Efficient Approach for the Synthesis of Novel Functionalized Isoxazolines from Limonene

New functionalized isoxazolines were effeciently and easily prepared from limonene. The procedure involves a peri‐ and regioselective 1,3‐dipolar cycloaddition of nitrile oxides on the monoterpene external double bond, followed by a highly chemoselective RuCl₃‐NaIO₄ oxidative cleavage of the internal one. All the newly prepared isoxazolyl‐ketoacids were fully characterized from their spectroscopic data.     

Total Oxidation of ch4 on Iron-Promoted tin Oxide:Novel and Thermally Stable Catalysts

A series of Sn-Fe binary oxide catalysts with different Sn/Fe mole ratios were prepared by the combination of redox reactions and coprecipitation methods, and used in CH₄ deep oxidation. It is found that Sn-Fe binary catalysts show higher activity than pure SnO₂ and Fe₂O₃. XRD and BET surface area results illustrate that the binary catalysts have lower crystallinity and higher surface areas than the pure samples. Furthermore, TPR and XPS results demonstrate that more active oxygen species are formed in the Sn-Fe binary samples. Indeed, these could be the predominant reasons leading to the enhanced CH₄ oxidation activity of the Sn-Fe binary catalysts.     

Sharp Hydrophilicity Switching and Conformality on Nanostructured Surfaces Prepared via Initiated Chemical Vapor Deposition (iCVD) of a Novel Thermally Responsive Copolymer

A novel thermally responsive copolymer p(NIPAAm‐co‐DEGDVE) is synthesized using the substrate independent method of iCVD and exhibits a sharp lower critical solution temperature (LCST) transition centered at ≈28.5 ± 0.3 °C determined via quartz crystal microbalance measurements with dissipation monitoring (QCM‐D). Swelling with water below the LCST produces a reversible change of ≈3× in film thickness. The layer is conformal on nanostructured surfaces including MWCNT forests and electrospun nanofiber mats. Modified planar substrates exhibit ≈30°change in static contact angle over the LCST, while through conformal coating on nanostructured substrates changes in static contact angle up to 135° are achieved. Additionally, coated surfaces exhibit temperature sensitive BSA adsorption measured by QCM‐D and is reversible as shown through fluorescence imaging of a coated electrospun nanofiber mat.

     

A Novel Approach to Population Balance Modeling of Reactive Polymer Modification Leading to Branching

The mathematical treatment of polymer modification systems, described by population balances containing convolution is discussed. The two‐dimensional case (molecular weight vs. number of branch points) was considered by utilizing approximations of distributions, expanding them in terms of Gaussian basis functions. Three branching reactions were addressed: chain backbone to chain end point coupling; three‐functional coupling of chain ends; and crosslinking. The results were compared to those of Monte Carlo (MC) simulations. Good agreement was observed, although the quality of a distribution as generated by the numerical approach is much better in view of the strong scatter in the MC data.

     

A Novel Three Component Reaction: The Synthesis of Stable,Highly Functionalized 1,4-Diionic Nitrogen Betaines

The protonation of a highly reactive 1,4-dipole generated in the reaction between pyridine or isoquinoline and dialkyl acetylenedicarboxylates by the acidic C-H group of (ethoxycarbonylmethyl) triphenylphosphonium bromide leads to a vinyl pyridinium cation derivatives, which undergo a carbon-centered Michael type addition with the conjugate base of the CH-acid to produce highly functionalized stable 1,4-diionic nitrogen betaines.     

Diels-Alder Approach to Highly Functionalized Tertiary α-Hydroxy Ketones: A Novel Route to the Hexahydrobenzofuran Portion of the Avermectins and Milbemycins

A highly regio- and stereoselective Diels-Alder reaction between dienophiles of type I and dienes of type II (Scheme 1) gives rise to Diels-Alder adducts of type III . Upon treatment with BF₃.Et₂O, these adducts are smoothly converted into the corresponding enones (Scheme 6). Under mild acidic conditions, enone (±)- 33 gave bicyclic diketone (±)- 34 via an intramolecular Michael-type addition. Diketone (±)- 34 has the correct relative configuration and a suitable ketone function at C(6) for further conversion into the hexahydrobenzofuran portion of the avermectins and milbemycins.     

A Novel Approach to Magnetic Nanoadsorbents with High Binding Capacity for Bovine Serum Albumin

Magnetic nanoadsorbents using Fe₃O₄ nanoparticles as cores and poly(methyl acrylic acid) (PMAA) as ionic exchange groups were prepared through our novel approach. Two steps were involved in this approach: the first was to functionalize the magnetic nanoparticles (MNPs) with methacrylate double bonds via the combination of ligand exchange and condensation of methacryloxypropyltrimethoxysilane(MPS); the second was to graft PMAA chains onto the surface of MNPs through radical polymerization. The success of the various surface functionalization steps was ascertained using FTIR and XPS. The as‐synthesized PMAA‐coated MNPs were effective in binding bovine serum albumin (BSA) with a high capacity of 1 300 mg · g⁻¹.

     

Novel Biocatalysts by Chemical Modification of Known Enzymes: Cross-Linked Microcrystals of the Semisynthetic Peroxidase Seleno-Subtilisin

The linkage of lysine residues on the surfaces of subtilisin crystals (NH₂-Enz; see Scheme) with glutardialdehyde affords an immobilized biocatalyst of high stability and purity. The replacement of the serine OH group in the active site (Enz-OH) by SeO₂H leads to new activity as a peroxidase. Thus for the first time, chemical enzyme engineering has resulted in a biocatalyst with a modified peptide framework as well as a new catalytically active site. This methodology combines reasonable substrate selectivity of a semisynthetic enzyme with the exceptional stability of cross-linked enzyme crystals.     

A Novel Approach for the Surface Modification of Polymeric Membrane with Phospholipid Polymer

A new economic and convenient method to modify the surface of microporous polypropylene (PP) membranes with phospholipid polymer was given. The process included the photo-irradiated graft polymerization of N,N-dimethylaminoethyl methacrylate (DMAEMA) and the ring-opening reaction of the grafted polyDMAEMA with 2-alkyloxy-2-oxide-1,3,2-dioxo-phospholanes (AOP). Four AOPs, whose alkyloxy groups consisted of dodecyl, tetradecyl,hexadecyl and octadecyl moieties, were used to convert the grafted polyDMAEMA to phospholipidpolymers. FT-IR spectra confirmed the chemical change of membrane surface. Platelets adhesion experiment indicated that PP membrane with excellent blood compatible surface could be fabricated by this method.     

A Novel Approach to Prepare a Gradient Polymer with a Wide Damping Temperature Range by In‐Situ Chemical Modification of Rubber During Vulcanization

Summary: Based on the fact that rubber can be chemically modified by sulfur, and sulfur can diffuse into rubber driven by a concentration gradient and chemical reaction, a new approach for the preparation of a polymer with a gradient from rubbery to glassy phase has been developed using the sulfur‐vulcanization reaction of rubber. The gradient polymer obtained exhibits a wide transition range spanning over 100 °C with a peak half‐width of 69 °C. The mechanism of forming the gradient structure is also discussed.

The gradient polymer exhibits a broad tan δ width from −60 to 76 °C with the peak half‐width spanning about 69 °C, indicating a wide damping temperature range.     

Poly(vinyl alcohol) Chains Grafted onto the Surface of Copper Oxide Nanoparticles: Application in Synthesis and Characterization of Novel Optically Active and Thermally Stable Nanocomposites Based on Poly(amide-imide) Containing N-trimellitylimido-L-valine Linkage

Green polymer nanocomposites (NCs) show unique properties of combining the advantages of nanofillers and organic polymers. In this study, in order to control the dispersion of nanoparticles (NPs) in a polymer matrix, first, poly(vinyl alcohol) (PVA) as a green modifier was grafted on the surface of the CuO NPs to obtain CuO-PVA nanohybrid. Then poly(amide-imide) (PAI) was synthesized by the direct step growth polymerization of N-trimellitylimido-L-valine and 4,4′-methylenebis(3-chloro-2,6-diethylaniline) in ionic liquid medium. Finally, CuO-PVA hybrids were incorporated into the PAI matrix using ultrasonic technique for the preparation of PAI/CuO-PVA NCs. The obtained PAI/CuO-PVA NCs were characterized by different methods. The results of thermogravimetric analysis showed that thermal stability of the NCs was enhanced by incorporation of CuO-PVA nanohybrid compared to the pure PAI.     

FeCl3-Catalyzed Cascade Reaction: An Efficient Approach to Functionalized Coumarin Derivatives

An efficient and environmentally benign synthesis of 3-substituted or 3,4-disubstituted coumarins was accomplished via iron(III) chloride–catalyzed cascade reactions of salicylaldehydes and activated methylene compounds. The reaction preceded cleanly under mild reaction conditions to provide the desired coumarin derivatives in good to excellent yields.     

Polymerization of rac‐Lactide Using Achiral Iron Complexes: Access to Thermally Stable Stereocomplexes

Enantiopure poly(lactic acid) (PLA) can form stereocomplexes when enantiomeric PLA chains are mixed in equivalent amounts. Such materials provide interesting features that might be suitable for numerous applications. Despite several advantages, the main drawback of PLA is its narrow window of processing, thus limiting its use for industrial applications. Reported herein are achiral iron complexes, that are highly active, productive, and stereoselective under mild reaction conditions for the ring‐opening polymerization of lactide. The corresponding catalytic systems enable the production of stereoblock polymers with high molecular weights, allowing the formation of thermally stable and industrially relevant stereocomplexes.     

Filled Polysilsesquioxanes: A New Approach to Chemical Sensing

Summary : In an attempt to investigate new polymeric materials as constituents of an e-nose we focus our attention on a new emerging class of versatile three-dimensional polyhedral silicon polymers, called polysilsesquioxanes, containing nanosized inorganic cages. Such hybrid amphiphilic materials offer exceptional opportunities to create composites with singular properties. In particular we found that the polyhedral organosilsesquioxane (POSS) cages covalently attached to the polymer backbone as side-chain act as an “internal” filler with a nanometric homogeneous dispersion. We show how it is possible to fabricate sensing devices based on selected POSS matrix and, by a suitable choice of other “external” home-made fillers, (e.g. graphite, copper, silicon, zinc and their alloys) obtained by mechanical milling the response of the resulting composites towards different classes of compounds can be tuned. In particular we fabricated a new high sensitive relative humidity device, exhibiting a fivefold response change for relative humidity changing in the range 0% to 100%. This behaviour can not be modelled on the basis of the matrix swelling operating mechanism. Rather, the combined effect of the matrix and the filler has to be invoked in order to explain the formation of nanopores inside the material that are responsible of the porous behavior of our sensors.