Abstract
The use of renewable feedstock is one of the twelve key principles of sustainable chemistry. Unfortunately, bio-based compounds often suffer from high production cost and low performance. To fully tap the potential of natural compounds it is important to utilize their functionalities that could make them superior compared to fossil-based resources. Here we show the conversion of (+)-3-carene, a by-product of the cellulose industry into ε-lactams from which polyamides. The lactams are selectively prepared in two diastereomeric configurations, leading to semi-crystalline or amorphous, transparent polymers that can compete with the thermal properties of commercial high-performance polyamides. Copolyamides with caprolactam and laurolactam exhibit an increased glass transition and amorphicity compared to the homopolyamides, potentially broadening the scope of standard polyamides. A four-step one-vessel monomer synthesis, applying chemo-enzymatic catalysis for the initial oxidation step, is established. The great potential of the polyamides is outlined.
Highlights
The use of renewable feedstock is one of the twelve key principles of sustainable chemistry
A literature protocol using high amounts of ZnBr2 in EtOAc resulted in 59% yield, consisting of a mixture of the diastereoisomeric ketones 3-3S and 3-3R, which can be identified by Gas chromatography mass spectrometry (GCMS), (Supplementary Methods, Supplementary Fig. 1, Supplementary Table 1)[50]
As a mixture of stereoisomers would eventually result in an atactic polyamide, we were interested in a stereoselective catalysis which would enable the synthesis of the pure isomers—but complex[51,52] and costly[53,54,55,56] catalysts should be avoided
Summary
The use of renewable feedstock is one of the twelve key principles of sustainable chemistry. Sustainable monomer sources can be serious alternatives to fossil oil, as demonstrated by the commercially available bio-based polyamides PA1010, PA11, or PA410 These examples are linear, non-chiral condensation polyamides composed of diacids or amino acids derived from castor oil. In this context, we consider especially monoterpenes from renewable feedstocks to be a promising source for biogenic polymers. We consider especially monoterpenes from renewable feedstocks to be a promising source for biogenic polymers Monoterpenes such as limonene, camphor, menthone, α- and βpinene, or 3-carene provide valuable carbon structures such as aliphatic rings and can be isolated from waste streams of biomassutilizing processes in high volumes[20]. Winnacker et al.[39,40] reproduced, investigated, and optimized the synthesis and polymerization and tested the application of the new polyamide in cell growth control
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