The substituted tetraphenylporphyrins palladium 5,10,15,20-tetrakis(2′,3′,5′,6′-tetrafluorophenyl-4′-octadecyloxyphosphonic acid)porphyrin ( 16) and palladium 5,10,15-tris(2′,6′dichlorophenyl)-20-(2′,3′,5′,6′-tetrafluorophenyl-4′-octadecyloxyphosphonic acid)porphyrin ( 17) have been studied as Langmuir monolayers and as zirconium phosphonate Langmuir-Blodgett (LB) films. Using a three-step deposition technique, symmetric and alternating zirconium phosphonate bilayers and multilayers were prepared. In these films, the porphyrin constituent resides in the hydrophobic region of the monolayer and the phosphonate substituents bind zirconium ions in the hydrophilic part. Films of the pure porphyrins and of mixtures with octadecylphosphonic acid (OPA) were prepared. Langmuir monolayers were characterized with pressure vs area isotherms and reflectance UV-vis spectroscopy. LB films were studied with transmittance UV-vis and X-ray diffraction. Control over chromophore interaction was achieved by chemical modification of the amphiphiles and by selection of appropriate transfer conditions. For example, reduced aggregation was seen in LB films of the tetraphosphonic acid substituted porphyrin 16 transferred at mean molecular areas (MMA) larger than the area per molecule of the substituted porphyrin. In these films, the porphyrin macrocycles are nonaggregated and oriented parallel to the surface. In contrast, the monophosphonic acid substituted 17 aggregates under all of the deposition conditions studied. The stability of the porphyrin LB films was examined by exposing the films to refluxing chloroform. UV-vis absorbance after immersion in chloroform confirmed conclusions that in films of 17, many of the chromophores are not tethered to the inorganic network and are easily removed, whereas in films of 16, all molecules bind to the zirconium phosphonate extended network, making these films very resilient. CM980636D (48) Petruska, M.; Talham, D. Unpublished results.

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1. ABSTRACT Recent research by Doane, Yang and Chien' demonstrated the use of cholesteric liquid crystals in multiplexed, high resolution, reflective displays. These materials utilize the bistability of the cholesteric planar and focal conic states for displays with a colored image on a black background. Many commercial applications of these materials, such as electronic books and newspapers, portable faxes and personal data assistants, require, or at least prefer, black-onwhite images. We report on relatively high polymer content ( 20% by weight) dispersions of cholesteric liquid crystals that produce a white, reflecting planar state. The polymer network appears to form cholesteric domains with varying pitch lengths resulting in planar states that reflect in the red, green and blue portions of the spectrum.Utilizing a black absorbing layer behind a display using these materials offers white images on a black background, or vice-versa. INTRODUCTIONLiquid crystals dominate the flat-panel display market. Supertwisted nematic (STh) and active matrix liquid crystal displays are used in virtually all lap-top computers. Both STh and active matrix liquid crystal displays utilize polarizers and color filters to produce the full color images now common in lap-top computer displays. The polarizers and filters reduce the transmission through these displays to much less than 10%, necessitating the use of power hungry back lights to produce the bright displays consumers demand. The STN and active matrix displays are therefore not suitable for many new portable electronic devices which require lower power flat-panel displays.The telecommunications industry built a world-wide wireless communications infrastructure to support the rapid growth in the use of cellular phones and pagers. This infrastructure makes possible a new generation of portable multipurpose communication devices that combine the functions of the cellular phone, pager, portable computer and fax machine into a single unit. Publishers envision electronic distribution of newspapers, magazines, books and manuals using tablets incorporating high resolution flat-panel displays. Success of these new technologies demands lightweight devices (less than 2 pounds) precluding the backlights and heavy batteries found in the current lap-top computer displays. Manufacturers are therefore rushing to develop bright reflective displays.Recently Yang, Chien and Doane reported development of bistable, reflective cholesteric displays.' Some of the earliest liquid crystal displays were based on cholesteric materials2 Optical metastability and storage effects were observed in the early 1970's for cholesteric mixtures?" None of these early cholesteric display devices developed commercially because of materials limitation, long response times and the introduction of twisted nematic displays, developed at about the same time. The reflective cholesteric displays developed at the Liquid Crystal Institute utilize three different cholesteric configurations, Figure 1. The planar state reflec...