Banca de DEFESA: ELIAS JANUÁRIO DE LIMA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : ELIAS JANUÁRIO DE LIMA
DATA : 11/08/2017
HORA: 14:30
LOCAL: anfiteatro B do CCET
TÍTULO:

SYNTHESIS OF POLYMER ELECTROLYTES BASED ON POLYMER BLENDS OF PEO/NaAlg MODIFIED WITH LiClO₄

PALAVRAS-CHAVES:

Polymer Membranes. Crystallinity. Ion conductivity. Electrochemical impedance. Solid polymer electrolytes.

PÁGINAS: 101
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Físico-Química
ESPECIALIDADE: Eletroquímica
RESUMO:

The investigation of salt-modified polymer blends has been an alternative area in the field of research of new materials, since modified blends may have better properties than pure polymers. In the present research was performed to study the membranes based on blends of poly (ethylene oxide) (PEO) and sodium alginate (NaAlg) (PEO: NaAlg): 20%:80% (P20), 40%:60% (P40), 60%:40% (P60), 80%:20% (P80). These blends were modified by the addition of  0.5 mL of lithium perchlorate (LiClO₄) obtaining the solid polymer electrolytes, POE:NaAlg:LiClO₄ - 20%:80%:0.5 mL (P20S) 40%:60%:0.5 mL (P40S), 60%:40%:0.5 mL (P60S), 80%:20%:0.5 mL (P80S). The membranes were characterized by electrochemical impedance (EIS), thermal analysis: differential scanning calorimetry (DSC) and thermogravimetry (TG), infrared spectroscopy in the mode of attenuated total reflectance (FTIR-ATR), X-ray diffraction (DRX) and scanning electron microscopy (SEM). All analyzes carried by EIE of the membranes NaAlg, P20, P40, P60, P80, P20S, P40S, P60S and P80S showed the trend of form a semicircle. While the PEO has two semicircles, the first semicircle has a maximum imaginary impedance (Z'') at frequency ν_max = 213.51 Hz. This behavior may be related to the conduction process in the bulk of the polymer membranes. This behavior may be related to the conduction process in the bulk of the polymer membranes. From the adjustment of the semicircle, the ohmic resistance (R_Ω), polarization resistance (R_p) and the frequency at the maximum peak (ν_max) were obtained. From these data and using some mathematical equations, the double layer capacitance (C_dc) and the ionic conductivity (σ) were obtained. It was observed that the addition of NaAlg in the polymer system altered the resistive property of PEO. This is confirmed when comparing the ionic conductivities of PEO and P20 membranes which are, respectively, 8.59 x 10^-10 S.cm^-1 and 9.45 x 10^-6 S.cm^-1.  Being P20, among all the studied systems without addition of salt, the one that presented greater ionic conductivity. By adding 1% of LiClO₄, P20S membrane, a change of one order of magnitude was observed in ionic conductivity (σ = 2,45x10^-5 S.cm^-1) compared to P20 (σ = 9.45 x10^-6 S.cm^-1). Among all the membranes studied, the one with the highest ionic conductivity was P20S. The data obtained by DSC showed that the crystallinity of the PEO was reduced, proportionally, with the increase of the NaAlg ratio in the membranes, that is, with the addition of NaAlg in the membranes. However, addition of the salt reduces the crystallinity of P80S relative to P80, with crystallinity (X_c) values being respectively 49.6 % and 72.1 %. The data obtained by TG showed that the addition of the salt in the P40 membrane was more effective in increasing the thermal stability of this membrane (P40S) since the second stage of the thermal degradation of P40 starts at 160 °C, whereas in the P40S it starts in 200 °C. The FTIR-ATR spectra showed that physical interactions occur between the polymers, that is, in the blends, because there is a variation of the intensity of the bands (1600 and 1410 cm^-1) in relation to those in the pure polymers. The micrographs obtained by MEV showed that the two polymers have different morphological surfaces. However, in the membranes: P20S, P40S, P60S and P80S variations were observed in the morphological aspect, because they present surfaces with profile of deformed spherulites. This behavior suggests the reduction of the crystalline phases of the membranes studied.

MEMBROS DA BANCA:
Interno - 1645110 - CARLOS ALBERTO MARTINEZ HUITLE
Presidente - 348475 - DJALMA RIBEIRO DA SILVA
Externo à Instituição - JOSE ALZAMIR PEREIRA DA COSTA - UERN
Interno - 1958858 - LUIZ HENRIQUE DA SILVA GASPAROTTO
Externo ao Programa - 1149539 - MARIA GORETTE CAVALCANTE
Externo à Instituição - ROBERTA PATRÍCIA MEDEIROS DE MARIA - EEDNM