Propene and 1-Octene Hydroformylation with Silica-Supported, Ionic Liquid-Phase (SILP) Rh-Phosphine Catalysts in Continuous Fixed-Bed Mode

Supported ionic liquid-phase (SILP) catalysts were made by immobilizing Rh-monophosphine complexes of bis(m-phenylguanidinium)phenylphosphine 1 and NORBOS 2 ligands in 1-n-butyl-3-methylimidazolium hexafluorophosphate, [BMIM][PF₆], on a silica support. The catalysts were active in continuous gas- and liquid-phase hydroformylation of propene and 1-octene, exhibiting TOFs up to 88 h^-1 for SILP Rh-2 catalysts, while only low selectivities up to 74% n-aldehyde (n/iso ratio of 2.8) were obtained. This is the first example of continuous fixed-bed liquid-phase hydroformylation using SILP catalysts.     

Viscoelasticity in Polymer Films on Rigid Substrates

The viscoelasticity of two thermally crosslinked polymer coatings was examined in terms of relaxation of the applied stress after a sudden strain. Two different transient methods were utilized: flat‐ended cylindrical indentation testing of a polymer film on a rigid substrate and tensile testing of a corresponding free‐standing polymer film. The correlation between tensile and indentation tests was studied. The mechanical response of a viscoelastic layer deposited on a rigid substrate was investigated as a function of indentation depth. There was good agreement between the results of the tensile and indentation tests for thick film layers at moderate indentation depths. The findings indicate that the substrate influences the coating performance by reducing the viscous contribution to the stress response and amplifying the magnitude of the equilibrium modulus for large indentation depths. The indentation method utilized here was shown to be a potentially suitable tool for the determination of Poisson's ratio of polymer films.

     

Rheological properties of hyperbranched polymer/poly(ethylene terephthalate) reactive blends

The rheological properties in solution, in shear and in uniaxial elongation of poly(ethylene terephthalate) (PET) reacted together with hyperbranched polymers (HBPs) were investigated. Two different PET grades, of low and high molecular weights, were compounded with sub‐ to over‐stoichiometric concentrations of HBPs of second and fourth pseudo‐generation, and subsequently subjected to a solid‐state polycondensation (SSP). The formation of microgels, which occurs at high HBP concentration, gave rise to a large increase in melt elasticity and a related decrease in melt strength. At low HBP concentrations, the complex viscosity of the unreacted HBP/PET was considerably reduced, thus demonstrating a lubrication effect of the HBP molecules. During SSP, the intrinsic and shear viscosities exhibited a gradual increase, which was similar for both PET and HBP/PET blends, and was correlated to an increase in molecular weight, through linear‐chain extension and branching reactions. The elongational viscosity of the reactive blends was also increased as a function of reaction time, and this increase was much larger in the case of the HBP/PET blends. A 400% increase in melt strength of the PET was obtained by combining SSP and trace amounts of an HBP of second generation, without any decrease in drawability.     

Temperature-Dependent Re-alignment of the Short Multifunctional Peptide BP100 in Membranes Revealed by Solid-State NMR Spectroscopy and Molecular Dynamics Simulations

BP100 is a cationic undecamer peptide with antimicrobial and cell-penetrating activities. The orientation of this amphiphilic α-helix in lipid bilayers was examined under numerous conditions using solid-state ¹⁹F, ¹⁵N and ²H NMR. At high temperatures in saturated phosphatidylcholine lipids, BP100 lies flat on the membrane surface, as expected. Upon lowering the temperature towards the lipid phase transition, the helix is found to flip into an upright transmembrane orientation. In thin bilayers, this inserted state was stable at low peptide concentration, but thicker membranes required higher peptide concentrations. In the presence of lysolipids, the inserted state prevailed even at high temperature. Molecular dynamics simulations suggest that BP100 monomer insertion can be stabilized by snorkeling lysine side chains. These results demonstrate that even a very short helix like BP100 can span (and thereby penetrate through) a cellular membrane under suitable conditions.     

Mesoporous Natural Fiber Welded Cellulose Containing Silver Nanoparticles as a Recyclable Heterogeneous Catalyst

Silver nanoparticles (AgNPs) are presented within mesoporous natural fiber welded (NFW) cellulose and demonstrated as robust catalysts to reduce 4-nitrophenol using sodium borohydride. Growing AgNPs this way enables their retention within a nonderivatized, mesoporous, all-cellulose NFW composite. At an AgNP loading of 1.0 wt%, no leaching is observed during rinsing with polar and nonpolar solvents or any of 12 catalyst cycles and the cloth is easily retrievable and reusable. Comparatively, a 1.0 wt% AgNP loading on non-NFW cotton thread loses ≈95% of the starting Ag under similar conditions. Only at higher loadings is a very slow leaching observed in the NFW composite (<10% Ag loss). With a turnover frequency of 0.9 h^–1 (as compared to 2.2 h^–1 for the non-NFW cotton thread), the catalytic activity suffers only minor impedance from the NFW structure while affording significant promise in future applications for leach-resistant nonderivatized cotton (e.g., TiO₂ or photonic nanomaterials). Finally, it is shown that combustion of AgNPs-NFW composites creates Ag residues distinct from materials produced via combustion of AgNPs on non-NFW cotton. While the residues produced comprise Ag and residual carbon, this method is viable for producing metal “sponges” from monometallic and bimetallic NPs on mesoporous cellulose.     

A Method for Evaluating Lignin Mobility Distributions Obtained by Capillary Zone Electrophoresis

Abstract

The profile of the mobility distribution of lignin-containing samples depends on type of sample. To facilitate comparison, a procedure for determining the average mobility (μ_av), i.e. the average charge density, of lignin is presented. The procedure is applied to black liquor (Sb), isolated dissolved lignin (Sd) and isolated residual (Sr) lignin samples, obtained from flow-through kraft cooks of softwood. The μ_av of the isolated lignin samples is compared with the concentration of phenol and carboxyl groups and relative molecular size. As the cook proceeds the μ_av for a particular type of lignin sample increases, reflecting an increase in average charge density. The μ_av, measured at pH 12, decreases in the order Sd>Sb>Sr, except at the end of the cook, when the average charge densities of the Sb and Sr samples are similar. Associations between lignin and carbohydrate fragments are proposed to cause the lower mobility of black liquor compared to isolated dissolved lignin. Characterisations performed at pH 10 indicate that the isolated dissolved lignin samples may have a higher pK_a in the middle of the cook than the other samples.     

Detection of Pinosylvins in Solid Wood of Scots Pine Using Fourier Transform Raman and Infrared Spectroscopy

Abstract

Diffuse reflectance Fourier transform infrared (DRIFT) and near infrared (NIR) FT-Raman spectroscopy were used to detect pinosylvins in the wood of Pinus sylvestris L. trees. NIR FT-Raman spectroscopy offered the possibility of revealing pinosylvins simply by visual inspection of Raman spectra whereas DRIFT spectra needed a more complicated evaluation. Pinosylvin and resin acids from Scots pine were examined as to the possibility of their being the cause of observed spectral differences between sapwood and heartwood. Since pinosylvins are important compounds for the decay resistance of Scots pine wood, the detection of pinosylvins with Raman spectroscopy might be used to assess durability of wood products.     

STEAM DRYING OF WOOD CHIPS IN PNEUMATIC CONVEYING DRYERS

ABSTRACT

A model for a pneumatic conveying dryer is presented. Although the main emphasis is put on superheated steam drying of wood chips, it can be used for other porous materials as well

The model includes a comprehensive two-dimensional model for the drying of single wood chips which accounts for the main physical mechanisms occurring in wood during drying. The external drying conditions in a pneumatic conveying dryer were calculated by applying the mass, heat and momentum equations for each incremental step in dryer length. A plug flow assumption was made for the dryer model and the single particle and dryer models were solved in an iterative manner. The non-spherical nature of wood chips were accounted for by measuring the drag and heat transfer coefficients

Model calculations illustrate the complex interactions between steam, particles and walls which occur in a flash dryer. The drying rate varies in a very complex manner through the dryer. The internal resistance to mass transfer becomes very important in The drying of less permeable wood species such as spruce. Two effects were observed as the particle size was increased: firstly the heat transfer rate decreased, and secondly the residence time increased. To some extent, these effects compensate for each other, however, the net result is that larger chips have a higher final moisture content.     

Danger Control Programs Cause Tissue Injury and Remodeling

Are there common pathways underlying the broad spectrum of tissue pathologies that develop upon injuries and from subsequent tissue remodeling? Here, we explain the pathophysiological impact of a set of evolutionary conserved danger control programs for tissue pathology. These programs date back to the survival benefits of the first multicellular organisms upon traumatic injuries by launching a series of danger control responses, i.e., 1. Haemostasis, or clotting to control bleeding; 2. Host defense, to control pathogen entry and spreading; 3. Re-epithelialisation, to recover barrier functions; and 4. Mesenchymal, to repair to regain tissue stability. Taking kidney pathology as an example, we discuss how clotting, inflammation, epithelial healing, and fibrosis/sclerosis determine the spectrum of kidney pathology, especially when they are insufficiently activated or present in an overshooting and deregulated manner. Understanding the evolutionary benefits of these response programs may refine the search for novel therapeutic targets to limit organ dysfunction in acute injuries and in progressive chronic tissue remodeling.