Rollable ferroelectric liquid crystal devices monostabilized with molecularly aligned polymer walls and networks

This paper describes a flexible monostabilized ferroelectric liquid crystal (FLC) device using molecularly aligned polymer walls and networks, which are sequentially formed with a two-step photopolymerization-induced phase separation. When ultraviolet (UV) light was irradiated through a photomask onto a heated nematic phase solution of FLC and monomer, monomer molecules that had flowed into the irradiated areas were photopolymerized, and polymer walls aligned along the rubbing direction of the polyimide alignment layers on plastic film substrates were formed. After uniform UV irradiation without a photomask, polymer networks aligned along the rubbing direction were formed in the FLC. The FLC molecules were monostabilized in the rubbing direction by the strong anchoring of the polymer networks. The device, which was sandwiched between crossed polarizers, exhibited a monostable electro-optic characteristic with a high contrast ratio of over 100:1 and a response time of less than 1 ms. The FLC device exhibited spatially uniform operation even when it was rolled up with a radius of curvature of 1.5 cm.     

Synthesis and properties of conjugated polymers containing 3,9‐ and 2,9‐linked carbazole units in the main chain

Novel conjugated polymers containing 3,9‐ or 2,9‐linked carbazole units in the main chain were synthesized by the polycondensation of ethynyl‐ and iodo‐substituted 9‐arylenecarbazolylene monomers, and their optical and electrical properties were studied. Polymers with weight‐average molecular weights of 3400–12,000 were obtained in 76–99% yields by the Sonogashira coupling polycondensation in piperidine or tetrahydrofuran (THF)/piperidine at 30 °C for 48 h. All the 3,9‐linked polymers absorbed light around 300 nm. The para‐phenylene‐linked polymer also absorbed light around 350 nm, while meta‐phenylene‐linked one did not. The 3,9‐linked polymers absorbed light at a wavelength longer than the 2,9‐linked one. The polymers emitted blue fluorescence with high quantum yields (0.21–0.78) upon excitation at the absorption maxima. The polymers were oxidized around 0.6 V, and reduced around 0.5 V. Poly( 1 ) showed the dark conductivity of 3.7 × 10^?11 S/cm (10³ V/cm). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3506–3517, 2009     

Crosslinking of poly(-caprolactone) by radiation technique and its biodegradability

Poly(-caprolactone), PCL, (melting temperature, 60°C) was gamma-irradiated in the solid state at 30–55°C, the molten state, and the supercooled state (irradiation at 45–55°C after melting, 80°C) under vacuum to improve its heat resistance. Irradiation of PCL in the supercooled state led to the highest gel content and this polymer has high heat resistance. On the other hand, relatively smaller doses such as 15 and 30 kGy were effective to improve processability of PCL by formation of branch structure during irradiation.     

Radical ring‐opening polymerization

The radical ring‐opening polymerization (RROP) behavior of the following monomers is reviewed, and the possibility for application to functional materials is described: cyclic disulfide, bicyclobutane, vinylcyclopropane, vinylcyclobutane, vinyloxirane, vinylthiirane, 4‐methylene‐1,3‐dioxolane, cyclic ketene acetal, cyclic arylsulfide, cyclic α‐oxyacrylate, benzocyclobutene, o‐xylylene dimer, exo‐methylene‐substituted spiro orthocarbonate, exo‐methylene‐substituted spiro orthoester, and vinylcyclopropanone cyclic acetal. RROP is a promising candidate for producing a wide variety of environmentally friendly functional polymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 265–276, 2001     

Novel one-pot syntheses of sulfur-containing polymers from a bifunctional five-membered cyclic dithiocarbonate

Novel one-pot syntheses of sulfur-containing polymers from a bifunctional five-membered cyclic dithiocarbonate ( 1a ) were carried out. Polythiourethanes were obtained by the polyaddition of 4,4′-methylenebis(phenyl isocyanate), tolylene 2,6-diisocyanate, and hexamethylene diisocyanate with a dithiol ( 2a ) obtained by the reaction of 1a and benzylamine under mild conditions. Polythioesters were also obtained by the polycondensation of terephthaloyl and succinyl chlorides with 2a . Further, polythioether was obtained by the polycondensation of α,α′-dibromo-p-xylene with 2a . © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1189–1195, 1998     

Stereoselective Thermal Conversion of s-trans-Diallene into Dimethylenecyclobutene via s-cis-Diallene in the Crystalline State

A conrotatory [2+2] cyclization is the second step in the solid-state thermal reaction of s-trans-tetraaryldibromohexatetraenes 1 to cyclobutenes 4 . Prior to the cyclization 1 rearranges into the cis conformer 3 . Surprisingly the thermal rearrangement and the stereoselective cyclization occur readily in spite of the required motion of the sterically bulky substituents. R=Ph, p-MeC₆H₄.     

Radical ring-opening polyaddition of a bifunctional vinylcyclopropane bearing a spiroacetal moiety with dithiols

Radical polyadditions of vinylcyclopropane having spiroacetal moiety, 1,10-divinyl-4,8,12,15-tetraoxatrispiro[2.2.2.2.2.2] pentadecane ( 1 ), and various dithiols were examined. 1 was prepared by the reaction of 1,1-dichloro-2-vinylcyclopropane and pentaerythritol, and radical polyadditions of 1 and dithiols were carried out at 60 and 120°C for 20 h in the presence of an appropriate initiator (3 mol % vs. 1 ) in degassed sealed ampoules or at 20°C under photo irradiation by using a 400 W high-pressure mercury lamp. Poly( 1 ), pale yellow transparent viscous polymers was isolated by reprecipitation with ether containing a small amount of triethylamine to avoid hydrolysis of the polymer. The obtained polymers were soluble in chlorobenzene, DMF, and chloroform but insoluble in ether and n-hexane. The molecular weights of the polymers obtained from aliphatic dithiols were smaller than those from aromatic ones. The structure of the polymer was determined by comparing the NMR spectra with those of the model compounds, which were obtained by radical addition of 1 and benzyl mercaptan. The reaction proceeded through radical polyaddition of dithiol to 1 via radical ring-opening polymerization of the cyclopropane ring. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2487–2492, 1997     

Correlation Length Measurement of Sidewall Roughness of Dry Etched Facet and Its Effect on Reflectivity

Dry etching is an important tool to fabricate various semiconductor photonic devices. The roughness of etched sidewalls should be avoided as it reduces the scattering loss. We present a spatial frequency analysis of the sidewall roughness of dry etched facets processed by reactive ion etching. A characteristic parameter corresponding to a correlation length is estimated to be ∼0.5 μm. In addition, its effect on reflectivities of etched reflectors is discussed.