Influence of the supramolecular structure and physicochemical properties of cellulose on its dissolution in a lithium chloride/N,N-dimethylacetamide solvent system.
The present work deals with the effects of structural variables of celluloses on their dissolution in the solvent system LiCl/N,N-dimethylacetamide, LiCl/DMAc. Celluloses from fast growing sources (sisal and linters), as well as microcrystalline cellulose (avicel PH-101) were studied. The following structural variables were investigated: index of crystallinity, I(c); crystallite size; polymer porosity; and degree of polymerization determined by viscosity, DPv. Mercerization of fibrous celluloses was found to decrease DPv, I(c), the specific surface area, and the ratio pore volume/radius. The relevance of the structural properties of cellulose to its dissolution is discussed. Rate constants and activation parameters of cellulose decrystallization, prior to its solubilization, have been determined under nonisothermal conditions. The kinetic parameters calculated showed that dissolution is accompanied with small, negative enthalpy and a large, negative entropy of activation.
Ramos
Ludmila A
LA
Instituto de Química de São Carlos, Universidade de São Paulo, C P 780, 13 560 970, São Carlos, SP, Brazil.
Assaf
José M
JM
El Seoud
Omar A
OA
Frollini
Elisabete
E
D000081:Acetamides / Q000737:chemistry*; D000327:Adsorption; D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry*; D002417:Cattle; D002482:Cellulose / Q000737:chemistry*; D002845:Chromatography; D002851:Chromatography, High Pressure Liquid; D003432:Cross-Linking Reagents / Q000737:chemistry; D019277:Entropy; D006358:Hot Temperature; D006838:Hydrocarbons / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007262:Infusions, Intravenous; D007700:Kinetics; D018021:Lithium Chloride / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D008956:Models, Chemical; D009584:Nitrogen / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D051381:Rats; D012997:Solvents; D013053:Spectrophotometry; D019802:Succinic Acid / Q000737:chemistry; D013997:Time Factors; D014357:Trypsin / Q000737:chemistry; D014466:Ultraviolet Rays; D014961:X-Ray Diffraction
D000081:Acetamides; D001672:Biocompatible Materials; D003432:Cross-Linking Reagents; D006838:Hydrocarbons; D011108:Polymers; D012997:Solvents; C030011:carbene; D011092:Polyethylene Glycols; D002482:Cellulose; D019802:Succinic Acid; D014357:Trypsin; D018021:Lithium Chloride; C013959:dimethylacetamide; D009584:Nitrogen; D008697:Methane