Photoswitching Using Visible Light: A New Class of Organic Photochromic Molecules

A versatile new class of organic photochromic molecules that offers an unprecedented combination of physical properties including tunable photoswitching using visible light, excellent fatigue resistance, and large polarity changes is described. These unique features offer significant opportunities in diverse fields ranging from biosensors to targeted delivery systems while also allowing non-experts ready synthetic access to these materials

Structural Confirmation of Exo-Olefin-Coupled Polyisobutylene Via Model Compound Synthesis and Characterization

We report the synthesis and characterization of a model compound representing exo-olefin coupled polyisobutylene (PIB). Under certain conditions during the in situ quenching of quasiliving PIB with hindered bases to yield exo-olefin-terminated PIB, remaining PIB carbocations can undergo addition to exo-olefin PIB to yield coupled PIB with a molecular weight approximately double that of the primary chains. Characterization of the signals that arise in H-1-NMR from the presence of coupled product has not yet been properly performed; the accurate chemical shifts of these products, specifically the exo-olefin product, have been in debate recently. Therefore, we carried out the synthesis of a model compound which mimics the exo-olefin coupled product, and through variations in the synthetic method were able to produce a range of exo- and endo-olefin coupled product mixtures. The model compounds have been fully characterized using NMR techniques, and we herein conclusively report the proton shift (for 500MHz H-1-NMR in CDCl3) of 4.82 ppm for the exo-coupled product and that of 5.11 ppm for the endo-coupled product

Photoswitching using visible light: a new class of organic photochromic molecules.

A versatile new class of organic photochromic molecules that offers an unprecedented combination of physical properties including tunable photoswitching using visible light, excellent fatigue resistance, and large polarity changes is described. These unique features offer significant opportunities in diverse fields ranging from biosensors to targeted delivery systems while also allowing non-experts ready synthetic access to these materials

Cyclic Block Copolymers for Controlling Feature Sizes in Block Copolymer Lithography

Block copolymer lithography holds promise as a next-generation technique to achieve the sub-20 nm feature sizes demanded by semiconductor roadmaps. While molecular weight and block immiscibility have traditionally been used to control feature size, this study demonstrates that macromolecular architecture is also a powerful tool for tuning domain spacing. To demonstrate this concept, a new synthetic strategy for cyclic block polymers based on highly efficient “click” coupling of difunctional linear chains is developed, and the thin film self-assembly of cyclic polystyrene-<i>block</i>-polyethylene oxide (cPS-<i>b</i>-PEO) is compared with the corresponding linear analogues. The reduced hydrodynamic radii of the cyclic systems result in ∼30% decrease in domain spacing over the corresponding linear polymers

Clipping de 21/03/2018

Clipping de 21/03/2018: A crise civilizatória / Jéferson Dantas / Professor / Doutor em Educação / Oportunidade / Cheesecake Labs / Aplicativos / Startups / Expectativa / UFSC / Sistemas de Informação / Estudantes / Comissão de Transportes / Alesc / Palestra / Ônibus elétrico / Mutirão de avaliação das funções visuais em bebês será realizado no Arroio / Profissionais formados / Graduandos / Fisioterapia / Balneário Arroio do Silva / Programa de Pós-Graduação em Ciências da Reabilitação / Secretaria de Saúde / Fisioterapeuta e Mestranda / Giovana Pascoali Rodovanski / Terapias alternativas / Exercício físico supervisionado / Funções visuais / Bebês / Marcelo Câmara / Polifarmáci

Fabrication of unique chemical patterns and concentration gradients with visible light.

A modular and general method based on a photomediated ATRA reaction for the spatially controlled functionalization of surfaces with visible light is reported. The ability to control reactivity with light intensity combined with the orthogonality of ATRA chemistry allows well-defined chemically differentiated monolayers and complex nonlinear chemical concentration gradients to be easily prepared. Use of light to mediate these reactions permits spatial regulation and the generation of unique, multifunctional chemical gradients

Strongly phase-segregating block copolymers with sub-20 nm features

The modular synthesis and lithographic potential of diblock copolymers based on polystyrene-block-poly(2-ethyl-2-oxazoline) (PS-b-PEtOx) are highlighted herein. Controlled radical and living cationic polymerization techniques were utilized to synthesize hydrophobic PS and hydrophilic PEtOx building block of varying molar mass. Subsequently, "click" chemistry was used to couple the blocks and obtain a family of PS-b-PEtOx polymers. The influence of molar mass, composition, and thin-film thickness on the microphase-segregated morphology and orientation were investigated with atomic force microscopy (AFM) and grazing incidence small-angle X-ray scattering (GISAXS). Dense hexagonal arrays of cylindrical nanodomains normal to the substrate, having a periodicity of less than 2,0 run were obtained

Photoswitching Using Visible Light: A New Class of Organic Photochromic Molecules

A versatile new class of organic photochromic molecules that offers an unprecedented combination of physical properties including tunable photoswitching using visible light, excellent fatigue resistance, and large polarity changes is described. These unique features offer significant opportunities in diverse fields ranging from biosensors to targeted delivery systems while also allowing non-experts ready synthetic access to these materials

Fabrication of Unique Chemical Patterns and Concentration Gradients with Visible Light

A modular and general method based on a photomediated ATRA reaction for the spatially controlled functionalization of surfaces with visible light is reported. The ability to control reactivity with light intensity combined with the orthogonality of ATRA chemistry allows well-defined chemically differentiated monolayers and complex nonlinear chemical concentration gradients to be easily prepared. Use of light to mediate these reactions permits spatial regulation and the generation of unique, multifunctional chemical gradients