Bicyclic Guanidine Promoted Mechanistically Divergent Depolymerization and Recycling of a Biobased Polycarbonate.

We here report the organocatalytic and temperature-controlled depolymerization of biobased poly(limonene carbonate) providing access to its trans-configured cyclic carbonate as the major product. The base TBD (1,5,7-triazabicyclo[4.4.

Synthesis of Biorenewable Terpene Monomers Using Enzymatic Epoxidation under Heterogeneous Batch and Continuous Flow Conditions.

A commercially available from immobilized onto a macroporous support (Novozym 435) has been employed in the presence of HO as a benign oxidant for the epoxidation of various biorenewable terpenes. This epoxidation protocol was explored under both heterogeneous batch and continuous flow conditions. The catalyst recyclability was also investigated demonstrating good activity throughout 10 cycles under batch conditions, while the same catalyst system could also be productively used under continuous flow operation for more than 30 h.

Extended -range small-angle neutron scattering to understand the morphology of proton-exchange membranes: the case of the functionalized syndiotactic-polystyrene model system.

Semi-crystalline polymers exhibit microphase separation into crystalline and amorphous domains characterized by multiple structural levels with sizes ranging from ångströms to hundreds of nanometres. The combination of small-angle (SANS) and wide-angle (WANS) neutron scattering on the same beamline enables reliable characterization of such materials under application-relevant conditions, with the unique advantage of contrast variation by controlled labelling, allowing the structure of such multi-component systems to be resolved in detail. This paper reports a structural analysis performed on deuterated polymer membranes based on syndiotactic polystyrene (sPS) using an extended -range SANS and WANS combination, always with the same neutron scattering instrument, either a pinhole SANS diffractometer installed at a research reactor or a 'small- and wide-angle' time-of-flight diffractometer installed at a neutron spallation source.

[OSSO]-Type Chromium(III) Complexes for the Reaction of CO with Epoxides.

In this work, four new mononuclear Cr(III) complexes (2-5) bearing bis-thioether-diphenolate, [OSSO]-type ligands, were synthesized and characterized. These complexes in combination with bis(triphenylphosphine)iminium chloride (PPNCl) promoted the coupling of CO with epoxides. Depending on the type of substrate and the conditions, the reaction results in the selective formation of either polycarbonate or cyclic carbonate.

Stereoregular Polymerization of Acyclic Terpenes.

The growing environmental pollution and the expected depleting of fossil resources have sparked interest in recent years for polymers obtained from monomers originating from renewable sources. Furthermore, nature can provide a variety of building blocks with special structural features (e. g.

Sustainable Myrcene-Based Elastomers via a Convenient Anionic Polymerization.

Soluble heterocomplexes consisting of sodium hydride in combination with trialkylaluminum derivatives have been used as anionic initiating systems at 100 °C in toluene for convenient homo-, co- and ter-polymerization of myrcene with styrene and isoprene. In this way it has been possible to obtain elastomeric materials in a wide range of compositions with interesting thermal profiles and different polymeric architectures by simply modulating the alimentation feed and the (monomers)/(initiator systems) ratio. Especially, a complete study of the myrcene-styrene copolymers (PMS) was carried out, highlighting their tapered microstructures with high molecular weights (up to 159.

The Effects of Temperature and Humidity on the Microstructure of Sulfonated Syndiotactic-polystyrene Ionic Membranes.

Polymeric membranes based on the semi-crystalline syndiotactic-polystyrene (sPS) become hydrophilic, and therefore conductive, following the functionalization of the amorphous phase by the solid-state sulfonation procedure. Because the crystallinity of the material, and thus the mechanical strength of the membranes, is maintained and the resistance to oxidation decomposition can be improved by doping the membranes with fullerenes, the sPS becomes attractive for proton-exchange membranes fuel cells (PEMFC) and energy storage applications. In the current work we report the micro-structural characterization by small-angle neutron scattering (SANS) method of sulfonated sPS films and sPS-fullerene composite membranes at different temperatures between 20 °C and 80 °C, under the relative humidity (RH) level from 10% to 70%.

Synthesis and Characterization of Syndiotactic Polystyrene-Polyethylene Block Copolymer.

The direct synthesis of syndiotactic polystyrene-block-polyethylene copolymer (sPS--PE) with a diblock structure has been achieved. The synthetic strategy consists of the sequential stereocontrolled polymerization of styrene and ethylene in the presence of a single catalytic system: cyclopentadienyltitanium(IV) trichloride activated by modified methylaluminoxane (CpTiCl/MMAO). The reaction conditions suitable for affording the partially living polymerization of these monomers were identified, and the resulting copolymer, purified from contaminant homopolymers, was fully characterized.

High Conversion of Styrene, Ethylene, and Hydrogen to Linear Monoalkylbenzenes.

1-Alkylbenzenes as a precursor of surfactants, can be produced from ethylene, styrene, and hydrogen. These intermediates, lacking tertiary carbons, are environmentally more benign than commercial ones that bear the aromatic ring linked to an internal carbon of the aliphatic chain. The one-pot synthesis of highly linear 1-alkylbenzenes (LABs) through the homogeneous catalysis of olefin poly-insertion from cheap and largely available reagents can be carried out with a high turnover and selectivity.