Sustainable mechanosynthesis of diamide tetraols monomers and their enzymatic polymerization

Abstract

A novel method for synthesizing biobased diamide tetraol derivatives through mechanochemical processes is presented in this study. The key component used in the synthesis is (S)-γ-hydroxymethyl-γ-butyrolactone (2H-HBO), a cellulose-based lactone derived from levoglucosenone, combined with various linear diamines. The use of planetary ball milling in the presence of a small excess of diamine was found to be crucial for achieving complete conversion of 2H-HBO and the selective formation of diamide tetraol derivatives. The optimized parameters established for the reaction of 2H-HBO using diaminohexane were applied to biobased, non-toxic, and biodegradable diamines such as spermidine, spermine, and 4,9-dioxa-dodecanediamine. This resulted in high conversions and good yields of diamide tetraol derivatives. The scalability of the process was demonstrated by transposing the reaction from 100 mg to 2 g, with improved conversions obtained at a larger scale. The greenness of the procedure was assessed using the E-factor and EcoScale, showing low waste generation and acceptable to excellent reaction conditions. In addition, enzymatic polymerization of diamide tetraol derivatives using CAL-B (Candida antarctica lipase B) as a biocatalyst was explored. Successful polymerization of monomers obtained from hexamethylene diamine and 4,9-dioxa-dodecandiamine was achieved, providing insights into the effect of enzyme loading and monomer ratios on the molecular weight of the resulting polymers. Despite challenges with certain monomers containing amine groups, this work offers a promising approach for producing multifunctional biobased polymers.