A Chitosan Derivative Containing Both Carboxylic Acid and Quaternary Ammonium Moieties for the Synthesis of Cyclic Carbonates.

Chitosan, a renewable feedstock, is modified and used as a catalytic support in the presence of potassium iodide. The system is highly efficient towards the incorporation of carbon dioxide (CO2 ) into epoxides. It demonstrates very good thermal stability and is recyclable more than five times without loss of activity. The optimal reaction conditions were determined using allylglycidyl ether as a model and extended to a wide range of other epoxides. Cyclic carbonates were obtained with very high yield in a few hours under mild conditions (2-7 bar≈0.2-0.7 MPa, 80 °C) and no solvent.

Photopolymerization study and adhesive properties of self-etch adhesives containing bis(acyl)phosphine oxide initiator.

OBJECTIVE: This paper investigates the photo-co-polymerization behavior of a blend of a diacrylamide (DEBAAP) with a phosphonylated acidic monomer using either bis(acyl)phosphine oxide or camphorquinone/amine as photo-initiator and studies the effect of variation of the structure of the phosphonylated acidic monomer on the shear bond strength to human dentin. METHODS: Photopolymerization kinetics has been assessed through the use of photo-DSC with either initiating system and with and without a phosphonic acid monomer, while the shear bond strengths (SBS) of dentin bonding agents formulated with several phosphonylated acidic monomers have been evaluated by macro SBS testing on human dentin. RESULTS: Photo-DSC results show that bis(acyl)phosphine oxide initiates a faster polymerization than camphorquinone/amine and that both photopolymerizations are accelerated by the phosphonic acid monomer. Similar results were obtained between adhesives based on camphorquinone/amine and a commercial adhesive (AdheSE, Ivoclar-Vivadent, Schaan, Liechtenstein). The best performances were obtained when BAPO was used as the initiator, in many cases far better than the commercial adhesive. Adhesive SEA6 based on difluoromethylphosphonic acid C demonstrated the best adhesion results of this study. Significance The bis(acyl)phosphine oxide photo-initiator causes faster photopolymerization of two-step self-etching dental adhesive, and its use could yield better bonding performance.