In this work, we report the effect of combining styrene-vinyl tetrazole copolymer (StVTz) and ammonium polyphosphate (APP) on the thermal degradation, mechanical properties, flame retardancy, and char formation of low-density polyethylene with ethyl vinyl acetate (LDPE/EVA) composites. The tetrazole heterocycle exhibits high thermal stability (>200 °C), and during its thermal decomposition, it releases non-toxic nitrogen gas. Its degradation generates reactive species capable of cross-linking the polymer chains, thereby promoting the formation of a protective char layer. To evaluate the influence of composition on the intumescent flame-retardant (IFR) properties of LDPE/EVA blends, different concentrations of APP and StVTz additives were incorporated. The composites were prepared in an internal mixer (Brabender Intelli-Torque Plasti-Corder). Test specimens were obtained by compression molding and subsequently cut into appropriate shapes for each analysis. Thermal stability was studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Mechanical properties were evaluated by tensile testing. Morphology of cone calorimetry (CC) residues was examined using SEM. Flammability properties, studied using CC, revealed a 70% reduction in the peak heat release rate (pHRR) and a 48% reduction in the total heat release (THR) compared to the neat LDPE/EVA blend. These results indicate that StVTz and APP act synergistically to improve the flame-retardant properties of LDPE/EVA.

Dye-sensitized solar cell (DSSC, DSC, DYSC, or Grätzel cell) are a semiconductor photovoltaic device that directly converts solar radiation into electric current. In contrast to conventional systems in which the semiconductor takes on both the task of absorbing light and transporting charge carriers, the two functions are separated in the DSSCs. The light is absorbed by a sensitizer, which is anchored to the surface of a broadband semiconductor. A typical DSSC consists of a mesoporous photoanode with a dye-sensitized titanium dioxide (TiO2) film, an electrolyte containing iodide/triiodide (I-1/I3-1) redox couple, and a counter electrode with platinum (Pt) catalyst. Upon the absorption of light energy, a photo-excited electron is injected from the excited state of the dye into the conduction band of the TiO2. However, the immobilization of the adsorbing dye molecules onto the surface of semiconducting metal oxide nanoparticles is crucial for initiating an electrical current, via the injection of electrons, which collectively act as the working electrode of a DSSC. Herein we report the synthesis, characterization, and evaluation of the compound 5-(4-octyloxyphenyl)tetrazole (LTz-5) as dye co-adsorbente to DSSCs. This dye was incorporated in DSSCs as a co-sensitizer with different other dyes (HD-2, HD-14, and MH-13), to evaluate the effect of interaction between dye and co-adsorbent on the energy conversion efficiency (%η). The energy conversion efficiency of the DSSC was 8.78 % from HD-2 – LTz-5 (4.9 % increase compared to CDCA), 9.20 % from HD-14 – LTz-5 (0.66 % increase compared to CDCA), and 5.01 % from MH-13 – LTz-5 (1.0 % reduction compared to CDCA). The latter results suggest that steric effects restrict the anchoring ability of the tetrazole groups, by hindering their approach to TiO2 surface and by restricting the coplanarity of the system.

A novel copolymer based on sulfonated N-alkylated styrene-vinyltetrazole was synthesized. Copolymers were prepared by a 1,3-dipolar Huisgen cycloaddition reaction from their corresponding previously synthesized styrene-co-acrylonitrile copolymers and subsequently alkylated with aliphatic chains of 4, 6 and 8 carbon atoms. Finally, they were sulfonated using H2SO4 as sulfonating agent for 4 hours. The chemical structure of the copolymers was analyzed by FT-IR and 1H and 13C NMR, the thermal properties were evaluated by DSC and TGA. Membranes of the sulfonated copolymers were prepared using the casting method and their IEC evaluated by titration, water uptake (WU) by gravimetry and its electrochemical properties by EIS. Sulfonated membranes were also characterized mechanically by TMA. The sulfonated, non-sulfonated and alkylated copolymers exhibited the vibrational bands and chemical shifts with the signals corresponding to the functional groups associated with the involved comonomers, as well as the sulfonic group. Sulfonated copolymers exhibited an increase in Tg values compared to the non-sulfonated ones in addition to a good thermal stability for the desired application. Sulfonated and alkylated copolymers reduced their complex moduli (E*), but their values depended on the number of carbons in the aliphatic chain. Sulfonated copolymers exhibited high IEC values and a sulfonation degree of 38% was calculated. Proton conductivity for St/VTz-91:8C:S membrane (6.86x10-3 S.cm-1) was close to that obtained for the Nafion 117 membrane (7.6x10-3 S.cm-1). These copolymers are interesting for further investigation for their use as polymeric electrolytes for fuel cells.