Organic transformation of lignin into mussel-inspired glues: next-generation 2K adhesive for setting corals under saltwater

The 2-methoxyphenol units (G-units) in lignin are modified by demethylation and oxidation to provide the activated lignin as one part of an advanced biobased two-component (2K) adhesive system, which exhibits promising shear strengths in dry and underwater applications. The activation of lignin is straightforward and generates quinones via demethylation and periodate oxidation. These act as Michael acceptors and react smoothly with multi-thiol-star polymers to yield thiol-catechol connectivities (TCCs). The mussel-inspired material platform acts as a very robust and versatile adhesive, combining low-cost and readily available lignin with multi-thiols to achieve outstanding adhesion strengths of up to 15 MPa in dry application. In particular, the 2K system is compatible with the marine biological environment and shows no acute toxicity to sensitive organisms such as fish eggs. Thus, one possible application of this material could be an adhesive for setting temperature-resistant corals in damaged reefs.Peer Reviewe

Magnetic Properties of Barium Hexaferrite Powders

In this paper, the magnetic properties of unsubstituted and substituted barium hexaferrite powders are examined. The powders were prepared by the glass crystallization method and characterized geometrically by electron microscopy, and magnetically by measurements of remanence curves. From an analysis of the energy barrier distributions determined from the differential of the primary remanence curves, it is shown that changing the substitution level influences the effective mean anisotropy field of the particles. Consequently this influences the magnetic microstructure as the coupling between the easy axis and the moment of the particle changes. Transverse susceptibility measurements were also made to obtain the values of the anisotropy field which are compared to VSM measurements. © 1994