DEVELOPMENT OF IONIC CONDUCTIVE CELLULOSE MAT BY SOLUTION BLOW SPINNING AND LASER-INDUCED GRAPHENE FROM PINEAPPLE NANOCELLULOSE FOR USE IN FLEXIBLE ELECTRONIC DEVICES

In the face of environmental issues and aiming at electronic devices of rapid production at low cost, this doctoral thesis proposed two new and innovative approaches to obtain substrates, dielectrics, and electrodes from a single biopolymer: cellulose. In a first moment, a simple approach to produce low-cost flexible ionic conductive cellulose mats (ICCMs) using solution blow spinning (SB-Spinning) is reported. The electrochemical properties of the ICCMs were adjusted through infiltration with alkali hydroxides (LiOH, NaOH, or KOH), which enabled of ICCMs application as dielectric and substrate in oxide-based field effect transistors (FETs) and pencil-drawn resistorloaded inverters. The FETs showed good electrical performance under operating voltage <2.5 V, which was strictly associated with the type of alkali ion incorporated, presenting satisfactory performance for the ICCM infiltrated with K+ ion. The inverters with K+ ions also presented good dynamic performance, with a gain close to 2. Regarding the cellulose-based electrodes, a second innovative approach is reported to synthetize laser-induced graphene (LIG) structures from carboxymethyl cellulose (CMC)-based ink containing LIG obtained from cellulose nanocrystals (CNCs) extracted from pineapple leaf fibers (PALFs). To prove this concept, zinc oxide ultraviolet (ZnO UV) sensors were designed varying the amount of LIG from CNCs. Sensor obtained from LIG written directly on paper substrate were also performed. The ZnO UV sensors designed with CMC-based ink showed responsivity 40-fold higher than that of paper direct-written LIG, as well as excellent electrical performance under flexion. These findings may open new promising possibilities for low-consumption wearable electronics, allowing the use of concepts such as the "Internet of Things" and opening the possibility of generating 100% organic cellulose-produced electronic devices.Frente às questões ambientais e visando dispositivos eletrônicos de rápida produção e baixo custo, este projeto de pesquisa de doutorado propôs duas abordagens inovadoras para a obtenção de substratos, materiais dielétricos e eletrodos a partir de um único biopolímero: a celulose. Em um primeiro momento relata-se uma abordagem simples para produzir mantas condutoras iônicas de celulose (ICCM) flexíveis aplicando fiação por sopro em solução (SB-Spinning) seguido da infiltração com hidróxidos alcalinos (LiOH, NaOH ou KOH), permitindo sua aplicação como dielétrico e substrato em transistores e inversores com resistor desenhado a lápis. Os transistores exibiram um bom desempenho sob tensão de operação abaixo de 2,5 V, apresentando desempenho satisfatório para as mantas infiltradas com K+, além do inversor apresentar um ganho próximo de dois. Visando também eletrodos oriundos da celulose, este projeto relatou uma abordagem inovadora para sintetizar grafeno induzido por laser (LIG) a partir de tinta à base de carboximetilcelulose (CMC) contendo LIG obtido de nanocristais de celulose (CNCs) do abacaxi. Como prova de conceito, sensores de ZnO UV foram projetados variando a quantidade de LIG dos CNCs na tinta a base de CMC, assim como sensores obtidos por escrita direta de LIG em substrato de papel. Os sensores de ZnO UV flexíveis formulados com tinta apresentaram responsividade 40 vezes maior que os sensores contendo LIG direto do papel. Essas descobertas podem inaugurar uma nova Era na geração de eletrônicos vestíveis de baixo consumo, permitindo conceitos como "Internet das Coisas", e abrindo a possibilidade de dispositivos 100% orgânicos oriundos da celulose

Cellulose nanocrystals and nanofibrils films of eucalyptus and pineapple (curauá) by continuing casting

New materials from cellulose have been developed, such as cellulose nanocrystals (CNC) and cellulose nanofibrils (CNF). Different morphologies of the cellulose can lead to the formation of films with different thermal, mechanical and optical properties in relation to conventional cellulose films. The objective of this work was to evaluate the effect of different dimensional scales of cellulose, micro and nanometric, on the production of cellulose films from two vegetable species and their thermal, mechanical, morphological and optical properties. Eucalyptus fibers and pineapple leave fiber (curauá) (PALF) were used as cellulosic fibers for this study. The films of eucalyptus and pineapple cellulosic fibers were prepared by filtration and casting, and the CNC and CNF films were obtained by continuous casting. The CNC and CNF films showed mechanical tensile strength in the order of 9 to 35 MPa higher than the films of cellulose fibers, regardless of the origin of the fiber. The continuous casting process produced CNC and CNF films that presented different mechanical resistance in the longitudinal direction of the process with respect to the transverse direction. This behavior may be related to how hydrogen bonds and mechanical anchorages occur between nanofibers. The thermal stability of the nanocellulose films was lower in the order of 20 to 150 ºC than in the films of fibers due to the routes of obtaining the CNC and CNF. Nanofiber films presented lower opacity in the order of 3 to 60% lower than the films of fibers due to the diameter of the nanocelluloses. Curauá fibers had the highest crystallinity index (Ic) reaching 87%. It is concluded that the properties studied were influenced by the type of nanocellulose (CNC or CNF), the origin of the cellulose (eucalyptus or pineapple), and the micro and nanometric scale of the fibers.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Novos materiais a partir da celulose tem sido obtidos, como os nanocristais de celulose (CNC) e as nanofibrilas de celulose (CNF). Diferentes morfologias da celulose podem levar a formação de filmes com propriedades térmicas, mecânicas e ópticas diferentes de filmes de celulose convencional. O objetivo deste trabalho foi avaliar o efeito de diferentes morfologias de fibras de celulose, micro e nanométricas, na obtenção de filmes - provenientes de duas espécies vegetais – e em suas propriedades térmicas, mecânicas, ópticas e morfológicas. Utilizou-se como fibras celulósicas para este estudo as fibras de eucalipto e fibras de folhas de abacaxi (curauá) (PALF). Os filmes de fibras celulósicas de eucalipto e de abacaxi foram confeccionados por filtragem e casting, e os filmes de CNC e CNF foram obtidos por continuous casting. Os filmes de CNC e CNF apresentaram resistência mecânica à tração, na ordem de 9 a 35 MPa superior aos filmes de fibras de celulose, independente da origem da fibra. O processamento por continuous casting produziu filmes de CNC e CNF que apresentaram resistência mecânica diferente no sentido longitudinal ao processo com relação ao sentido transversal. Este comportamento pode estar relacionado de que forma ocorrem às ligações de hidrogênio e os emaranhamentos mecânicos entre as nanofibras. A estabilidade térmica dos filmes de nanofibra foi menor na ordem de 20 a 150 ºC do que aos filmes de fibras devido às rotas de obtenção das CNC e CNF. Os filmes de nanofibra apresentaram menor opacidade, na ordem de 3 a 60% inferior, que os filmes de fibras devido ao diâmetro das nanofibras. As fibras de curauá apresentaram o maior índice cristalinidade (Ic) chegando a 87%. Conclui-se que a propriedades estudadas foram influenciadas pelo tipo de nanofibra (CNC ou CNF), pela origem da celulose (eucalipto ou abacaxi), e pela escala micro e nanométrica das fibras

Thermoplastic Waxy Starch Films Processed by Extrusion and Pressing: Effect of Glycerol and Water Concentration

<div><p>Thermoplastic starch properties depends of plastification process. The aim of this study was to analyze the effect of concentration of glycerol and water on plastification, glass transition temperature (Tg) and tensile properties of thermoplastic waxy starch (TPWS). Formulations were extruded in the following concentrations of starch/glycerol/water: 70/30/0 (TPWS 0%); 70/25/5 (TPWS 5%); 70/20/10 (TPWS 10%) weight percentage. Crystalline peaks in WAXS diagrams and native grains present in SEM micrographs showed that the TPWS 0% and 5% were not sufficient to promote total plastification of the waxy starch, and TPWS 10% showed the higher starch plastification. Tg measurements by DMTA were 30 ºC to TPWS 0%, 23 ºC to TPWS 5% and 40 ºC to TPWS 10%. These results showed that glycerol and water had effect plasticizer in TPWS 5% and antiplasticizer in TPWS 10%. Mechanical tensile results showed that higher tensile strength was observed in the systems with more effective starch plastification.</p></div