Thermally Switchable Periodicities and Diffraction from Mesoscopically Ordered Materials

Abstract

Two 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 CCAs of hydrated, swollen PNIPAM particles Bragg-diffract infrared, visible, and ultraviolet light weakly, whereas 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 was thermally tunable across the entire visible spectrum. These materials may find applications in many areas of optics and materials science.

Preparation and Characterization of Novel Temperature and pH Sensitive (NIPAM-co-MAA) Polymer Microgels and Their Volume Phase Change with Various Salts

“…Effect of Temperature P(NIPAMco-MAA) Microgel Series: DLS measurements were used to judge the hydrodynamic radius in the temperature range of 20-70 o C of the polymer microgels at pH (3)(4)(5)(6)(7)(8)(9)(10)(11)(12). Hydrodynamic radius of the polymer microgel particles is dependent upon temperature.…”

“…A zeta plus zetameter (Brookhaven Instrument Corp., NJ) was used for the measurements of zeta potential. Polymer microgels surface charge density was determined from the electrophoretic mobility measurements at a temperature (20-55 o C) and pH (3)(4)(5)(6)(7)(8)(9)(10). The measurements were carried out as a function of pH (3)(4)(5)(6)(7)(8)(9)(10) at 25 o C. The measurements were performed in a background electrolyte concentration of 1×10 -3 mol dm -3 NaCl (In order to remove variability and to keep constant the length of electrical double layer, background electrolyte is used) solution.…”

Crystallization of Brownian Particles from Walls Induced by a Uniform External Force

“…5,6) On the other hand, since closed-packed-colloidal crystals are able to be used as templates for inverse opals with perfect three-dimensional photonic bandgaps, 7) the close-packed colloidal crystals have received more attention than the non-closed-packed colloidal crystal.…”

Tunable structural color in organisms and photonic materials for design of bioinspired materials

“…However, this type of colloidal crystal is unstable and can be destroyed even by a weak disturbance. Weissman et al have proposed a new soft material shown in figure 5(C), which is a colloidal crystal embedded in a poly(N-isopropylacrylamide) hydrogel [77]. The lattice spacing in this colloidal crystal is tuned by the temperature-induced phase transition in the hydrogel.…”