SYNTHESIS AND CHARACTERIZATION OF NANOCRYSTALLINE CELLULOSE FROM BACTERIAL CELLULOSE AND ITS NANOCOMPOSITES WITH POLY(ETHYLENE OXIDE) AS POLYMER ELECTROLYTE MEMBRANES

• Main Author: ANWAR NIM:30512015, BUDIMAN
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/26163
• Institution: Institut Teknologi Bandung

The limited availability of non-renewable and unsustainable resources of material and environmental damage caused during the production of these materials and post-use, led researchers to develop renewable, sustainable, eco-friendly, biocompatible, and low-cost natural materials. Nanocrystalline cellulose (CNC) is one of the excellent nanomaterials that meet all of these criteria and is being currently developed. CNC was extracted from various sources of cellulose by removing the amorphous part. The use of bacterial cellulose (BC) as a cellulose source to obtain CNC has some features, i.e. BC is a relatively pure cellulose source and its synthesis process can utilize various waste that pollutes the environment as a culture medium. One of the application of CNC is as a reinforcing nanofiller in a polymer electrolyte matrix. The performance of CNC as reinforcing nanofiller is terribly influenced by morphology and properties of CNC. The morphology and properties of CNC are highly dependent on the source of cellulose. Therefore, the aims of this study are to obtain CNC from a low-cost and environmentally friendly source as well as to investigate its properties to be utilized in various purposes, one of which is as reinforcing nanofiller in the polymer electrolyte matrix. BC that obtained by using pineapple peel waste juice as a culture medium is used as the source of cellulose. <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> The first stage of work was the preparation of BC by Gluconacetobacter xylinum by using pineapple peel waste juice as a culture medium with fermentation time for 14 days. The yield obtained was 3.8 g/L, this yield is higher than the result obtained by using more high-cost conventional medium. The results of FTIR and thermogravimetric analysis show that BC contains non-cellulosic protein material of about 19%. FTIR and XRD analysis provides the information that BC has a mixture of parallel cellulose I and antiparallel chain-folded cellulose II polymorphic structure. The crystallinity ratio (CrR), hydrogen bonding energy (EH), and the distance between the hydrogen bonds (RH) of BC obtained from the FTIR analysis were 0.829, 21.57 kJ and 2.784 Å, respectively. The crystallite size (L) and the crystallite interior chains (X) of BC obtained from the XRD analysis were 8.769 nm and 0.76, respectively. The analysis of SEM image shows that the morphology of BC is a mixture of ribbon-like microfibril of cellulose I with an average diameter of 52 nm and band-like of cellulose II. The thermal properties and stability of BC were studied with TGA and DTG, BC had thermal degradation at 234, 294, and 448 (rumus)C which indicated the degradation of non-cellulosic material, cellulose and carbonaceous residues, respectively. Furthermore, the obtained BC is used as a cellulose source to obtain CNC. <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> Isolation of CNC from BC includes sulfuric acid hydrolysis, centrifugation, analysis, and sonication processes. Conditions optimization of CNC isolation from BC was done by varying the concentration of sulfuric acid, time and temperature of hydrolysis. The optimal conditions of isolation were obtained at the concentration of sulfuric acid by 50%, the hydrolysis temperature at 50 (rumus)C and hydrolysis time ranging 25 (rumus) 40 minutes with yield ranging 40 (rumus) 60%. FTIR and XRD analysis give the information that CNC have a polymorphic structure of cellulose I, more specifically an allomorphic structure of monoclinic cellulose (rumus). The crystallinity ratio (CrR), hydrogen bonding energy (EH), and the distance between hydrogen bonds (RH) of CNC obtained from FTIR analysis were 0.965, 21.72 kJ and 2.783 Å, respectively. The crystallinity index (CrI), crystallite size (L), and the crystallite interior chains (X) of CNC obtained from XRD analysis were 88%, 14.89 nm and 0.85, respectively. The values of CrR, EH, R, L, and X indicate that CNC have a degree of crystallinity greater than BC origin. The hydrodynamic diameter of CNC particles obtained by dynamic light scattering (DLS) method is in the range of 41 (rumus) 63 nm. The analysis of TEM image shows that CNC have the morphology of needle-like structure with average length and diameter of 325 nm and 25 nm, respectively, with an average aspect ratio (L/D) about 13. The results of TGA and DTG give the information that CNC start to decompose at a temperature of 249 (rumus)C with a thermal degradation peak at 280 and 461 (rumus)C which corresponds to the degradation of cellulose and carbonaceous residues, respectively. The obtained CNC was then used as the reinforcing nanofiller in the production of the nanocomposite polymer electrolyte membranes. <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> Synthesis of nanocomposite polymer electrolyte membranes were performed by solvent casting method using water as a solvent. The characterization of the nanocomposite polymer electrolyte membranes includes ionic conductivity by EIS, the surface and cross-sectional morphology by SEM, functional group analysis and crystallinity by FTIR, degree of crystallinity and thermal properties by DSC, mechanical properties by tensile testing apparatus, and thermal stability by TGA. The incorporation of CNC into the PEO matrix lead the morphology of both cross-section and surface membrane to be more tidy. In contrast, the addition of LiClO4 into the PEO matrix causes the morphology of both cross-section and surface membrane to become ragged. The incorporation of CNC to PEO-LiClO4 causes the morphology of both cross-section and surface membrane to become more chaotic and porous. The crystallinity degree of the membrane increases as the CNC incorporation to the PEO matrix, whereas the addition of LiClO4 into the PEO matrix decreases the crystallinity degree of the membrane. The incorporation of the CNC into PEO-LiClO4 decreases the crystallinity degree of the membrane significantly. The morphology and degree of crystallinity greatly influences the elasticity modulus of membrane. The membrane having a high elasticity modulus is associated with more higher in morphology regularity and degree of crystallinity. The increasing of both amorphous region and elasticity of the PEO-LiClO4/CNC membrane leads the increasing of ionic conductivity up to four times. Moreover, the incorporation of CNC into the PEO-LiClO4 could muffle the explosive decomposition as a result of the destabilitation effect of LiClO4 and increasing the thermal stability of the membrane above 320 (rumus)C. The optimal composition of the PEO-LiClO4/CNC nanocomposite polymer electrolyte membrane that obtained from this study was a molar ratio O/Li of 20 and CNC content of 5%. The characteristics of the PEO-LiClO4/CNC nanocomposite polymer electrolyte membrane at optimum composition was ionic conductivity of 8.35 (rumus) (rumus)4 S/cm; melting and crystallization point at 73.8 (rumus)C and 16.0 (rumus)C, respectively; and elasticity modulus of 10.3 MPa. Therefore, the CNC from a low-cost and environmently friendly source can be used as reinforcing nanofiller in PEO-LiClO4 based polymer electrolyte membrane. <br />