Preparation of polymer solid electrolytes from starch

Author(s)

Douglas Cardoso Dragunski

• Document type: Doctoral Thesis
• Press: São Carlos. , gráficos, ilustrações, tabelas.
• Institution: Universidade de São Paulo (USP). Instituto de Química de São Carlos (IQSC/BT)
• Defense date: 2003-03-24

Examining board members

Agnieszka Joanna Pawlicka Maule; Luiz Henrique Capparelli Mattoso; Ernesto Chaves Pereira de Souza

• Advisor: Agnieszka Joanna Pawlicka Maule
• Field of knowledge: Engineering - Materials and Metallurgical Engineering
• Indexed in: Banco de Dados Bibliográficos da USP-DEDALUS
• Location: Universidade de São Paulo. Biblioteca do Instituto de Química de São Carlos; IQSC/T1426

Abstract

This work shows the results of preparation and characterization of solid polymeric electrolytes obtained from physically and chemically modificated amylopectin-rich starch. The physical modifications were performed by plasticization process with different substances, while chemical modifications were performed by grafting with commercial isocyanate [toluene diisocyanate of poly (propylene oxide)] and by sulfatation reactions. With the goal of obtaining new SPEs, the influence of salt quantity and temperature on ionic conductivity was investigated. Ali the samples were characterized by X-ray diffraction, thermal analysis, scanning electronic microscopy and spectroscopy electrochemical impedance measurements. The analysis of the samples with different plasticizers shows, that sorbitol, ethyleneglycol and glycerol, ali containing OH groups, produced better conductivity and stability values than others plasticizers. However, the samples plastificated with 30% of glycerol in mass of amylopectin showed best conductivities values, adherence to the glass, transparence, and stability. The maximum of conductivity (1. 1 x 10-4 Scm-1) for these samples was achieved for the LiCI04 quantity of [O]/[Li] = 6.5. lt was also observed that conductivity as a function of temperatura in ali the plasticized samples displayed Arrhenius behavior. Among different salts, the best conductivity values were obtained with LiBF4 (5.1 x 10-5 Scm-1; [O]/[Li]=10) . Grafting reactions were confirmed by infrared, nuclear magnetic resonance CP/MAS 13C, X-ray diffraction, and scanning electronic microscopy techniques. After the extractive removal and additional lithium salt insertion by diffusion, the ionic conductivity was 3.5 x 10-5 Scm-1 at 30 ºC. These films showed VTF behavior of conductivity as a function of temperature and also good transparency in the visible range of electromagnetic spectra. ln arder to insert negative groups in the polymeric chain, sulfatation reactions of amylopectin were performed. Subsequently, the samples were plastificated with glycerol and lithium salt was added. These samples showed improved conductivity values (9.2 x 10-5 Scm-1) when compared with only plasticized samples (3.3 x 10-5 Scm- 1). These films were homogeneous and opaque. Grafting of these sulfatated samples was also performed, but the ionic conductivity values were inferior compareci to only grafted amylopectin. The results obtained in this work reveal that modification of amylopectin results in the transparent film samples with conductivity values comparable to other ionic conducting systems. Therefore , the amylopectin-rich starch is a very good candidate to obtain new solid polymeric electrolytes that can be used in electrochromic devices such as electrochromic windows. (AU)