Lucas Pereira de Melo

Electrochemical comparison of two sulfonated styrene PEM membranes synthesized by different methods

The synthesis of two random copolymers was carried out by radical copolymerization. Poly(styrene-co-acrylic acid) in a 94:6 (St:AA) molar ratio, partially cross-linked with trimethylol propane trimethacrylate was synthesized by mass polymerization and then sulfonated (PSAAS-m) with sulfuric acid. On the other hand, the same random PSAA was synthesized by solution polymerization, but cross-linked with divinylbenzene and then sulfonated (PSAAS-s). Copolymers, including non sulfonated controls, were dissolved in THF and used to coat a platinum (Pt) electrode by “deep coating” and studied electrochemically by the voltamperometric cycle technique in 0.5xa0M H2SO4. Both non-sulfonated PSAA copolymers showed only a baseline signal, indicating no proton conductivity through them. The same result was obtained for the PSAAS-s copolymer, suggesting no proton conductivity as well. On the contrary, the copolymer synthesized in mass and highly sulfonated (PSAAS-m) showed the corresponding signals of Pt reduction, similar to the experiment carried out for the Pt electrode without any coating. Ion exchange capacity and water uptake measurements support the electrochemical findings.

A experiência de estudantes de enfermagem em um grupo de educação em saúde: uma abordagem dialógica - doi:10.5020/18061230.2011.p180

Objective: To conduct a theoretical reflection on the experience of nursing students in a group of health education, in Campinas-SP, having as theoretical and methodological nreferential the Dialogical Model. Data Synthesis: This was an experience report, conducted in a Health Center of Southwest Health District, located in Campinas-SP, in the period from nAugust to December 2009. This group was divided into 04 subgroups of on average 60 users each, being held diagnostic evaluation, identification of issues to be worked with users and planning and execution of group dynamics. The methodology developed in the educational activities was based on the theoretical Dialogical Model of Health Education. By means of group dynamics three changes were promoted in the way in which health education is thought and conducted: i) from a biologicist focus to the multidimensional apprehension of the individual; ii) through sharing, we learn: the principle of bidirectionality; iii) to know, not to know or do we know? The principle of symmetry. Conclusions: The viability and operability of the Dialogic Model for health education interventions is demonstrated.

Effect of the scaling-up the reactions synthesis of the poly(styrene-co-acrylic acid) polyelectrolyte at laboratory level

Sulfonated styrene-acrylic acid copolymers have been used as an alternative polyelectrolyte membrane for applications in fuel cells. In this work, the raw copolymer has been prepared by a well studied solution copolymerization reaction method, but at two different capacity reactor conditions: 100 mL and 3 L. The main idea was to scale up the copolymer production for having enough material for future sulfonation reactions. The reaction conditions consisted of styrene/acrylic acid in a 94/6 % mol, BPO as radical initiator in a 0.045 % mol, divinyl benzene (DVB) as crosslinking agent at 0.25 %mol and the solvent diethyl benzene (DEB) in a 50/50 volume ratio with monomers. Temperature was kept at 90 °C and the system stirred at 200 rpm during 2 hours, for both reactors. Molecular weight of copolymers was obtained by means of GPC, glass transition (Tg) by DSC and decomposition temperature (Td) through TGA analysis.