Supramolecular ionics: electric charge partition within polymers and other non-conducting solids

Electrostatic phenomena in insulators have been known for the past four centuries, but many related questions are still unanswered, for instance: which are the charge-bearing species in an electrified organic polymer, how are the charges spatially distributed and which is the contribution of the electrically charged domains to the overall polymer proper-ties? New scanning probe microscopies were recently introduced, and these are suitable for the mapping of electric potentials across a solid sample thus providing some answers for the previous questions. In this work, we report results obtained with two of these techniques: scanning electric potential (SEPM) and electric force microscopy (EFM). These results were associated to images acquired by using analytical electron microscopy (energy-loss spectroscopy imaging in the transmission electron microscope, ESI-TEM) for colloid polymer samples. Together, they show domains with excess electric charges (and potentials) extending up to hundreds of nanometers and formed by large clusters of cations or anions, reaching supramolecular dimensions. Domains with excess electric charge were also observed in thermoplastics as well as in silica, polyphosphate and titanium oxide particles. In the case of thermoplastics, the origin of the charges is tentatively assigned to their tribochemistry, oxidation followed by segregation or the Mawell-Wagner-Sillars and Costa Ribeiro effects.73449551

A Quick Guide for Computer-Assisted Instruction in Computational Biology and Bioinformatics

Introduction: Computational Biology and Bioinformatics (CBB) are indispensable components in the training of life scientists [1–3]. Current curricula in the life sciences should prepare graduates who master quantitative and computer skills for increased levels of performance [4–6]. Equally important is that the application of the curricula is driven by an appropriate instructional paradigm and effective learning experiences. Teaching and learning with computers bring specific issues that should be considered beforehand by any instructor. The following Quick Guide for Computer-Assisted Instruction (CAI) outlines ten principles for effective teaching. The principles are aligned with current developments on human cognition and learning [7] and have been drawn from our own experience using CAI in seminars, tutorials, and distance education, in courses on Molecular Life Sciences at the undergraduate level, taught to majors in biology or in other subjects (e.g., nutrition, teaching of physics and chemistry, teaching of biology, sports). The Guide refers to the preparation, presentation, and assessment of CAI. It should be an aid for those who teach CBB with CAI in class, and it is expected to stimulate student motivation and deeper learning in CBB, thus making class time more effective and improving satisfaction of both students and instructors

Materials from renewable resources: new properties and functions

Sustainable production requires increasing use of raw materials from renewable sources, processed under mild conditions with minimal effluent production. These requirements are satisfied by using materials derived from biomass, in synergy with food and energy production. The possibilities of biomass are continuously enlarged by new findings, as in the intrinsic nanocomposite properties of natural rubber and the amphiphile behavior of cellulose that translated into new functional materials, including high-performance, flexible and conductive non-metallic materials. Other findings are allowing a better understanding of electrostatic phenomena that play a positive role in electrostatic adhesion and cohesion of nanocomposites made from biomass products. Moreover, this should allow the development of safe electrostatic separation techniques, suitable for the fractionation of crude mixtures of biomass residues. A current study on rubber electrostatics is showing its capabilities as a transducer of mechanical energy while providing clues to understand the performance of the dielectric elastomers used in robotic self-sensing actuators914CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP465452/2014-088887.284776/2018-002014/50906-

Natural rubber-clay nanocomposites: mechanical and structural properties

International audienceThe mechanical properties of non-vulcanized natural rubber and dialyzed natural rubber-clay nanocomposites have been studied by uniaxial deformations to evaluate the reinforcement efficiency of the clay. We show that while non-rubber molecules contribute to auto-reinforcement, removal of these molecules improves significantly the performance of clay as reinforcement agent. These mechanical properties are discussed in relation to morphological aspects of the clay characterized by TEM and SANS. The nanocomposites prepared by "latex-mixing" with aqueous dispersions of clay are found to contain completely exfoliated clay lamellae in coexistence with tactoids. Improved mechanical properties of the nanocomposites can be modeled by the high aspect ratio of exfoliated clay platelets coupled with immobilized rubber matrix. Interestingly, presence of tactoids does not appear to compromise the excellent reinforcement properties of the exfoliated platelets. At high deformations, strain-induced alignment of the clay exhibits anisotropic scattering, with anisotropy increasing with clay concentration and stretching

Evaluation of thermal and photo-oxidative ABS degradation with recycling purposes

The aim of this work is the evaluation of thermal and photo-oxidative degradation of the terpolymer acrylonitrile-butadiene-styrene, ABS, used in internal automotive components. Injection molded specimens were aged by ASTM D794, ASTM G24 and ASTM G53 standards. The aged test specimens were studied by means of dynamic mechanical analysis and non-contact atomic force microscopy. The results revealed that the transitions of the glass and rubber phases were affected by the degradation. The area under linear loss modulus-temperature curves was related to tensile properties in function of the aging time and standard test method. The degradation of the matrix had a higher influence on the mechanical properties. Both, PB and SAN phases, were more affected when the ASTM G24 standard test method was used. Microscopy images showed that the different ageing methods cause different changes on the surface roughess. The results showed that an ABS that had lost 50 % of rupture elongation has this property almost regenerated (90 %) after being reprocessed.Este trabalho tem como objetivo avaliar a degradação térmica e fotooxidativa do terpolímero poli (acrilonitrila-butadieno-estireno), ABS, utilizado em componentes internos de automóveis. Corpos de prova de ABS moldados por injeção foram submetidos ao envelhecimento térmico, segundo a norma ASTM D794, e ao envelhecimento fotooxidativo segundo as normas ASTM G24 e G53. As amostras envelhecidas foram submetidas às análises dinâmico-mecânica, e microscópicas por microscopia de força atômica no modo não contato. Os resultados mostraram que as transições, tanto da fase vítrea quanto da fase elastomérica na superfície do ABS, são afetadas pela degradação. As áreas dos picos das curvas de módulo de perda em função da temperatura relativos às transições vítreas do ABS foram correlacionadas ao alongamento na ruptura, em função do tempo e tipo de envelhecimento. As propriedades mecânicas são influenciadas de forma mais acentuada pela extensão da degradação da matriz. O método de envelhecimento ASTM G24 mostrou-se mais agressivo que o G53, seja para a fase BR ou para a fase SAN. As imagens microscópicas mostraram que os diferentes envelhecimentos provocaram diferentes variações na rugosidade das superfícies. Amostras fotooxidadas, com perda de alongamento maior que 50%, foram reprocessadas e mostraram uma recuperação superior a 90% nessa propriedade.166172Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

AMPc - Intracellular signaling: an educational software

Chemicals binding to membrane receptors may induce events within the cell changing its behavior. Since these events are simultaneous and hard to be understood by students, we developed a computational model to dynamically and visually explore the cAMP signaling system to facilitate its understanding. The animation is shown in parts, from the hormone-receptor binding to the cellular response. There are some questions to be answered after using the model. The software was field-tested and an evaluation questionnaire (concerning usability, animations, models, and the software as an educational tool) was answered by the students, showing the software to be a valuable aid for content comprehension.48949

Chemistry post 2022 movement : formulation of an action plan so that chemistry and its actors impact the sustainability and sovereignty in Brazil

Considering the bicentenary of Brazil’s Independence in 2022 and that this year was proclaimed by UNESCO as the International Year of Basic Sciences for Sustainable Development, in mid-2021 the Brazilian Chemical Society (SBQ) launched the "Post 2022 Chemistry Movement – Sustainability and Sovereignty", with the main goal of promoting different activities so that chemistry contributes for the sustainable development and sovereignty of Brazil in the coming years. One of these activities is the proposal of an action plan, with goals to be achieved by 2030 and 2050. This article describes in detail how this action plan was formulated by a working group, with the help of an advisory council and interviews of 18 professionals from universities, the government, industries, the third sector and other organizations. Mimicking the Agenda 2030 SDGs, the resulting action plan is based on two broad Chemistry Sustainable Development Goals: promoting sustainability through chemistry in basic education, and promoting sustainability in the industry and university through science, technology, innovation, and education (STI&E) in chemistry. After the definition of three driving technological challenges in STI&E, they shall be successively implemented through different actions starting in 2023 yet