A series of liquid crystalline homopolymers that have photoisomerizable cyanoazobenzene groups in the side chain has been synthesized and characterized. Thin films of these polymers have been processed in order to study the absorption spectra and circular dichroism responses after illumination with 488 nm circularly polarized light. The tendency of the azobenzene units to aggregate and the modification of the electronic spectra by illumination were studied by UV-vis spectroscopy. Illumination with circularly polarized light of the azopolymers gave rise to a photoinduced circular dichroism response, which suggests supramolecular structures with a chiral orientation of the azobenzene chromophores in H-aggregates. The photoinduced supramolecular order depends on the polymer structure, i.e., on the T g and the length of the flexible spacer, and the nature of the liquid crystal phase. Identical absorption spectra and reverse circular dichroism spectra were obtained after irradiation with circularly polarized light of opposite handedness and this is due to the photoinduction of enantiomeric supramolecular structures. The thermal stability above T g of the photoinduced supramolecular chirality is determined by the polymer structure.

Accurate quantum chemistry simulations remain challenging on classical computers for problems of industrially relevant sizes and there is reason for hope that quantum computing may help push the boundaries of what is technically feasible. While variational quantum eigensolver (VQE) algorithms may already turn noisy intermediate scale quantum (NISQ) devices into useful machines, one has to make all efforts to use the scarce quantum resources as efficiently as possible. We combine the so-called restricted approximation from computational quantum chemistry with techniques for simulating molecular chemistry on gate-based quantum computers and thereby obtain a much more resource efficient algorithm with little accuracy loss. In fact, we show that using the quantum resources freed up by means of the restricted approximation for increasing the basis set can lead to more accurate results and reductions in the necessary number of quantum computing runs (shots) by several orders of magnitude, already for a simple system such as lithium hydride.

Electrochemical chlorine production is one of the most energy-intensive processes in the chemical industry. Chlorine producers are interested in sustainable ways of optimizing these processes to reduce their energy consumption and carbon footprint. A significant improvement was made possible by Covestro and its technology partners by using the oxygen reduction reaction (ORR) and a gas diffusion electrode—the oxygen depolarized cathode (ODC)—in the electrolysis process. Energy savings of up to 30% can be achieved with this configuration. Gas diffusion electrodes are also used in fuel cells, and due to ongoing efforts in research and development, they are expected to enable the industrial implementation of new, sustainable electrochemical processes including electrosynthesis, water treatment, power generation, and energy storage.

IntroductionSince the 50s, numerous applications have been described for poly(vinylphosphonic acid) (PVPA) and its derivatives, [1][2][3] ranging from flame retardants [4,5] to cation exchange membranes, [6,7] dopants in conductive blends, [8,9] additives for coatings [10,11] or adhesion promoters in dental cements. [12] Additionally, PVPA exhibits a high solubility in water and high biocompatibility, [13] which renders a material for many other potential uses, like drug solubilization, cartilage / bone engineering or orthopaedic applications.In spite of this broad range of applications, information reported in the literature regarding synthesis and characterization of these materials is quite diffuse. Recently, however, microstructure characterization of PVPA and experimental observations characterizing the polymer as a polyelectrolyte have been reported by Bingöl et al. [14] There, it is suggested that the free radical polymerization of VPA carried out in the presence of 33 wt.-% water at 80 8C proceeds via cyclopolymerization of the vinylphosphonic acid anhydride as an intermediate.Here, we compare the polymerization of VPA in ethyl acetate and N,N-dimethylformamide (DMF) with the polymerization of VPA in acetic anhydride. Acetic anhydride Full PaperWe present the synthesis and characterization of the compounds formed in a mixture of vinylphosphonic acid (VPA) and acetic anhydride used for the radical-initiated VPA polymerization. High-molecular-weight PVPA with M w up to 109 000 g Á mol À1 was obtained from the polymerization of a mixture containing VPA, VPAAnh, VPADiAnh and their acetylated derivatives. Relative reactivities of these compounds were estimated. The resulting polymers were characterized by viscosimetry, light scattering and NMR measurements. The complexity of the polymer structure increases with increasing anhydride content in the reaction feed as can be concluded from the 1 H, 13 C and 31 P NMR spectra. This finding is in accordance with a cyclopolymerization mechanism resulting in five-and six-membered anhydride rings within the polymer chain. reacts with VPA forming different anhydride species. The reaction mixture is used for free radical polymerization and the polymerization behaviour of the different components is studied. Finally, the characterization of the resulting high molecular weight PVPAs by viscosimetry, light scattering and NMR is reported. Experimental PartMaterials VPA (BASF AG) was used as received with or without previous drying treatment (detailed below). 2,2 0 -Azoisobutyronitrile (AIBN, Aldrich) was recrystallized in methanol prior to use. Acetic anhydride (Fluka) was used without further treatment. DMF over molecular sieve (H 2 O 0.01%) was purchased from Fluka. Drying Treatment for VPAApproximately 25 g of VPA were introduced in a two-necked flask and a flow of N 2 was bubbled through at 60 8C under vacuum until volatile compounds were removed. By this procedure 5.5 wt.-% water with traces of methanol were removed from the crude monomer which was in agreement with its V...

Nitroxide-mediated radical polymerization (NMRP) was used for the synthesis of the random copolymer poly[styrene-r-(4-propargyloxystyrene)] with a narrow molecular weight distribution (PDI ∼ 1.2). The material was postfunctionalized by polymer analogous reactions and via Cu(I)-catalyzed 1,3-dipolar cycloadditions (“click chemistry approach”) to provide a family of photopatternable functional polymers for nanotechnology applications. For this, a series of azides were designed in order to incorporate subunits with specific properties into the materials. Photopatterning was made possible by the introduction of units with a photoremovable amino protecting group (PRG) (nitroveratryloxycarbonyl, NVOC) which may lead to the release of amino functions after selective UV/laser irradiation. Covalent attachment of the functional polymers onto gold was promoted by sulfide-containing anchoring units again introduced as pending groups onto the polymer backbone via the 1,3-dipolar cycloaddition reaction. The modified materials were obtained in almost quantitative yields under mild conditions according to IR and NMR studies. Thermal characterization was accomplished by DSC and TGA. Click chemistry is once more proven to be a useful tool for material science, in this particular case for the preparation of functional polymers for photopatterning with modulated properties.

We present the synthesis and characterization of a family of partially protected block copolymers and their precursors synthesized by means of nitroxide mediated radical polymerization (NMRP) and a sequence of quantitative and orthogonal polymer analogous reactions. The target materials consist of an unprotected 4-hydroxystyrene block and a tert-butoxycarbonyl (BOC) or a tert-butyl (TBU) protected block. Corresponding precursor block copolymers exhibit low polydispersity indexes (PDI) (<1.36) and show well-defined compositions of their blocks. Techniques like NMR, FT-IR, GPC, DSC, and TGA were applied in order to verify structure, compositions, molar masses, molecular weight distributions, and thermal properties. These materials are promising candidates for self-assembly in thin films and subsequent photolithographic patterning applications.

Biphotonic holographic recording has been performed on thin films of a side-chain liquid crystalline p-cyanoazobenzene polymethacrylate. Polarization and intensity holographic gratings have been recorded by irradiation of the films with blue incoherent light and simultaneous or subsequent illumination with the red light pattern generated by the interference of two properly polarized beams from a He–Ne laser. The influence of temperature and illumination conditions on the diffraction efficiency of those gratings has been studied. Surface topography of the films has been explored using a profilometer. The appearance of relief gratings using biphotonic processes has been observed only in gratings recorded with simultaneous illumination of blue light and an intensity modulated light pattern of the red light.

We present the synthesis and characterization of a series of photolabile phenacyl derivative polymers and their subsequent thin film preparation. These systems are composed of up to three methacrylate units: a photolabile component including a p-methoxyphenacyl moiety which after selective irradiation (UV/laser) can provide free carboxylic groups in specific areas for further modification; an anchoring unit, trimethoxysiloxane or glycidyl methacrylate derivative, which allows the covalent attachment of the polymer to the substrate; and a spacer, methyl methacrylate or styrene, which in the appropriate proportion ensures the formation of films with good quality. Structural and thermal properties of these materials have been analyzed by means of NMR, FTIR, elemental analysis, UV, gel permeation chromatography, differental scanning calorimetry, and thermogravimetric analysis. The polymers have been subsequently processed by spin coating to render ultrathin films (<50 nm). Topographic and structural characterization studies of the films have been carried out with atomic force microscopy, contact angle measurements, and X-ray photoelectron spectroscopy. The extent of the substrate attachment of the polymers depending on the nature of the anchoring groups have been studied by ellipsometry and FTIR.