Investigations on esterification reactions of starches in 1‐N‐butyl‐3‐methylimidazolium chloride and resulting substituent distribution

Abstract

The ionic liquid (IL) 1-N-butyl-3-methylimidazolium chloride ([C 4 mim] þ Cl À ) was used as solvent for different esterification reactions of the biopolymer starch. Therefore, maize starches with varying content of amylose were used. Different carboxylic acid anhydrides were applied to esterify starch with a degree of substitution (DS) in the range of 0.7-3.0. For example, starch acetates with the mentioned DS are accessible within 30 min at a 105 C-reaction temperature. The DS distribution of starch acetates synthesized in IL was compared with the common starch acetate synthesis of Mark and Mehltretter. Also, a consideration of starch acetates and cellulose acetates synthesized in [C 4 mim] þ Cl À is given. The starch esters were characterized by means of Raman spectroscopy for qualitative-and nuclear magnetic resonance spectroscopy for quantitative determination of the functionalization pattern. Moreover, the molecular mass distribution was determined after saponification by means of GPC-MALLS.

Dissolution of starch in urea/NaOH aqueous solutions

“…used ionic liquids as solvents for chemical modifications of starch. From then on, more and more studies on ionic liquids used as solvents for starch were reported . However, the facts that the solubility depends on structure of ionic liquids, together with high temperature needed and high cost, greatly restrain their applications in starch industry.…”

Effects of ionic liquid 1-allyl-3-methylimidazolium chloride treatment on the microstructure and phase transition of cornstarch

“…Over the past decade, researchers have reported that starch can be dissolved or plasticized by ILs including 1-allyl-3-methylimidazolium chloride (AMIMCl) (Wang et al, 2009a,b;Wilpiszewska and Spychaj, 2011), 1-butyl-3-ethylimidazolium chloride (BMIMCl) (Lehmann and Volkert, 2009;Liu et al, 2005) and 1-ethyl-3-methylimidazolium acetate (EMIMAc) Budtova, 2013 2013). They found that these liquids disrupt the hydrogen bonding between the hydroxyl groups of starch and damage the original semi-crystalline region, leading to starch dissolution.…”

Modification of starch by graft copolymerization

“…Native starch displays high water sensitivity and lack of mechanical strength. Starch can be plasticized to some degree with plasticizer such as water, polyols (glycerol , glycols , xylitol ), amides , or ionic liquids notably. Plasticized starch is biodegradable and is used for packaging and agricultural purposes.…”