Synthesis of celulose decorated eith a merocyanine polarity probe: relevance to the derivatization of the biopolymer

• Grant number: 17/03887-7
• Support Opportunities: Scholarships abroad - Research Internship - Scientific Initiation
• Start date: April 27, 2017
• End date: August 26, 2017
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Organic Chemistry
• Principal Investigator: Omar Abou El Seoud
• Grantee: Jessica Carol de Jesus
• Supervisor: Thomas Heinze
• Host Institution: Instituto de Química (IQ). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: Friedrich Schiller University Jena, Germany
• Associated to the scholarship: 16/13932-7 - Solvation in ionic liquids-molecular solvents binary mixtures: effects of the mixture composition and temperature, and applicability on cellulose dissolution, BP.IC

Abstract

Due to the presence of strong inter- and intramolecular hydrogen bonds between its hydroxyl groups, cellulose is a semi-crystalline biopolymer with highly ordered and amorphous regions. Disruption of these hydrogen bonds is important for the swelling, dissolution, and derivatization of this biopolymer. Most cellulose derivatives, in particular its esters and ethers, are prepared industrially by heterogeneous scheme involving reaction of the swollen biopolymer with the derivatizing bath, e.g., acetic anhydride/acetic acid/mineral acid catalyst. Cellulose is also derivatized under homogeneous reaction conditions. In this case, the biopolymer is treated with a solvent or solvent mixture that disrupts the hydrogen bonding present, leading to its dissolution. Examples of solvents for cellulose are strong electrolytes in dipolar aprotic solvents, DAP, ionic liquids, ILs, and mixtures ILs-DAPs. Therefore, understanding cellulose-solvent Interactions is important both industrially and scientifically. Information about the interactions of cellulose with the solvent can be obtained by use of the so-called solvatochromic probes. These are compounds whose spectra are sensitive to the properties of pure solvents, composition of mixed solvents, and the temperature. When these probes are used to examine a cellulose solution, the information about solvent-biopolymer interactions is indirect/overall because the site(s) of the probe in the medium (bulk solvent; biopolymer interface) is not determined. A much better approach is to "anchor" the solvatochromic probe covalently to the surface of cellulose. This insures that the probe is reporting a property, e.g., empirical polarity at the surface of the dissolved biopolymer. The present project aims the synthesis of hydroxyethyl cellulose decorated with a merocyanine derivative and its study for determining empirical polarity. Shortly, the covalent bonding of the probe gives more precise information about local solvent composition and specific interactions at the biopolymer surface. This can be employed to understand the efficiency of binary solvent mixtures as solvents for cellulose. (AU)