The efficient valorization of lignin could dictate the success of the 2nd generation biorefinery. Lignin, accounting for on average a third of the lignocellulosic biomass, is the most promising ...candidate for sustainable production of value‐added phenolics. However, the structural alteration induced during lignin isolation is often depleting its potential for value‐added chemicals. Recently, catalytic reductive depolymerization of lignin has appeared to be a promising and effective method for its valorization to obtain phenolic monomers. The present study systematically summarizes the far‐reaching and state‐of‐the‐art lignin valorization strategies during different stages, including conventional catalytic depolymerization of technical lignin, emerging reductive catalytic fractionation of protolignin, stabilization strategies to inhibit the undesired condensation reactions, and further catalytic upgrading of lignin‐derived monomers. Finally, the potential challenges for the future researches on the efficient valorization of lignin and possible solutions are proposed.
“Lignin‐first” biorefinery: Catalytic valorization of lignin provides a promising and attractive strategy for producing value‐added phenolic monomers. The recent advances in catalytic depolymerization of technical lignin and reductive catalytic fractionation of protolignin are comprehensively summarized. The mechanism of condensation reactions and possible solutions are also discussed.
The Front Cover shows how a path to biobased monomers has been formed by combining furfural, derived from biomass waste, and aldehydes. A combined experimental–theoretical investigation made it ...possible to predict the molecular diversity and complexity this path may support. More information can be found in the Research Article by F. Jérôme and co‐workers.
Achieving well‐defined polymers with ultrahigh molecular weight (UHMW) is an enduring pursuit in the field of reversible deactivation radical polymerization. Synthetic protocols have been ...successfully developed to achieve UHMWs with low dispersities exclusively from conjugated monomers while no polymerization of unconjugated monomers has provided the same level of control. Herein, an oxygen‐tolerant photoenzymatic RAFT (reversible addition‐fragmentation chain transfer) polymerization was exploited to tackle this challenge for unconjugated monomers at 10 °C, enabling facile synthesis of well‐defined, linear and star polymers with near‐quantitative conversions, unprecedented UHMWs and low dispersities. The exquisite level of control over composition, MW and architecture, coupled with operational ease, mild conditions and environmental friendliness, broadens the monomer scope to include unconjugated monomers, and to achieve previously inaccessible low‐dispersity UHMWs.
Well‐defined polymers with ultrahigh molecular weight were achieved with an oxygen‐tolerant photoenzymatic RAFT polymerization performed at 10 °C. The facile synthesis, in aqueous solution and without prior deoxygenation, produces well‐defined linear and star polymers with near‐quantitative conversions, ultrahigh molecular weight, and low dispersities.
Methods to synthesize crystalline covalent triazine frameworks (CTFs) are limited and little attention has been paid to development of hydrophilic CTFs and photocatalytic overall water splitting. A ...route to synthesize crystalline and hydrophilic CTF‐HUST‐A1 with a benzylamine‐functionalized monomer is presented. The base reagent used plays an important role in the enhancement of crystallinity and hydrophilicity. CTF‐HUST‐A1 exhibits good crystallinity, excellent hydrophilicity, and excellent photocatalytic activity in sacrificial photocatalytic hydrogen evolution (hydrogen evolution rate up to 9200 μmol g−1 h−1). Photocatalytic overall water splitting is achieved by depositing dual co‐catalysts in CTF‐HUST‐A1, with H2 evolution and O2 evolution rates of 25.4 μmol g−1 h−1 and 12.9 μmol g−1 h−1 in pure water without using sacrificial agent.
All about the base: A benzylamine‐functionalized monomer is used to synthesize crystalline and hydrophilic CTF‐HUST‐A1. The base reagent used in the reaction plays an important role in the enhancement of the crystallinity and hydrophilicity. The resulting CTF‐HUST‐A1 shows excellent activity in photocatalytic hydrogen evolution.
Transition‐metal‐catalyzed copolymerization of olefins with polar monomers represents a challenge because of the large variety of substrate‐induced side reactions. However, this approach also holds ...the potential for the direct synthesis of polar functionalized polyolefins with unique properties. After decades of research, only a few catalyst systems have been found to be suitable for this reaction. Some major advances in catalyst development have been made in the past five years. This Minireview summarizes some of the recent progress in the extensively studied Brookhart and Drent catalyst systems, as well as emerging alternative palladium and nickel catalysts.
The polar challenge: Transition‐metal‐catalyzed copolymerization of olefins with polar monomers represents a challenge in the field of olefin polymerization. This Minireview summarizes some recent progress with the extensively studied Brookhart and Drent catalysts, as well as some emerging alternative palladium and nickel catalysts.
This opinion article describes recent approaches to use the “biorefinery” concept to lower the carbon footprint of typical mass polymers, by replacing parts of the fossil monomers with similar or ...even the same monomer made from regrowing dendritic biomass. Herein, the new and green catalytic synthetic routes are for lactic acid (LA), isosorbide (IS), 2,5‐furandicarboxylic acid (FDCA), and p‐xylene (pXL). Furthermore, the synthesis of two unconventional lignocellulosic biomass derivable monomers, i.e., α‐methylene‐γ‐valerolactone (MeGVL) and levoglucosenol (LG), are presented. All those have the potential to enter in a cost‐effective way, also the mass market and thereby recover lost areas for polymer materials. The differences of catalytic unit operations of the biorefinery are also discussed and the challenges that must be addressed along the synthesis path of each monomers.
The search for less invasive and even degradable polymers can also be addressed by the availability of economic, partly new monomers based on biomass instead of fossil resources. Some elemental processes of biorefinery are reviewed based on lignocellulosic biomass and the monomers they create.
With the growing interest in bioplastics, there is an urgent need to develop rapid analysis methods linked to production technology development. This study focused on the production of a commercially ...non-available homopolymer, poly(3-hydroxyvalerate) (P(3HV)), and a commercially available copolymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-co-3HV)), through fermentation using two different bacterial strains. The bacteria Chromobacterium violaceum and Bacillus sp. CYR1 were used to produce P(3HV) and P(3HB-co-3HV), respectively. The bacterium Bacillus sp. CYR1 produced 415 mg/L of P(3HB-co-3HV) when incubated with acetic acid and valeric acid as the carbon sources, whereas the bacterium C. violaceum produced 0.198 g of P(3HV)/g dry biomass when incubated with sodium valerate as the carbon source. Additionally, we developed a fast, simple, and inexpensive method to quantify P(3HV) and P(3HB-co-3HV) using high-performance liquid chromatography (HPLC). As the alkaline decomposition of P(3HB-co-3HV) releases 2-butenoic acid (2BE) and 2-pentenoic acid (2PE), we were able to determine the concentration using HPLC. Moreover, calibration curves were prepared using standard 2BE and 2PE, along with sample 2BE and 2PE produced by the alkaline decomposition of poly(3-hydroxybutyrate) and P(3HV), respectively. Finally, the HPLC results obtained by our new method were compared using gas chromatography (GC) analysis.
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Aliphatic/alicyclic (Al)-containing polyimides (PIs), including fully-Al-PIs and partially-Al-PIs, are widely employed in electric, electronics, optical materials, and other advanced ...material fields. Examples include high speed multiplayer printed wiring boards, alignment films for liquid-crystal displays, fuel cells, batteries, gas separation membranes, pervaporation membranes, biomedical applications, and composites/hybrid materials. In the past decades, research has focused on the synthesis and molecular design of fully-Al-PIs and partially-Al-PIs. However, the effects of aliphatic/alicyclic segments on the performance of fully-Al-PIs and partially-Al-PIs and their potential applications are not clear. Therefore, an overall clarification of aliphatic/alicyclic-containing monomers, the effects of aliphatic/alicyclic segments on PI performance, as well as recent applications for advanced technology are important topics for further study. This review systematically summarizes the available aliphatic/alicyclic monomers and clarifies the influence of aliphatic/alicyclic-containing segments in chain backbones on the morphology and properties of the resulting PIs. Further, the use of PIs in applications for advanced materials is discussed, along with the outlook for the future of aliphatic/alicyclic-containing polyimides and their advanced applications.
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