Catalytic Activity of Boron-Beta Zeolite Modified with Indium in the Epoxidation of Cinnamyl Alcohol

Liquid-phase epoxidation of cinnamyl alcohol was carried out with hydrogen peroxide as oxidizing agent using indium-containing boron- and aluminium-beta zeolites. It was proved that InO⁺ ions, created by oxidation of univalent indium cations incorporated into beta zeolite by reductive solid-state ion exchange, play an important role in the activation of hydrogen peroxide. The indium-hydroperoxo complex formed in beta zeolite pores was found to be accessible by the bulky cinnamyl alcohol molecules. Among the applied catalysts In/H[B]-beta (containing 7.6% In₂O₃/g) showed the highest selectivity in cinnamyl alcohol epoxidation.     

Cobalt‐Mediated Radical Polymerization of Vinyl Acetate in Miniemulsion: Very Fast Formation of Stable Poly(vinyl acetate) Latexes at Low Temperature

Summary: Poly(vinyl acetate) macroinitiators end‐capped by a Co(acac)₂ complex (PVAc–Co(acac)₂), prepared in bulk by cobalt‐mediated radical polymerization (CMRP), are used for the controlled radical polymerization of vinyl acetate in miniemulsion to give high‐molecular‐weight polymers and high monomer conversion. Stable poly(vinyl acetate) latexes with solid contents ranging from 25 to 30 wt.‐% are prepared within unusually short reaction times (∼1 h) at low temperatures (0–30 °C).

SEC chromatograms for the PVAc–Co(acac)₂ macroinitiator and PVAc latex obtained under ultrasonication for 6 min at 0 °C (79% monomer conversion).     

Intelligent networks based on poly(oxyethylene)

Films of PEO and PEO blends were efficiently crosslinked by exposure to ultraviolet radiation with high-pressure mercury lamp. Photochemical crosslinking proceeded in the presence of photoinitiator such as benzophenone or pentaerythritol triacrylate. PEO networks obtained by UV irradiation in the presence of potassium salts (thiocyanate, perchlorate and triflate) as templates showed enhanced cation binding ability for Li⁺ and Na⁺ cations. Cationic networks were prepared from crosslinked PEO modified with ethyl methacrylate dimethyl dodecyl ammonium bromide. Stimuli-sensitive hydrogels (pH and temperature) were prepared from combinations of PEO and poly-N-isopropyl acryl amide, polyvinyl methyl ether, polyvinyl acetate and poly-2-vinyl pyridine subjected to UV irradiation.     

Crosslinked poly(ethylene oxide) for drug release systems

Three types of poly(ethylene oxide) (PEO)- based hydrogels have been synthesized and studied for drug release applications: γ-irradiated high molecular weight PEO, biodegradable polyether-polyester networks with malic acid as crosslinker of poly(ethylene glycol)s and amphiphilic PEO-based polyureas crosslinked with multifunctional isocyanates. Varying the length of the PEO chain and the type of the crosslinker, hydrogels with different swelling properties, loading capacities and release characteristics were obtained. A large number of pharmaceuticals (acebutolol. HCl, diclofenac. Na, procaine. HCl, phenobarbital.a, propranolol, etc.) were tested for a sustained release in different media (pH=1.2, 6.5, 7.4). Most of them # gave reasonable retarded release profiles for 8 hours when incorporated before the γ-irradiation crosslinking of PEO. While amphiphilic hydrogels were found to be suitable for hydrophobic solutes, the biodegradable PEO-based polyester ones affected predominantly the release of water-soluble drugs. No pH effect was found for the γ-irradiated PEO as a carrier in contrast to the strong pH dependence for the degradable polyester networks.     

Physicochemical and catalytic properties of grafted vanadium species on different mesoporous silicas

Vanadium modified mesoporous silicas type MCM-41, MCM-48, and SBA-15 are obtained by a solid state method. The samples are characterized and compared at the different steps of their preparation by X-ray diffraction, N(2)-physisorption, FTIR, UV-vis, XPS, and TG-TPR. Samples catalytic activity is tested in ethylacetate oxidation. Formation of various vanadium species, mainly isolated and small oligomeric ones, grafted to the support surface silanol groups, is observed. It is found that the state and the properties of the vanadium species depend on the porous characteristics of the silica host matrix. The nature of the catalytic active center in the ethylacetate oxidation is discussed.     

Study of multiblock polyamide-6/Poly-(isoprene) copolymers by positron annihilation spectroscopy

Positron annihilation lifetime spectroscopy (PALS) has been used to determine the free volume in multiblock polyamide-6/poly-(isoprene) copolymers (PA-6/PI), synthesized via activated anionic bulk copolymerization. The diisocyanate functionalized telechelic PI, blocked with caprolactam (CL) has been used as a commoner and an activator at the same time. The elastic PI block incorporated into the main chain of PA-6 affects the amorphous and crystal phase of the copolymer leading to changing in degree of crystallinity. The positron annihilation lifetime spectroscopy (PAL) and Doppler broadening of annihilation line (DBAL) technique in a set of pure PA-6 and PA-6/PI copolymers with two different compositions have been applied and evaluation of the size of free-volume holes (pores), localized mainly in the disordered regions of the PA-6/PI copolymer by measuring the o-Ps lifetime (τ₃) and o-Ps intensity (I₃) has been performed.