Robust polymer colloidal crystal photonic bandgap structures

Abstract

New polymeric matrices are presented that embed organic colloidal crystalline arrays (CCA's) into mechanically stable photonic bandgap structures. We achieved these new matrices either by dispersing polystyrene CCA's with high molecular weight hydrophilic polymer [poly(ethylene glycol); (PEG)] or through in situ polymerization of hydrophilic monomers (acrylamide and acrylate functional PEG variants) about the CCA. CCA-dispersed PEG matrices exhibited strong red opalescence with a narrow peak at 614 nm and were sufficiently rigid to withstand repeated mechanical deformation. Visible photonic bandgaps also were observed from free-standing CCA composites with cross-linked poly(N, N-dimethylacrylamide) matrices. The results demonstrate the technological potential for robust organic photonic crystals.

Responsive properties of crystalline colloidal arrays formed by core-shell microspheres with pH and temperature sensitivities

“…[4][5][6] Crystalline colloidal arrays (CCAs) may be formed through the self-assembly of these particles, and the stimuli-responsiveness combined to their visible light diffraction make these structures interesting and useful. CCAs may be used as photonic gap materials 7,8 and biosensors, 9,10 mainly in the form of polymerized crystalline colloidal arrays, where the self-assembled hard spheres are fixed inside a crosslinked hydrogel matrix, which is responsive toward the external stimulus. With this system, Asher and co-workers developed sensors for a large range of analytes from glucose to metal ions.…”

Photonic Bandgap Composites

“…Specifically, colloidal crystals composed of polymeric arrays have been stabilized through encapsulation in hydrogel networks and have been referred to as a polymerized crystalline colloidal arrays (PCCAs). [10,12,15] The PCCA films contain at least 30 vol.-% water, resulting in their fragility and propensity for significant changes in optical performance with water content. Mechanically robust composite films composed of silica particles in acrylate polymers have exhibited band stop tuning with mechanical stress, though the time for the films to return to the optical characteristics of their unloaded state after the cessation of stress was 2±4 h. [16± 18] In this work, we present a procedure in which the optical qualities of a hydrogel based PCCA are retained in a highly durable and water-free composite.…”

“…Although poly(acrylamide) and its derivatives have been established as standard PCCA matrixes, [10] we have focused on the use of poly(ethylene glycol) (PEG) hydrogels to give unique PEG-based PCCAs. [15,19] Hydrogels are prepared by the photoinitiated free radical polymerization of methacrylate-functionalized PEG in the presence of an ordered CCA. Networks based on PEG tend to exhibit a wider range of amphiphilicity and may offer greater compatibility with subsequent chemistry and therefore greater versatility in tuning composite properties.…”

Templating hydrogels

“…This innovative use of applied fields makes it possible to obtain CCA self-assembly under high ionic strength conditions, when crystallization would otherwise not be obtained due to insufficient repulsion between beads. Foulger and coworkers introduced the use of PEG-based hydrogel monomers as alternatives to acrylamide-based hydrogels in such CCA-based templating [ 25 ]. Such a PEG-monomer-templated hydrogel was used to demonstrate mechanicolorimetric responses of the PCCA (polymerized CCA) [ 26 ].…”