Trimethylsilylation of cellulose in ionic liquids.

Macromolecular bioscience (2008-11-26)
Werner Mormann, Markus Wezstein
ABSTRACT

Trimethylsilylation of cellulose in different 1,3-dialkylimidazolium ionic liquids (IL) with hexamethyldisilazane (HMDS) as a silylating agent was investigated. Trimethylsilyl (TMSi) cellulose with a degree of substitution (DS) greater than 1 is insoluble in the IL. The maximum DS obtained depends on the nature of the anion. Carboxylate and diethylphosphate counterions gave better results than chloride or thiocyanate, which corresponds to the solubility of HMDS in the IL. Controlled silylation with stoichiometric amounts of HMDS was feasible in imidazolium carboxylates and diethylphosphate. Analysis of the substitution pattern of the silyl groups in the anhydroglucose unit (AGU) by methylation analysis gave a more homogeneous distribution under (initially) homogeneous conditions (fewer unsubstituted AGUs, fewer trisubstituted AGUs) compared to TMSi cellulose obtained in liquid ammonia.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Hexamethyldisilazane, reagent grade, ≥99%
Sigma-Aldrich
Lithium bis(trimethylsilyl)amide solution, 1.0 M in THF
Sigma-Aldrich
Sodium bis(trimethylsilyl)amide solution, 1.0 M in THF
Sigma-Aldrich
Potassium bis(trimethylsilyl)amide solution, 1 M in THF
Sigma-Aldrich
Lithium bis(trimethylsilyl)amide, 97%
Sigma-Aldrich
Potassium bis(trimethylsilyl)amide, 95%
Sigma-Aldrich
Hexamethyldisilazane, ReagentPlus®, 99.9%
Supelco
Hexamethyldisilazane, for GC derivatization, LiChropur, ≥99.0% (GC)
Sigma-Aldrich
Potassium bis(trimethylsilyl)amide solution, 0.5 M in toluene
Sigma-Aldrich
Lithium bis(trimethylsilyl)amide solution, 1 M in toluene
Sigma-Aldrich
Sodium bis(trimethylsilyl)amide, 95%
Sigma-Aldrich
Lithium bis(trimethylsilyl)amide solution, 1.5 M in THF
Sigma-Aldrich
Hexamethyldisilazane, produced by Wacker Chemie AG, Burghausen, Germany, ≥97.0% (GC)
Sigma-Aldrich
Lithium bis(trimethylsilyl)amide solution, 1.0 M in hexanes
Sigma-Aldrich
Sodium bis(trimethylsilyl)amide solution, produced by Wacker Chemie AG, Burghausen, Germany, 40% in THF
Sigma-Aldrich
Sodium bis(trimethylsilyl)amide solution, 0.6 M in toluene
Sigma-Aldrich
Tris[N,N-bis(trimethylsilyl)amide]yttrium
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Tris[N,N-Bis(trimethylsilyl)amide]gadolinium(III), 98%
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Lithium bis(trimethylsilyl)amide solution, 1 M in tert-butyl methyl ether
Sigma-Aldrich
Potassium bis(trimethylsilyl)amide solution, 1.0 M in methyl tert-butyl ether
Sigma-Aldrich
Tris[N,N-bis(trimethylsilyl)amide]samarium(III), 98%
Sigma-Aldrich
Tris[N,N-bis(trimethylsilyl)amide]europium(III), 98%
Sigma-Aldrich
Lithium bis(trimethylsilyl)amide solution, 0.5 M in 2-methyltetrahydrofuran
Sigma-Aldrich
Potassium bis(trimethylsilyl)amide solution, 1.0 M in 2-methyltetrahydrofuran
Sigma-Aldrich
Sodium bis(trimethylsilyl)amide solution, 0.5 M in methyl tert-butyl ether
Sigma-Aldrich
Lithium bis(trimethylsilyl)amide solution, 0.5 M in toluene
Sigma-Aldrich
Tris[N,N-bis(trimethylsilyl)amide]yttrium, packaged for use in deposition systems