Efficient Conversion of Cellulose to Thermoplastics by Mechanochemical Esterification

Abstract

Despite the melting processibility of cellulose is of great importance to convert this abundant biomass to various products, the efficient and sustainable preparation of a thermoplastic cellulose material remains a challenge. Herein, we report a novel one-step ball-milling mechanochemistry method for efficiently converting cellulose to melt-processable cellulose stearates (SCEs) without sacrificing excess reagents. By adjusting the reaction conditions, a series of SCEs with degrees of substitution (DS) ranging from 1.30 to 2.37 are synthesized. Besides, the relationship between DS and the thermoplasticity of SCEs is well investigated. The obtained SCEs with DS beyond 1.62 show favorable thermoplasticity, which can be processed into homogeneous films with a maximum tensile strength of 12.4 MPa and an elastic modulus of 353.6 MPa by a conventional hot-pressing technique (160 °C, 10 MPa). Moreover, this method is universally used for achieving various thermoplastic fatty acid cellulose esters with different numbers of carbons (10−18) in side chains. Due to its high efficiency and sustainability, this approach holds great potential for the large-scale fabrication of thermoplastic cellulosebased materials.

Insight into the Feasibility of Fatty Acyl Chlorides with 10–18 Carbons for the Ball-Milling Synthesis of Thermoplastic Cellulose Esters

“…In our previous research, thermoplastic FACE were rapidly synthesized by an efficient ball-milling esterification method. 40 However, the effect of different chain lengths of fatty acyl chlorides on the structures and properties of the resulting FACE remains unknown. To elucidate this effect, a series of FACE were synthesized by individually ball-milling intact MCC and various fatty acyl chlorides containing 10−18 carbons (Figure 1a,b).…”

“…In our previous research, thermoplastic FACE were rapidly synthesized by an efficient ball-milling esterification method . However, the effect of different chain lengths of fatty acyl chlorides on the structures and properties of the resulting FACE remains unknown.…”

“…Ball-Milling Synthesis of FACE. Based on our previously reported ball-milling esterification strategy, 40 a series of FACE, including cellulose decanoate (CDE), cellulose laurate (CLE), cellulose myristate (CME), cellulose palmitate (CPE), and cellulose stearate (CSE), were prepared by ball-milling MCC with DeyCl, LayCl, MyyCl, PayCl, and StyCl, respectively. Taking the synthesis of CDE as a representative, 0.162 g of MCC, stoichiometric DeyCl, and 1.0 mL of pyridine were once added into a 100 mL stainless-steel mill pot.…”

“…Recently, our group reported a "onestep" ball-milling esterification method for efficiently preparing thermoplastic fatty acid cellulose esters (FACE), which has advantages over traditional strategies in terms of reducing reagent consumption and improving efficiency. 40 However, it is still elusive to the effect of the fatty acyl chlorides with various chain lengths on the structures and thermoplasticity of the resulting FACE.…”

“…However, conventional strategies for synthesizing thermoplastic cellulose esters nearly face challenges, such as substantial solvent (or reagent) consumption with environmental pressure and complex processing steps with low fabrication efficiency. Recently, our group reported a “one-step” ball-milling esterification method for efficiently preparing thermoplastic fatty acid cellulose esters (FACE), which has advantages over traditional strategies in terms of reducing reagent consumption and improving efficiency . However, it is still elusive to the effect of the fatty acyl chlorides with various chain lengths on the structures and thermoplasticity of the resulting FACE.…”