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Synthesis and structure/property relationships of regioselective 2-O-, 3-O- and 6-O-ethyl celluloses. 2010

Hiroshi Kamitakahara, and Toshihiro Funakoshi, and Shinji Nakai, and Toshiyuki Takano, and Fumiaki Nakatsubo
Graduate School of Agriculture, Kyoto University, Kitashirakawa-oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan. hkamitan@kais.kyoto-u.ac.jp

Regioselectively ethylated celluloses, 2-O- (1), 3-O- (2), and 6-O-ethyl- (3) celluloses were synthesized via ring-opening polymerization of glucopyranose orthopivalate derivatives. The number-average degrees of polymerization (DP(n)s) of compounds 1 and 2 were calculated to be 10.6 and 49.4, respectively. Three kinds of compound 3 with different DP(n)s were prepared: DP(n)s = 12.9 (3-1), 60.3 (3-2), and 36.1 (3-3). The 2-O-, 3-O-, and 6-O-ethylcelluloses were soluble in water, confirmed by NMR analysis. Furthermore, the 3-O- (2), and 6-O-ethyl- (3-2) celluloses showed thermo-responsive aggregation behavior and had a lower critical solution temperature (LCST) at about 40 degrees C and 70 degrees C, respectively, based on the results from turbidity tests and DSC measurements. The 6-O-ethyl-cellulose (3-3) with DP(n) = 36.1 and DP(w) = 54.6 showed gelation behavior over approx 70 degrees C, whereas the 6-O-ethyl-celluloses 3-1 and 3-2 with lower and higher molecular weight, such as DP(n)s 12.9 and 60.3, did not show gelation behavior at this temperature. It was revealed that the position of ethyl group affected the phase transition temperature. According to our experiments, the 3-O-ethyl and 6-O-ethyl groups along the cellulose chains caused the thermo-responsive property of their aqueous solutions. The appropriate DP of the regioselective 6-O-ethyl-cellulose existed for gelation of the aqueous solution.

UI MeSH Term Description Entries
D009682 Magnetic Resonance Spectroscopy Spectroscopic method of measuring the magnetic moment of elementary particles such as atomic nuclei, protons or electrons. It is employed in clinical applications such as NMR Tomography (MAGNETIC RESONANCE IMAGING). In Vivo NMR Spectroscopy,MR Spectroscopy,Magnetic Resonance,NMR Spectroscopy,NMR Spectroscopy, In Vivo,Nuclear Magnetic Resonance,Spectroscopy, Magnetic Resonance,Spectroscopy, NMR,Spectroscopy, Nuclear Magnetic Resonance,Magnetic Resonance Spectroscopies,Magnetic Resonance, Nuclear,NMR Spectroscopies,Resonance Spectroscopy, Magnetic,Resonance, Magnetic,Resonance, Nuclear Magnetic,Spectroscopies, NMR,Spectroscopy, MR
D002482 Cellulose A polysaccharide with glucose units linked as in CELLOBIOSE. It is the chief constituent of plant fibers, cotton being the purest natural form of the substance. As a raw material, it forms the basis for many derivatives used in chromatography, ion exchange materials, explosives manufacturing, and pharmaceutical preparations. Alphacel,Avicel,Heweten,Polyanhydroglucuronic Acid,Rayophane,Sulfite Cellulose,alpha-Cellulose,Acid, Polyanhydroglucuronic,alpha Cellulose
D005782 Gels Colloids with a solid continuous phase and liquid as the dispersed phase; gels may be unstable when, due to temperature or other cause, the solid phase liquefies; the resulting colloid is called a sol.
D012995 Solubility The ability of a substance to be dissolved, i.e. to form a solution with another substance. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed) Solubilities
D012996 Solutions The homogeneous mixtures formed by the mixing of a solid, liquid, or gaseous substance (solute) with a liquid (the solvent), from which the dissolved substances can be recovered by physical processes. (From Grant & Hackh's Chemical Dictionary, 5th ed) Solution
D044366 Transition Temperature The temperature at which a substance changes from one state or conformation of matter to another. Temperature, Transition,Boiling Point Temperature,Freezing Point Temperature,Melting Point Temperature,Boiling Point Temperatures,Freezing Point Temperatures,Melting Point Temperatures,Temperature, Boiling Point,Temperature, Freezing Point,Temperature, Melting Point,Temperatures, Boiling Point,Temperatures, Freezing Point,Temperatures, Melting Point,Temperatures, Transition,Transition Temperatures
D044367 Phase Transition A change of a substance from one form or state to another. Gas-Liquid-Solid Phase Transitions,Sol-Gel Phase Transition,Gas Liquid Solid Phase Transitions,Gas-Liquid-Solid Phase Transition,Phase Transition, Gas-Liquid-Solid,Phase Transition, Sol-Gel,Phase Transitions,Phase Transitions, Gas-Liquid-Solid,Phase Transitions, Sol-Gel,Sol Gel Phase Transition,Sol-Gel Phase Transitions,Transition, Gas-Liquid-Solid Phase,Transition, Sol-Gel Phase,Transitions, Gas-Liquid-Solid Phase,Transitions, Sol-Gel Phase

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