps in the density of modes and detailed shaping of w(k). Hierarchical periodic polymeric structures can be made by the bottom-up self assembly of block polymers and by top-down interference lithography and electron beam lithography. Band gaps can be opened by Bragg scattering, anti-crossing of bands and discrete shape resonances. Current interest is in our group focuses using design - modeling, fabrication and measurement of polymer based periodic materials for applications as tunable optics, control of phonon flow and ballistic/blast mitigation.
Reference:
Periodic Materials and Interference Lithography: For Photonics, Phononics and Mechanics, M. Maldovan and E.L. Thomas, (Wiley-VCH), 2009.