Effects of Alcell Lignin Methylolation and Lignin Adding Stage on Lignin-Based Phenolic Adhesives

To investigate the effects of lignin methylolation and lignin adding stage on the resulted lignin-based phenolic adhesives, Alcell lignin activated with NaOH (AL) or methylolation (ML) was integrated into the phenolic adhesives system by replacing phenol at various adhesive synthesis stages or directly co-polymerizing with phenolic adhesives. Lignin integration into phenolic adhesives greatly increased the viscosity of the resultant adhesives, regardless of lignin methylolation or adding stage. ML introduction at the second stage of adhesive synthesis led to much bigger viscosity than ML or AL introduction into phenolic adhesives at any other stages. Lignin methylolation and lignin adding stage did not affect the thermal stability of lignin based phenolic adhesives, even though lignin-based adhesives were less thermally stable than NPF. Typical three-stage degradation characteristics were also observed on all the lignin-based phenolic adhesives. Three-ply plywoods can be successfully laminated with lignin based adhesives, and it was interesting that after 3 h of cooking in boiling water, the plywoods specimens bonded with lignin-based phenolic adhesives displayed higher bonding strength than the corresponding dry strength obtained after direct conditioning at 20 °C and 65% RH. Compared with NPF, lignin introduction significantly reduced the bonding strength of lignin based phenolic adhesives when applied for plywood lamination. However, no significant variation of bonding strength was detected among the lignin based phenolic adhesives, regardless of lignin methylolation or adding stages.     

Studies on the copolymerisation of N-isopropyl-acrylamide with glycidyl methacrylate

The paper describes the homopolymerisation and copolymerisation of N-isopropyl acrylamide (NIPAM) with glycidyl methacrylate (GMA) in solution at 60°C using azobisisobutyronitrile (AIBN) as an initiator and dioxan as solvent. Copolymers were synthesized by varying the mol fraction of GMA in the initial feed from 0.025-0.125. All the polymerization reactions were terminated at low % conversion (10-15%) and the copolymer composition was determined by measuring the epoxy content. Percent epoxy content was determined by titration method using pyridine-HCl mixture. The reactivity ratios determined using Fineman-Ross method were found to be 0.94±0.05 (r₁, NIPAM) and 1.05±0.08 (r₂, GMA). All the polymers have high molecular weights with wide molecular weight distribution as determined by gel permeation chromatography (GPC) i.e. M_n in the range of 3.7 x 10⁴ - 7.8 x 10⁴ and M_w in the range of 1.2 x 10⁵ - 4.1 x 10⁵ with a polydispersity index in the range of 2.3-5.3. Lower critical solution temperature (LCST) of NIPAM homopolymer and copolymers was determined by recording DSC scans of polymers in aqueous solution. Incorporation of GMA in the poly(NIPAM) backbone resulted in a decrease in the LCST.     

Adsorption of methyl isocyanate on M4 (M=Fe,Ni, and Cu) cluster-decorated graphene and vacancy graphene: a DFT-D2 study

Structural Chemistry - Adsorption of a toxic gas, methyl isocyanate (MIC), has been studied on different metal (Fe, Ni, and Cu) cluster-decorated graphene and vacancy graphene. The binding of M4...     

Modular Adder Designs Using Optimal Reversible and Fault Tolerant Gates in Field-Coupled QCA Nanocomputing

The challenges which the CMOS technology is facing toward the end of the technology roadmap calls for an investigation of various logical and technological solutions to CMOS at the nano scale. Two such paradigms which are considered in this paper are the reversible logic and the quantum-dot cellular automata (QCA) nanotechnology. Firstly, a new 3 × 3 reversible and universal gate, RG-QCA, is proposed and implemented in QCA technology using conventional 3-input majority voter based logic. Further the gate is optimized by using explicit interaction of cells and this optimized gate is then used to design an optimized modular full adder in QCA. Another configuration of RG-QCA gate, CRG-QCA, is then proposed which is a 4 × 4 gate and includes the fault tolerant characteristics and parity preserving nature. The proposed CRG-QCA gate is then tested to design a fault tolerant full adder circuit. Extensive comparisons of gate and adder circuits are drawn with the existing literature and it is envisaged that our proposed designs perform better and are cost efficient in QCA technology.     

Lysozyme-imprinted polymer synthesized using UV free-radical polymerization

Molecular imprinting is a method to fabricate a polymeric material (molecularly imprinted polymer or MIP) capable of selectively recognizing template molecules. Molecular imprinting of small molecules has been studied widely. Less common, however, is the imprinting of biological macromolecules, including proteins, among which lysozyme is an important molecule in the food, pharmaceutical, and diagnostic sciences. In this study, lysozyme MIP was fabricated in two steps. First, lysozyme, PEG600DMA, and methacrylic acid were used as the template molecule, cross-linking monomer, and the functional monomer, respectively, in a UV free-radical polymerization process to synthesize a polymeric gel. Second, lysozyme was removed by enzymatic digestion. Non-imprinted polymer (NIP) was synthesized without lysozyme addition. To evaluate the preferential binding capability of MIP, lysozyme, RNase A, or a 50:50 mixture of lysozyme and RNase A was added to MIP and NIP and then released by digestion. It was found that when more lysozyme was added to the reaction mixture, the quantity of protein released from the polymer increased, reflecting more potential binding sites. Tests of MIP with a competitive binding mixture of lysozyme and RNase A showed the MIP preferentially bound a greater amount of lysozyme, up to 20 times more than RNase A. NIP bound only small amounts of both proteins and did not show a preference for binding either lysozyme or RNase A. These results demonstrate that lysozyme was successfully imprinted into the MIP by UV free-radical polymerization, and the fabricated MIP was able to preferentially bind its template protein.     

First principles density functional study of the adsorption and dissociation of carbonyl compounds on magnesium oxide nanosurfaces

The adsorption and dissociation of three carbonyl compounds, formaldehyde, acetaldehyde, and acetone, on the magnesium oxide nanosurface, consisting of four stacked (MgO)3 hexagons, is investigated by first principles density functional theory (DFT). In the case of formaldehyde, strongly chemisorbed species, with carboxylate-like structures, are initially formed. These may subsequently undergo heterolytic cleavage of an aldehyde C-H bond to form formate ions involving a surface oxide ion and a hydride ion adsorbed over the magnesium dication [(MgH+)(HCOO-)]. For acetaldehyde, besides this reaction leading to the formation of acetate, the methyl hydrogen of the adsorbed species also tends to attach itself to a surface oxide ion, yielding surface hydroxyl ions and adsorbed [CH2=C(H)OMg]+. These results are in accord with our previous experimental and theoretical results. In particular, the shift of the aldehyde C-H vibration band to higher frequency and the appearance of OH bands in the infrared spectrum are clearly accounted for. For acetone, the mechanism is found to be similar, i.e., a methyl hydrogen shift to yield surface enolate. Again, this is in agreement with experimental studies.     

Structural,electronic, and reactivity parameters of some triorganotin(IV) carboxylates: a DFT analysis

The present work explores the probable parameters responsible for the potent anticancer activity of tin-based organometallic compounds. The characteristic structural, electronic, and reactivity features of some recently synthesized triorganotin(IV) carboxylates are identified by employing the density functional theory (DFT). The influence of solvent on these parameters is analyzed. In general, the stability of the complex is found to be governed by the donor ligand, alkyl/aryl group at the tin center, and the dielectric of the medium. Gallic acid, best known for its antioxidant and apoptosis inducing ability, forms the most stable complexes with tetrahedral geometry. The NBO analysis, frontier orbitals, and various reactivity indices of the complexes are discussed in detail. The most reactive sites on the organotin complexes are also predicted.