Iridescent polymers

A range of fibres marketed by Meadowbrook Inventions Inc. produce their iridescence in fibres by a tme light interference effect. This is achieved by constmcting the fibre from polymers having different refractive indices, similar to that which results from interference in thin multi-layers of polymer fllms. ... 

Owing to the simphcity and versatility of surface-initiated ATRP, the above-mentioned AuNP work may be extended to other particles for their two- or three-dimensionally ordered assemblies with a wide controllabiUty of lattice parameters. In fact, a dispersion of monodisperse SiPs coated with high-density PMMA brushes showed an iridescent color, in organic solvents (e.g., toluene), suggesting the formation of a colloidal crystal [108]. To clarify this phenomenon, the direct observation of the concentrated dispersion of a rhodamine-labeled SiP coated with a high-density polymer brush was carried out by confocal laser scanning microscopy. As shown in Fig. 23, the experiment revealed that the hybrid particles formed a wide range of three-dimensional array with a periodic structure. This will open up a new route to the fabrication of colloidal crystals. 

Thunig C, Hoffmann H, Platz G (1989) Iridescent colors in surfactant solutions. Progr Colloid Polym Sci 79 297-307... 

Coatings derived from cholesteric liquid crystalline polymers are used commercially as reflective sheets and polarisers. The liquid crystal is cooled below the vitrification temperature resulting in a solid polymer that is amorphous but contains large regions of frozen liquid crystalline order. Such structures are also found in nature in the iridescent, almost metallic colours of beetles and other insects, which result from helical cholesteric structures in the outer layer of the carapace. 

Thunig, C., Hoffmann, H. and Platz, G. (1998) Iridescent colors in surfactant solutions. Prog. Colloid Polym. Scl, 79, 297-307. 

Cholesteric oily streak textures could again be clearly observed for these LC polymers containing chiral spacers. In general, the pitch of the helical packing increased in a regular manner not only with temperature, as judged by an iridescent color, but also with the amount of achiral component in the copolymers. 

The first report in the open literature concerning cellulose derivatives is that of Werbowyj and Gray [100], They observed that 20-50% aqueous solutions of HPC were birefringent and highly iridescent due to the cholesteric nature of the liquid crystalline phase. The formation took place at a higher polymer volume fraction than predicted by the Flory theory, because of some chain flexibility and of side group interaction. 

Liquid Crystaiiine Soiutions. Cellulose esters, when dissolved in the appropriate solvents at the proper concentration, show liquid crystalline characteristics similar to those of other rigid chain polymers (9) because of an ordered arrangement of the polymer molecules in solution. Cellulose triacetate dissolved at 30-40 wt% in trifluoroacetic acid, dichloroacetic acid, and mixtures of trifluoroacetic acid and dichloromethane exhibits brilliant iridescence, high optical rotation, and viscosity-temperature profiles characteristic of typical aniostropic phase-containing liquid crystalline solutions (10). Similar observations have been made for cellulose acetate butyrate (11), cellulose diacetate (12), and other cellulose derivatives (13,14). Wet spinning of these liquid crystalline solutions yields fibers... 

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