Surface characteristics of block copolymer solutions and reaction mixture components as key elements to understanding of the behavior of block copolymer based hydrogenation catalyst

This work is devoted to the investigation of surface characteristics such as contact angle and surface tension of the poly(ethylene oxide)-block-poly(2-vinyl pyridine) (PEO-b-P2VP) block copolymer solutions. The block copolymer was used for the development of micellar and heterogenized selective Pd-containing hydrogenation catalysts. Besides, surface tension of solutions of a reactant (dehydrolinalool) and a product (linalool) were investigated as a function of solvent nature and composition. It was found that varying the solvent polarity allows tuning the access of the reactant to catalytic sites and the removal of the product from the micelle core. The surface tension measurements were in accordance with the results of the catalytic investigation. Among the investigated solvents the iso-propanol plus water mixture (30 vol.% of H2O) was found to provide the best catalytic properties, although such a complex solvent revealed higher surface tension than pure iso-propanol. In the case of heterogenized catalyst, a scheme of the block copolymer interaction with the SiO2 surface was proposed.