Photoclickable Surfaces for Profluorescent Covalent Polymer Coatings

The nitrile imine‐mediated tetrazole‐ene cycloaddition reaction (NITEC) is introduced as a powerful and versatile conjugation tool to covalently ligate macromolecules onto variable (bio)surfaces. The NITEC approach is initiated by UV irradiation and proceeds rapidly at ambient temperature yielding a highly fluorescent linkage. Initially, the formation of block copolymers by the NITEC methodology is studied to evidence its efficacy as a macromolecular conjugation tool. The grafting of polymers onto inorganic (silicon) and bioorganic (cellulose) surfaces is subsequently carried out employing the optimized reaction conditions obtained from the macromolecular ligation experiments and evidenced by surface characterization techniques, including X‐ray photoelectron spectroscopy and FT‐IR microscopy. In addition, the patterned immobilization of variable polymer chains onto profluorescent cellulose is achieved through a simple masking process during the irradiation.     

2010: A Small Space Odyssey with Luminescent Molecules

The road to molecular logic and computation in Belfast, Northern Ireland started with chemical sensors in Colombo, Sri Lanka. This journey is mapped out with reference to design principles, such as those for luminescent PET (photoinduced electron transfer) sensing. Applications such as those for blood electrolyte diagnostics, “lab-on-a-molecule” systems, and molecular computational identification (MCID) are also met along the way.     

The effect of solvent on postcuring in free radical photopolymerization

During free radical photopolymerization, with an increasing degree of conversion, the viscosity increased and vitrification occurred. The unreacted double bonds had difficulty diffusing to the reactive site in the vitrifying polymer. However, the free radicals generated in the vitrifying matrix could survive for a long time. Thus, the postcuring process occurred. In this study, free radical photopolymerization kinetics of methacrylate with or without solvent was investigated by real‐time FTIR, which was combined with a heating device. Results showed that without solvent, postcuring occurred only by heating at a higher temperature than the glass transition temperature of the polymer. However, with solvent, the postcuring occurred even at room temperature, where only a small amount of solvent was enough to cause postcuring. The lifespan of the free radicals inside the polymer was over 10 h. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44223.     

A chemically amplified molecular glass resist with an ionic photoacid generator and a single protection group

A molecular glass resist with an ionic photoacid generator and a single protection group (MR‐1) has been developed. MR‐1 exhibited good thermal properties, such as a 5% weight loss temperature (T_d5%) of 167°C and a glass transition temperature (T_g) of 80°C. MR‐1 showed the good sensitivity of 80 μC/cm² and high contrast of 4.9 with e‐beam exposure (50 keV). A relatively high resolution of 50 nm and low Line‐Edge‐Roughness of 3.8 nm were obtained by e‐beam exposure (100 keV). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39769.     

Expanding the Genetic Code in Xenopus laevis Oocytes

Heterologous expression of ligand‐gated ion channels (LGICs) in Xenopus laevis oocytes combined with site‐directed mutagenesis has been demonstrated to be a powerful approach to study structure–function relationships. In particular, introducing unnatural amino acids (UAAs) has enabled modifications that are not found in natural proteins. However, the current strategy relies on the technically demanding in vitro synthesis of aminoacylated suppressor tRNA. We report here a general method that circumvents this limitation by utilizing orthogonal aminoacyl‐tRNA synthetase (aaRS)/suppressor tRNA_CUA pairs to genetically encode UAAs in Xenopus oocytes. We show that UAAs inserted in the N‐terminal domain of N‐methyl‐D ‐aspartate receptors (NMDARs) serve as photo‐crosslinkers that lock the receptor in a discrete conformational state in response to UV photo treatment. Our method should be generally applicable to studies of other LGICs in Xenopus oocytes.     

Model for reaction‐assisted polymer dissolution in LIGA

A new chemically oriented mathematical model for the development step of the LIGA process is presented (LIGA is an acronym for the German words Lithographie, Galvanoformung, and Abformung). The key assumption is that the developer can react with the polymeric resist material to increase the solubility of the latter, thereby partially overcoming the need to reduce the polymer size. The ease with which this reaction takes place is assumed to be determined by the number of side‐chain scissions that occur during the X‐ray exposure phase of the process. The dynamics of the dissolution process are simulated by the solution of the reaction diffusion equations for this three‐component, two‐phase system, the three species being the unreacted and reacted polymers and the solvent. The mass fluxes are described by multicomponent diffusion (Stefan–Maxwell) equations, and the chemical potentials are assumed to be given by the Flory–Huggins theory. Sample calculations are used to determine the dependence of the dissolution rate on key system parameters such as the reaction rate constant, polymer size, solid‐phase diffusivity, and Flory–Huggins interaction parameters. A simple photochemistry model is used to relate the reaction rate constant and the polymer size to the absorbed X‐ray dose. The resulting formula for the dissolution rate as a function of the dose and temperature is fit to an extensive experimental database to evaluate a set of unknown global parameters. The results suggest that reaction‐assisted dissolution is very important at low doses and low temperatures, the solubility of the unreacted polymer being too small for it to be dissolved at an appreciable rate. However, at high doses or at higher temperatures, the solubility is such that the reaction is no longer needed, and dissolution can take place via the conventional route. These results provide an explanation for the observed dependences of both the rate of dissolution and its activation energy on the absorbed dose. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 25–37, 2005