Combining Photodeprotection and Ligation into a Dual-Color Gated Reaction System

We report a photochemical reaction system which requires activation by two colors of light. Specifically, a dual wavelength gated system is established by fusing the visible light mediated deprotection of a dithioacetal with the UV light activated Diels–Alder reaction of an o-methylbenzaldehyde with N-ethylmaleimide. Critically, both light sources are required to achieve the Diels–Alder adduct, irradiation with visible or UV light alone does not lead to the target product. The introduced dual gated photochemical system is particularly interesting for application in light driven 3D printing, where two color wavelength activated photoresists may become reality.</p

Glasscheibe sowie Verfahren zur Herstellung der Glasscheibe

A method is described for producing a glass pane having at least one edge section which delimits the glass pane and for the production of which the glass pane has been severed along the edge section with the aid of a severing operation which comprises an introduction of thermal energy. The invention is characterized in that, immediately after production of the at least one edge section by means of a severing operation which comprises an introduction of thermal energy, the glass pane is surrounded by a covering at least in sections, preferably along the entire edge section

Light Induced Ligation of o-Quinodimethanes with Gated Fluorescence Self-Reporting

We introduce a highly efficient photoligation system, affording a pro-fluorescent Diels-Alder product that, on demand, converts into an intensively fluorescent naphthalene via E1 elimination in the presence of catalytic amounts of acid. The Diels-Alder reaction of the photocaged diene (o-quinodimethane ether or thioether) with electron-deficient alkynes is induced by UV or visible light. In contrast to previously reported ligation techniques directly leading to fluorescent products, the fluorescence is turned on after the photoligation. Thus, the light absorption of the fluorophore does not undermine the photoligation via competitive absorption, and as a result, photobleaching or side reactions of the fluorophore are not observed. Critically, the gated generation of a fluorescent product allows for fluorometric determination of the conversion. We employ a simple synthesis strategy for heterobifunctional electron-deficient alkynes allowing for facile functionalization of payload molecules.</p

Polymer networks based on photo-caged diene dimerization

A powerful, simple and efficient method for photochemical crosslinking, exploiting the self-dimerization of photo-caged dienes based on o-methylbenzaldehydes (o-MBAs) is introduced. Using a small molecule model system it is possible to identify the intermediate and final products of this light induced dimerization process. The bi-functional photocurable monomers contain o-MBA as well as vinylic units, which enables radical copolymerization with other monomers to tune the mechanical properties of the resulting networks. Crosslinked materials with reduced E-moduli ranging from 0.29 to 5.76 GPa and a hardness between 52 and 329 MPa were obtained, thus spanning a wide regime of different ‘soft’ to ‘hard’ material properties. The functional groups can be addressed through simultaneous reaction or in a λ-orthogonal fashion. This orthogonality can be achieved by inducing the free radical polymerization independently of the dimerization either thermally or via photoinitiation at a wavelength higher than the wavelength used for the non-radical dimerization process (>400 nm). Critically, this allows for a spatially defined adjustment of both the E-modulus and hardness within the respective material by controlling the irradiation parameters, such as wavelength, curing time and intensity. The introduced self-dimerizing resists thus represent a highly controllable combined radical/non-radical and λ-orthogonal curing system

Hybrid Photo-induced Copolymerization of Ring-Strained and Vinyl Monomers Utilizing Metal-Free Ring-Opening Metathesis Polymerization Conditions

We introduce the hybrid copolymerization of two disparate monomer classes (vinyl monomers and ring-strained cyclic olefins) via living photopolymerization. The living character of the polymerization technique (metal-free photo-ROMP) is demonstrated by consecutive chain-extensions. Further, we propose a mechanism for the copolymerization and analyze the copolymer structure in detail by high-resolution mass spectrometry.</p