Mid Sweden University

Lightweight materials with high strength are desirable for advanced applications in transportation, sports equipment, construction, automotive, and aerospace. Aspen is fast growing, has low flammability, and is renewable and readily available. In this study, we present a continuous, high-yielding, efficient, scalable, and sustainable approach for the fabrication of strong materials from aspen by synergistic selective chemical modification and continuous hot pressing. FTIR analysis revealed changes in the chemical composition of the wood polymers, including the introduction of anionic groups, while SEM images showed morphological and structural transformations such as smoother surfaces and a more compact wood structure. The proposed strategy achieved up to 258 MPa (530% increase) in tensile strength by combining enhanced ion-bonding and hydrogen-bonding with the alignment of cellulose nanofibrils and the solidification of softened, depolymerized lignin through cross-linking reactions. This work demonstrates the continuous large-scale production of lightweight, strong structural materials under energy-efficient and mild modification conditions, suitable for the green fabrication of next-generation advanced materials from wood. 

Highly selective conjugate additions of Grignard reagents to cyclic and linear enones catalyzed by recyclable heterogeneous polysaccharide/nanocopper catalysts are disclosed. The method also allows the synthesis of ketones with an all-carbon quaternary center. When integrated with catalytic asymmetric tandem reactions using enals and β-ketoesters, it yields chiral β,δ-disubstituted ketones with high stereoselectivity. 

Herein, we present a highly efficient allylic substitution of carbonates with Grignard reagents using a reusable cellulose-supported nanocopper catalyst. This approach highlights the first instance of heterogeneous catalysis for the cross-coupling of allylic alcohol substrates with Grignard reagents. The method features high yields, excellent regioselectivity, and complete chirality transfer.

A concept for developing stable, water-based colloids for simple, effective, green, and organocatalytic hydrophobization of heterogeneous polysaccharide-based materials (e.g., cellulose, wood, and paper) in water is disclosed. The addition of a surfactant, an organocatalyst, and a hydrophobic agent (e.g., alkyl trialkoxysilane) to water results in organocatalytic polymerization and the formation of a water-based suspension, which, upon homogenization, forms a stable colloid. The mechanism for the generation of this organocatalytic aqueous formulation (OAF) is elucidated by microscopy and spectroscopy. It is initiated by organocatalytic alkyl alkoxysilane polymerization within the nanomicelles formed by the surfactant in water through an "on-water" Type IIa mechanism. Next, these micelles expand to a microsize upon further polymerization, eventually leading to aggregation and the formation of a suspension through an "on-water" Type III mechanism. Homogenizing this suspension yields a stable colloid with water as the medium. The OAFs were then applied to various cellulosic substrates (e.g., cellulose paper, paper sheets, cotton, and wood) by spraying, roll-coating, or dipping. Organocatalytic colloidal particle modification of a wide range of cellulosic substrates (e.g. paper, cotton, and wood) in water through an "on-water" mechanism, which we here classify as Type IV, results in hydrophobic (contact angles of >145 degrees) or superhydrophobic (contact angles of >150 degrees) cellulosic surfaces. Thus, the OAFs can be utilized for modifying a wide range of industrially relevant cellulose-based materials under eco-friendly conditions. The dual role of the organocatalyst in mediating colloidal particle formation and green hydrophobic modification of heterogeneous polysaccharides exemplifies a novel approach for harnessing the catalytic potential of small molecules for organic reactions in water.

In this Chapter, we review some of the latest developments in aminocatalytic direct alpha-heteroatom functionalization, alpha-alkylation and allylation of carbonyl compounds. Tremendous advances have been made and it is an important field with remarkable selectivity in the construction and design of chiral molecules with the focus of the betterment of human health. 

There is a growing demand for the utilization of sustainable materials, such as cellulose-based alternatives, over fossil-based materials. However, the inherent drawbacks of cellulosic materials, such as extremely low wet strength and resistance to moisture, need significant improvements. Moreover, several of the commercially available wet-strength chemicals and hydrophobic agents for cellulosic material treatment are toxic or fossil-based (e.g., epichlorohydrin and fluorocarbons). Herein, we present an eco-friendly, high-yield, industrially relevant, and scalable method inspired by birch bark for fabricating hydrophobic and strong cellulosic materials. This was accomplished by combining simple surface modification of cellulosic fibers in water using colloidal particles of betulin, an abundant triterpene extracted from birch bark, with sustainable chemical engineering (e.g., lignin modification and hot-pressing). This led to a transformative process that not only altered the morphology of the cellulosic materials into a more dense and compact structure but also made them hydrophobic (contact angles of up to >130°) with the betulin particles undergoing polymorphic transformations from prismatic crystals (betulin III) to orthorhombic whiskers (betulin I). Significant synergistic effects are observed, resulting in a remarkable increase in wet strength (>1400%) of the produced hydrophobic cellulosic materials.

A direct catalytic stereoselective synthesis of C4’ functionalized furanoside and nucleoside derivatives with a tetrasubstituted stereocenter is disclosed. The amine-catalyzed stereoselective α-aminomethylation reactions on furanoside-derived aldehyde derivatives gave the corresponding C4’ functionalized D- or L-ribose derivatives in good to excellent yields (67−94%) with up to >20:1 dr. 

Three boron dipyrromethane molecules (BODIPYs) were synthesized in this study with different quantities of fluorine in the meso position. The samples were characterized by NMR spectroscopy, absorption, mass spectrometry, and cyclic voltammetry, which was utilized to electrochemically measure the energy gaps between the HOMO (highest-energy occupied molecular orbital) and LUMO (lowest-energy unoccupied molecular orbital). The MTT and SRB assays were used to assess the viability of these dyes in breast cancer cells (MCF-7 and HCC-1806) and African green monkey kidney cells (Vero). The newly synthesized BODIPY tris(perfluorophenoxy)phenyl (1) compound has exhibited remarkable stability and lacks photocytotoxicity in this investigation, thus rendering it a promising candidate for application in bioimaging. At defined concentrations, the BODIPYs bearing perfluorophenyl (2) and hydroxyphenyl (3) moieties have been identified as prospective candidates for photosensitization in photodynamic therapy for breast cancer. Their notable phototoxic properties upon irradiation and the absence of significant metabolic activity reduction in normal VERO cells after 24 h of exposure suggest their potential efficacy in this therapeutic approach.

Herein, we describe a solvent-free bioinspired approach for the polymerization of ethylene brassylate. Artificial plant cell walls (APCWs) with an integrated enzyme were fabricated by self-assembly, using microcrystalline cellulose as the main structural component. The resulting APCW catalysts were tested in bulk reactions and reactive extrusion, leading to high monomer conversion and a molar mass of around 4 kDa. In addition, we discovered that APCW catalyzes the formation of large ethylene brassylate macrocycles. The enzymatic stability and efficiency of the APCW were investigated by recycling the catalyst both in bulk and reactive extrusion. The obtained poly(ethylene brassylate) was applied as a biobased and biodegradable hydrophobic paper coating.