Polymerization of levoglucosan

Investigation of the polymerization of levoglucosan at various temperatures and pressures led to the conclusion that dimers, tetramers, hexamers, and octamers are formed. One preparation was shown to contain approximately 2% of a nondialyzable fraction.209... 

In a series of papers commencing in 1959, Schuerch and coworkers have reported their extensive examination of the polymerization of levo-glucosan113 214 and several of its derivatives,215 and of 1,6-anhydro-/3-D-galactopyranose24 (o-galactosan) and its 2-methyl ether.24 Preliminary experiments on the polymerization of levoglucosan were conducted under diminished pressure over a temperature range of 100-130°, using several acidic catalysts—formic, acetic, monochloroacetic, phosphoric, and hydrochloric acids,214 and zinc chloride—in various mole ratios of catalyst to... 

In considering the possible origin and precursors of the charred residue, it should be noted that pyrolysis of levoglucosan (in helium) leaves a small amount of char. In view of the well established, catalytic polymerization of levoglucosan, - the polymerization and... 

Endeavors to achieve technical utilization led to co-polymerization of levoglucosan (6) with various alcohols600-602 and ethers.592,603-610 Even though the structures of the resins obtained are not exactly... 

The first successful polymerizations were obtained in solution, with cationic initiators, under conditions typical of ring-opening polymerization. Bredereck and Hutten polymerized the perbenzyl ether and peracetate of levoglucosan, using, as initiators, various carbonium ions formed in situ from organic halides and silver perchlorates. The products were apparently not stereoregular, but were definitely poly-... 

No triester of levoglucosan was found92 that polymerized at temperatures much below 0°. At —78°, the triacetate complexed with phosphorus pentafluoride, and, at high concentration, precipitated from solution.91 The tris(monofluoroacetate) failed to polymerize under a variety of conditions.91 The trinitrate polymerized at 0°, but the product was not fully characterized.92 Polymerization of the triacetate proceeded to reasonable conversions with a number of catalysts at 0°, but the viscosity and the stereoregularity of these polymers were low.92 In a simple, copolymerization experiment, it was demonstrated that the low polymerizability of levoglucosan triacetate was due not only to a failure to initiate but also to sluggish propagation.92... 

The Latvian school has continued its active research on the polymerization and application of levoglucosan and its derivatives. The main thrust of their research has been in the utilization of levoglucosan in commercial resins and polymers. A substantial part of that re-... 

Abe and Prins214 suggested that the first step in the polymerization reaction of levoglucosan consists of a dimerization of all of the levoglucosan units. This involves the opening of all 1,6-anhydro rings, followed by the formation of a reactive, (1— 6)-linked intermediate (52), which polymerizes... 

This mechanism implies that a portion of the charred residue from the pyrolysis of cellulose could be derived from the secondary reactions involved in the decomposition of levoglucosan. In the production of levulinic acid, about 25 % of the initial D-glucose residues is converted into the humin that separates as an insoluble, charred residue. This humin could be formed from 5-(hydroxymethyl)-2-furaldehyde, which is readily polymerized and decomposed on heating under acid conditions. The kinetic investigations indicate that the humin could also be formed from the reaction of 5-(hydroxy-methyl)-2-furaldehyde with one of its precursors. ... 

Polymerization of the sugars such as levoglucosan into thermoplastics... 

In degree of polymerization (DP) studies of borax treatments and ammonium dihydrogen orthophosphate (53), cellulose treated with the acid charred and depolymerized very rapidly. Its DP value decreased from 1110 to 650 after only 2 min of heating at 150 °G. Gellulose treated with borax showed a DP reduction from 1300 to 700 after 1 h of heat treatment at 150 °G. Both these compounds catalyzed the suppression of levoglucosan formation but they had different effects on the chain depolymerization reaction (53). 

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