Synthesis, properties and photopolymerization of liquid crystalline dioxetanes

Abstract

The synthesis and photopolymerization of various liquid crystalline dioxetanes is described. The effects of the spacer length, structure of the mesogenic group and oxetane group on the liquid crystalline properties, polymerization behaviour and optical properties (birefringence) of the oriented and crosslinked network formed in photo-polymerization are discussed. Thermally stable films with birefringence values up to 0.13 can be formed from these materials. The dioxetanes show significantly lower polymerization shrinkage than do structurally related diacrylates.

Solution‐Processed Full‐Color Polymer Organic Light‐Emitting Diode Displays Fabricated by Direct Photolithography

“…[28][29][30] All polymers were copolymers, containing the monomer 2, to which the oxetane functionality is attached. For the green-and red-light-emitting polymers, chromophores emitting in the respective wavelength region were also copolymerized into the polymer chain.…”

Synthesis, Properties, and Photopolymerization of Liquid-Crystalline Oxetanes: Application in Transflective Liquid-Crystal Displays

“…Procedures described in the literature were used to prepare 4-(4-(4-(3-methyloxetan-3-yl)methoxybutyloxy)benzoyloxy)-2-methylphenyl 4-(4-(3-methyloxetan-3-yl)methoxybutyloxy)benzoate (1) [19], 4-(4-((3-methyloxetan-3-yl)methoxy)butoxy)benzoic acid (3) [25], and 4-(tetrahydropyran-2-yloxy)-3-methylphenol (5) [16]. All the other chemicals used in the synthesis were obtained from Aldrich.…”

“…The methyl group in the middle ring facilitates liquid-crystalline behavior in the supercooled state, which should make room-temperature processing possible. [19] The phase transitions of 1 are also presented in Figure 2. The melting point of 1 is sufficiently low to avoid unwanted thermal polymerization if this compound is mixed with a cationic photoinitiator and melted into the liquid-crystalline phase.…”

“…[19] It was found that almost complete conversion was obtained at temperatures above 70°C, while polymerization at 30°C resulted in only less than 10 % conversion. In order to study the polymerization behavior of a mixture of 1 and 2 in a ratio of 75:25 (w/w), the conversion was determined as a function of the polymerization temperature by photo-differential scanning calorimetry (photo-DSC).…”

“…[17] A high thermal stability is a prerequisite for application in transflective LCDs as the LCD manufacturing process involves several high-temperature steps, such as the sputtering process of the transparent electrode and the baking of the polyimide alignment layer. As an alternative to radical chain-reaction polymerization, oxygen-insensitive cationic ring-opening polymerization of liquid-crystalline di-epoxides [18] or liquid-crystalline di-oxetanes [19,20] can be used for the fabrication of anisotropic thin films. Oxetanes are preferred to epoxides when applied as optical films because epoxides have a relatively slow rate of polymerization and side reactions may occur.…”