Lignin produced in the kraft pulping process is insoluble in water at neutral pH, which limits its application in industry. In this paper, kraft lignin (KL) was copolymerized with acrylic acid (AA) ...in an aqueous solution to produce a water soluble lignin-based copolymer. The copolymerization was carried out using K sub(2)S sub(2)O sub(8)-Na sub(2)S sub(2)O sub(3) as the initiator under alkaline aqueous conditions, and the influence of the reaction parameters, i.e.initiator dosage, reaction time and temperature, mole ratio of acrylic acid to lignin and reaction concentration, on resultant lignin copolymers were investigated. The mechanism of copolymerization of kraft lignin with acrylic acid was also discussed in this work. The resultant lignin copolymer was characterized by Fourier Transform Infrared (FTIR) spectrophotometry and Nuclear Magnetic Resonance (NMR). The successful copolymerization of AA and KL was confirmed by the new absorption peak of carboxyl anions in the FTIR spectrum and new peaks in the super(1)H-NMR spectrum. At optimal conditions, the charge density and molecular weight of lignin copolymer reached 1.86 meq g super(-1) and 46 421 g mol super(-1), respectively, and the solubility of lignin after reaction was increased from 1.80 g L super(-1) to 100 g L super(-1) at neutral pH.
The straightforward synthesis and detailed characterization of nine substituted triarylformazanate boron difluoride complexes is reported. The effect of electron-donating (p-anisole) and ...electron-withdrawing (p-benzonitrile) substituents on optical and electrochemical properties, relative to phenyl substituents, was studied at two different positions within the formazanate ligand framework. Each of the BF2 complexes was characterized by 1H, 13C, 11B, and 19F NMR spectroscopy, cyclic voltammetry, infrared spectroscopy, UV–vis absorption and emission spectroscopy, mass spectrometry, and elemental analysis. Select examples were studied by X-ray crystallography, revealing highly delocalized structures in the solid state. The complexes were reversibly reduced in two steps electrochemically to their radical anion and dianion forms. The complexes also exhibited substituent-dependent absorption and emission properties, accompanied by significant Stokes shifts, with the aryl substituents at the 1,5-positions of the formazanate backbone having a greater influence on these properties than aryl substituents at the 3-position. Breaking the symmetry in three different complexes resulted in a modest increase in emission intensity relative to that of symmetrically substituted derivatives.
The straightforward synthesis of a series of 3‐cyanoformazanate boron difluoride dyes is reported. Phenyl, 4‐methoxyphenyl and 4‐cyanophenyl N‐substituted derivatives were isolated and characterized ...by single‐crystal X‐ray crystallography, cyclic voltammetry, and UV/Vis spectroscopy. The compounds were demonstrated to possess tunable, substituent‐dependent absorption, emission, and electrochemical properties, which were rationalized through electronic structure calculations.
Simple but bright: A novel class of boron difluoride dyes based on 3‐cyanoformazanate ligands is reported. The dyes were synthesized by straightforward synthetic methods and shown to possess readily tunable and substituent‐dependent absorption, emission, and electrochemical properties. The trends observed in experimental results were confirmed and rationalized by using electronic structure calculations.
Mushroom bodies (MB) of adult
have a core of thousands of Kenyon neurons; axons of the early-born g class form a medial lobe and those from later-born α'β' and αβ classes form both medial and ...vertical lobes. The larva, however, hatches with only γ neurons and forms a vertical lobe 'facsimile' using larval-specific axon branches from its γ neurons. MB input (MBINs) and output (MBONs) neurons divide the Kenyon neuron lobes into discrete computational compartments. The larva has 10 such compartments while the adult has 16. We determined the fates of 28 of the 32 MBONs and MBINs that define the 10 larval compartments. Seven compartments are subsequently incorporated into the adult MB; four of their MBINs die, while 12 MBINs/MBONs remodel to function in adult compartments. The remaining three compartments are larval specific. At metamorphosis their MBIN/MBONs trans-differentiate, leaving the MB for other adult brain circuits. The adult vertical lobes are made
using MBONs/MBINs recruited from pools of adult-specific neurons. The combination of cell death, compartment shifting, trans-differentiation, and recruitment of new neurons result in no larval MBIN-MBON connections being maintained through metamorphosis. At this simple level, then, we find no anatomical substrate for a memory trace persisting from larva to adult. The adult phenotype of the trans-differentiating neurons represents their evolutionarily ancestral phenotype while their larval phenotype is a derived adaptation for the larval stage. These cells arise primarily within lineages that also produce permanent MBINs and MBONs, suggesting that larval specifying factors may allow information related to birth-order or sibling identity to be interpreted in a modified manner in the larva to allow these neurons to acquire larval phenotypic modifications. The loss of such factors at metamorphosis then allows these neurons to revert to their ancestral functions in the adult.
There is a growing need to utilize lignin (i.e., wasted material) from the pulping industry in the production of value-added products and to develop cost-effective and environmentally friendly ...processes for removing dyes from wastewater effluents. In this context, lignin can be modified to gain anionic charges, which can successfully remove cationic dyes from wastewater. In this study, lignin was extracted from thermomechanical pulp (softwood) via periodate treatment, and then the extracted lignin was oxidized using 30 wt % nitric acid concentration at 80 °C for 1.5 h, which resulted in oxidized lignin with the charge density and solubility of 3.02 mequiv/g and 97% (at a 1 wt % lignin concentration), respectively. The oxidized lignin was used for removing ethyl violet and basic blue cationic dyes from simulated wastewater effluents. It was observed that the dye removals were in the ranges of 70–80 wt % for ethyl violet and of 80–95 wt % for basic blue, while the COD removals were in the ranges of 60–70% for ethyl violet and 70–85% for basic blue when the concentrations of dyes varied between 50 and 400 mg/L. The dye removal was pH dependent, and the removal of basic blue decreased from 84 wt % (in the absence of salt) to 77% in the presence of 3 g/L NaCl, whereas salt had a marginal effect on the removal of ethyl violet from the solution.
A protection-deprotection strategy for strained alkynes used for bioorthogonal chemistry is reported. A strained alkyne can be protected with dicobalt-octacarbonyl and we demonstrate for the first ...time that a strained alkyne can be re-formed and isolated under mild reaction conditions for further bioorthogonal reactivity. The protection-deprotection strategy herein reported will expand the versatility of strained alkynes for the preparation of substrates in chemical biology and materials applications.
One of the most common strategies for the production of molecular materials with optical properties in the far-red/near-IR regions of the electromagnetic spectrum is their incorporation into dimeric ...architectures. In this paper, we describe the synthesis and characterization ( 1 H, 11 B, 13 C and 19 F NMR spectroscopy, IR and UV-vis absorption and emission spectroscopy, mass spectrometry and X-ray crystallography) of the first examples of boron difluoride (BF 2 ) formazanate dimers. Specifically, the properties of meta - and para -substituted benzene-bridged dimers p-10 and m-10 were compared to closely related boron difluoride triphenyl formazanate complex 11 in order to assess the effect of electronic conjugation and cross conjugation on their light absorption/emission and electrochemical properties. While the properties of cross-conjugated dimer m-10 did not differ significantly from those of monomer 11 , conjugated dimer p-10 exhibited red-shifted absorption and emission maxima and was easier to reduce electrochemically to its bis radical anion and bis dianion form compared to monomer 11 . Both dimers are weakly emissive in the far-red/near-IR and exhibited large Stokes shifts (>110 nm, 3318 cm −1 ). Unlike a closely related para -substituted benzene-bridged boron dipyrromethene (BODIPY) dimer, the emission quantum yields measured for the BF 2 formazanate dimers exceeded those observed for monomeric analogues.
Within the past decade photochromic materials, specifically dithienylethenes (DTEs), have received increased interest because of their ability to function as potential photoswitchable molecular ...devices and optical memory storage systems. Current research in this area has focused on incorporating organic architectures to functionalize the DTE framework and alter the resulting photophysical properties; however, their syntheses are often not trivial. In this context, we have designed a simple and versatile diimine (2) containing adjacent 2,5‐dimethyl(thienyl) rings in the backbone. This redox active diimine (2) acts as a precursor to a novel photochromic ligand and has been used to coordinate to both boron and phosphorus elements, along with the synthesis of a phosphorane‐side‐chain functionalized polymer without further functionalization to the parent DTE framework. A study of the resulting photochromic properties of these compounds revealed that 1) the UV‐visible absorption spectra of the closed‐ring isomer were dependent of the element present in the N,N′‐chelating pocket and 2) incorporating the dithienylethene into a side‐functionalized phosphorane polymer greatly increased the closed‐/open‐ring reversibility and decreased the formation of by‐products.
Switching it up! A versatile redox‐active diazabutadiene (DAB) ligand containing photochromic dithienylethene rings in the backbone has been synthesized. The coordination of both BIII and PIII has been demonstrated, along with the facile functionalization of the PIII heterocycle with a polymerizable group and the synthesis of a photochromic side‐chainfunctionalized polymer (see figure).
The search for a renewable substitute to petroleum‐based products has fueled increasing research on lignin, an under‐utilized product from pulping processes. In this work, lignin was copolymerized ...with acrylamide (AM) and diallyldimethylammonium chloride (DADMAC) under acidic conditions with Na2S2O8 as an initiator, generating a cationic water‐soluble lignin‐g‐P(AM)‐g‐P(DADMAC) copolymer. The optimal reaction conditions, using a 5×4 factorial design experiment, were determined to be an AM/DADMAC/lignin molar ratio of 5.5:2.4:1, 90 °C, 0.26 mol L−1 of lignin, and pH 2. Under the optimal reaction conditions, the resulting lignin‐g‐P(AM)‐g‐P(DADMAC) copolymer was 83 % soluble in an aqueous solution (at 10 g L−1) and at neutral pH. The copolymer had a charge density of 1.27 meq g−1, molecular weight of (1.33±0.08) ×106, an AM grafting ratio of 112 wt %, and a DADMAC grafting ratio of 20 wt %. In addition, the activation energy for producing this copolymer as well as the thermal and rheological properties of the copolymer were determined. The flocculation performance of lignin‐g‐P(AM)‐g‐P(DADMAC) copolymer was evaluated in a kaolin suspension, which showed that the lignin copolymer had a comparable flocculation efficiency with the synthetic analogue of P(AM)‐g‐P(DADMAC) at pH 6.
Fueling research: Copolymerization of kraft lignin, acrylamide, and a cationic monomer is comprehensively studied in an acidic aqueous system. The properties of the product are fundamentally assessed, and the product shows promising results as a flocculant.
There has been a strong push to develop new thiophene-based monomers to tailor the electrical and optical properties of the resulting polymers. However, the synthesis of these elaborated thienyl ...compounds is difficult to realize. Here, we report the successful click coupling of thienyl azides and para-substituted aryl alkynes to synthesize eight thiophene-based luminophores intended for electrochemical and electrochemiluminescence (ECL) study. These thiophenes could be separated into two series: monothienyl and bithienyl analogues and further categorized based on the nature of the ligand attachment to their phenyl rings (electron-donating or -withdrawing characteristics: NMe2, OMe, H, or F) on the other side of the triazole bridge. The electrochemical experiments indicated these compounds lacked stability when they were oxidized or reduced, with the exception of those with a dimethylamine ligand attached (quasireversible oxidations). Cyclic and differential pulse voltammetries revealed the redox potentials of these compounds were affected by the extent of the conjugation and the nature of the ligands, while the electrochemical gaps correlated well with the energy differences between the excited and ground state species. ECL in the annihilation route confirmed the weak light-emitting nature of these thiophenes; however, great improvement was made with the use of a coreactant species (benzoyl peroxide or ammonium persulfate). ECL spectroscopy revealed that the excimer or polymeric excited states were more favorable in formation than their monomeric excited states, which was tunable based on the applied potentials. Structural insight into ECL will guide us to discover optimized thiophene-based luminophores.
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