Method of manufacturing of a cholesteric layer

\u3cp\u3eThe invention pertains to a method of manufacturing a layer of a cholesterically ordered polymer material, in which the material is oriented in such a way that the axis of the molecular helix of the cholesterically ordered material extends transversely to the layer, wherein the method comprises the steps: a) providing a layer comprising a cholesterically ordered mixture of a low-molecular weight polymerizable material and a high-molecular weight material, which high-molecular weight material comprises a quantity of a convertible group, which in its non-converted and in its converted state determines the pitch of the material to a different extent, the conversion of said high-molecular weight material being inducible by radiation, and the layer absorbs said radiation; b) irradiating the layer to convert at least a part of the convertible groups in the irradiated parts of the layer; c) letting at least the low-molecular weight material reorient to form the required helical structure; d) at least partially polymerizing and/or cross-linking the low-molecular weight material with itself and/or with the high-molecular weight material to freeze in the formed structure.\u3c/p\u3

Spectral detector comprising a cholesteric liquid crystal mixture

\u3cp\u3eThe invention relates to a method for manufacturing a spectral detector including a photo detector array and cholesteric liquid crystal material for measuring properties of light over portions of the electromagnetic spectrum. By exposing the cholesteric liquid crystalmaterialfor different exposure intensities or exposure times of ultraviolet radiation at different positions on the cholesteric liquid crystal material in a controlled way, portions of the cholesteric liquid crystal material are obtained, each having, in general, its own optical transmission. This invention also relates to a spectral detector manufactured by the inventive method.\u3c/p\u3

A device for monitoring exposure to radiation, use of such a device, an article and a method for monitoring exposure to radiation

\u3cp\u3eA device (1) for monitoring exposure to radiation (L), particularly ultraviolet radiation, at least comprising cholesteric liquid crystal material (3) having a photo- isomerisable compound, such that during use, a light reflection band of the cholesteric liquid crystal material (3) can be modified upon exposure to the radiation to be monitored. The invention also provides a method for monitoring exposure to radiation.\u3c/p\u3

Static secondary ion mass spectrometry of poly(butylmethacrylates) : fragmentation reactions of four isomeric butanolate anions

\u3cp\u3eThe negative secondary ion mass spectra of the four isomeric poly(butylmethacrylates) are presented. The four isoineric butanolate anions which are formed fragment in a way which is specific for each isomer. In all cases, α,β‐elimination (relative to the oxygen atom) of suhstituents from the parent anions plays an important role. The mechanism of elimination of alkanes and molecular hydrogen from the butanolate anions is explained by the formation of hydride or alkyl anions from the α‐position of the butanolate anions. These newly generated ions abstract a proton or, with less probability, an aikyl subsrituent from the β‐position.\u3c/p\u3

Patterned layer of a polymer material having a cholesteric order

\u3cp\u3eThe invention relates to a method of manufacturing a patterned layer of a polymer material having a cholesteric order, in which the material is oriented in such a way that the axis of the molecular helix of the cholesterically ordered material extends transversely to the layer, and in which the layer is patterned in that it comprises at least one region in which the pitch of the molecular helix differs from that of another region. This inventive method comprises the following steps: a) providing a layer of a cholesterically ordered material comprising a quantity of a convertible compound which in its non-converted and in its converted state determines the pitch of the cholesterically ordered material to a different extent, in which the conversion of said compound may be induced by radiation, b) irradiating the layer in accordance with a desired pattern so that at least a part of the convertible compound in the irradiated parts of the layer is converted, c) polymerizing and/or crosslinking the cholesterically ordered material to form a three-dimensional polymer. The convertible compound preferably comprises an isomerizable, chiral compound. Polymerization and/or crosslinking are preferably induced by irradiation using electron-beam radiation or actinic radiation.\u3c/p\u3

Stable anisotropic films obtained by in-situ photopolymerization of discotic liquid crystalline acrylates

\u3cp\u3eNew discotic liquid crystals with one, two, or three reactive acrylate end groups were synthesized. They exhibit a wide discotic nematic phase and show spontaneous homeotropic alignment between substrates. The photoinitiated polymerization of these materials was studied. In-situ photopolymerization of these disklike acrylates leads to transparent and thermally stable films with a negative birefringence.\u3c/p\u3

Densely cross-linked liquid crystal networks by controlled photopolymerization of ordered liquid crystal monomers:properties and applications

Polymers with a controlledmolecular organization in all three dimensions are of interest because of their unusual, but very accurately adjustable and addressable optical, electrical, and mechanical properties. An established method to produce 3-D ordered polymers is the photoinitiated polymerization of liquid crystal (LC) monomers [1-4]. The variety in possible LC phases of low-molar-mass reactive mesogens provides diversity in the choice of the type of the molecular order, all being accessible to be fixed by the polymerization process [5-8]. Known techniques to establish monolithic molecular order in LCs, such as rubbed surfaces, surfactant-treated surfaces, external electric, or magnetic fields or flow, can be applied or even can be combined with each other to create films of even more complex molecular architectures [9]. The molecular structure of LC monomers can be tailored, for example, to optimize on the mechanical and optical properties of the films. Furthermore, blends of monomers can be made to adjust the properties in the monomeric state, such as the LC transition temperatures and the flow viscosity, and in the polymeric state, such as the elastic modulus, the glass transition (Tg) temperature, and the refractive indices

Surface modification of polymethylmethacrylate by UV light as studied by TOF‐SIMS

\u3cp\u3eIn the present paper the chemical modification upon exposure with UV light of 185 nm and 254 nm in an Ar atmosphere of the surface of polymethylmethacrylate (PMMA) is studied with time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS). The results show that UV photodegradation of PMMA does not induce large changes in the TOF‐SIMS spectra. However, changes in the relative peak intensities for the photolysed samples and comparison with results from PMMA fragmentation upon ion bombardment show that the photodegradation has proceeded to a considerable extent. In addition, small peaks are observed due to ions that originate from oxidized PMMA groups.\u3c/p\u3