Coordinative Chain Transfer and Chain Shuttling Polymerization.

Coordinative chain transfer polymerization, CCTP, is a degenerative chain transfer polymerization process that has a wide range of applications. It allows a highly controlled synthesis of polyolefins, stereoregular polydienes, and stereoregular polystyrene, including (stereo)block as well as statistical copolymers thereof. It also shows a green character by allowing catalyst economy during the synthesis of such polymers. CCTP notably allows the end functionalization of both the commodity and stereoregular specialty polymers aforementionned, control of the composition of statistical copolymers without adjusting the feed, and quantitative formation of 1-alkenes from ethene. A one-pot one-step synthesis of the original multiblock microstructures and architectures by chain shuttling polymerization (CSP) is also an asset of CCTP. This methodology takes advantage of the simultaneous presence of two catalysts of different selectivity toward comonomers that produce blocks of different composition/microstructure, while still allowing the chain transfer. This affords the production of highly performant functional polymers, such as thermoplastic elastomers and adhesives, among others. This approach has been extended to cyclic esters' and ethers' ring-opening polymerization, providing new types of multiblock microstructure. The present Review provides the state of the art in the field with a focus on the last 10 years.

Bioactivity of Isostructural Hydrogen Bonding Frameworks Built from Pipemidic Acid Metal Complexes.

We report herein three novel complexes whose design was based on the approach that consists of combining commercially available antibiotics with metals to attain different physicochemical properties and promote antimicrobial activity. Thus, new isostructural three-dimensional (3D) hydrogen bonding frameworks of pipemidic acid with manganese (II), zinc (II) and calcium (II) have been synthesised by mechanochemistry and are stable under shelf conditions. Notably, the antimicrobial activity of the compounds is maintained or even increased; in particular, the activity of the complexes is augmented against Escherichia coli, a representative of Gram-negative bacteria that have emerged as a major concern in drug resistance. Moreover, the synthesised compounds display similar general toxicity (Artemia salina model) levels to the original antibiotic, pipemidic acid. The increased antibacterial activity of the synthesised compounds, together with their appropriate toxicity levels, are promising outcomes.

Eco-friendly fabricated multibioactive Ca(II)-antibiotic coordination framework coating on zinc towards improved bone tissue regeneration.

Zinc is a biodegradable candidate material for bone regeneration; however, concomitant implant-related infection and rejection require new solutions to raise the biomedical potential of zinc. Functionalization towards localized drug administration with bioactive frameworks can be a solution. It is herein reported for the first time an eco-friendly approach for coating zinc with multibioactive antibiotic coordination frameworks (ACF). ACF1, a new 1D framework with deprotonated nalidixic and salicylic acids, obtained by mechanochemistry, results from the coordination of Ca(II) centers to the organic acids anions. To maximize ACF1 loading and cells' adhesion, the surface area was increased by creating a porous 3D Zn layer. A coverage of ∼70% of the surface with ACF1, achieved by electrophoretic deposition in an aqueous solution, preserved the desired Zn degradation as |Z| in the order of 103 Ω.cm2 is attained for both bare and coated samples in physiological conditions. The bioactivities of the ACF1 powder are a strong antibacterial activity against Escherichia coli (MIC of 1.95 µg/mL) and weaker against Staphylococcus aureus (MIC of 250 µg/mL), while osteoblasts' cytocompatibility is achieved for concentration ranging between 10 and 100 µg/mL. In its coating form, the degradation of Zn coated with ACF1 results in nalidixic acid release, which may convey antibacterial activity to the implant. The osteoinduction observe over this new biomaterial relates to the precipitation of an apatite layer built from the Ca(II) of ACF1. The work described herein, where unexplored eco-friendly approaches were used, presents a new trend for the design of multibioactive coatings on bioresorbable metallic materials.