Cyclic Carbonates as Safe and Versatile Etherifying Reagents for the Functionalization of Lignins and Tannins

Abstract

The potential of cyclic carbonates for the functionalization of lignins and condensed tannins was studied in detail. Four different cyclic carbonates, namely, ethylene, propylene, vinyl ethylene, and glycerol carbonates, were evaluated. Full conversion of the phenolic hydroxyl groups was observed within very short reaction times (less than 2 h and as low as 15 min with ethylene carbonate). Comparison among the different cyclic carbonates shows that the substituent influences the reactivity as follows: CH3 < CHCH2 < CH2OH < H. The developed method is a safe alternative to the use of organohalides or epoxides for the introduction of functional groups of interest onto lignins and tannins. The prepared derivatives expose primary or secondary hydroxyl groups, vinyl groups, 1,2- and 1,3-diols, or five-membered cyclic carbonates. All of the derivatives have an enhanced thermal stability and a lowered glass transition temperature (T g) compared to the neat lignins and condensed tannins and thus present a high potential for the preparation of various types of biobased and aromatic polymers. The proposed method also allows the grafting of oligomeric chains when the reaction time is extended and thus represents an alternative to the use of the toxic and hazardous ethylene or propylene oxides for the oxyalkylation of polyphenols.

Epoxidized soybean oil cured with tannic acid for fully bio-based epoxy resin

“…Many chemical modications of lignin and TA have been described for these purposes. [37][38][39] As a type of biobased polyphenol, TA has abundant reactive terminal phenolic hydroxyl groups with a hyperbranched aromatic/alicyclic polyester core, which can make up for the exible chain defects of ESO and form highly crosslinked networks. The chemical formula for commercial TA is oen given as C 76 H 52 O 46 , which corresponds with decagalloyl glucose, 40 as shown in Scheme 1.…”

Mild and controlled lignin methylation with trimethyl phosphate: towards a precise control of lignin functionality

“…Acetylation of lignins was performed according to a protocol previously described. 32 Briefly, 100 mg samples were dissolved in 2 mL pyridine/acetic anhydride (1 : 1 v/v) and stirred at room temperature for 24 h. The mixture was then precipitated in about 50 mL water previously acidified to pH 2 by the addition of a 2 M HCl solution, and filtered using 0.45 µm PVDF membranes (Durapore®, Merck Millipore).…”

Crosslinked Resin‐Supported Bifunctional Organocatalyst for Conversion of CO2 into Cyclic Carbonates

“…Being different from the traditional process that using of 1,2‐diols and the highly toxic carbonylation reagent (phosgene and its derivatives), the cyclization of CO 2 and epoxide into cyclic carbonate avoid producing condensation product, which is well in line with the atomic economy. From an application viewpoint, cyclic carbonates, such as propylene carbonate (PC) and ethylene carbonate (EC), are vastly used as polar aprotic solvents, electrolytes in the battery, and vital intermediates in the manufacture of fine chemicals . Given the thermodynamic stability and chemical inertness of CO 2 , the development of an active catalyst to circumvent high temperature and pressure is highly required to facilitate this coupling process, thus making the coupling process greener .…”