Search

Within bioplastics, natural poly(3‐hydroxybutyrate) (PHB) stands out as fully biocompatible and biodegradable, even in marine environments; however, its high isotacticity and crystallinity limits its mechanical properties and hence its applications. PHB can also be synthesized with different tacticities via a catalytic ring‐opening polymerization (ROP) of rac‐β‐butyrolactone (BBL), paving the way to PHB with better thermomechanical and processability properties. In this work, the catalyst family is extended based on aluminum phenoxy‐imine methyl catalyst [AlMeL2], that reveals efficient in the ROP of BBL, to the halogeno analogous complex [AlClL2]. As well, the impact on the ROP mechanism of different initiators is further explored with a particular focus in dimethylaminopyridine (DMAP), a hardly studied initiator for the ROP of BBL. A thorough mechanistic study is performed that evidences the presence of two concomitant DMAP‐mediated mechanisms, that lead to either a DMAP or a crotonate end‐capping group. Besides, in order to increase the possibilities of PHB post‐polymerization functionalization, the introduction of a side‐chain functionality is explored, establishing the copolymerization of BBL with β‐allyloxymethylene propiolactone (BPLOAll), resulting in well‐defined P(BBL‐co‐BPLOAll) copolymers. [ABSTRACT FROM AUTHOR]

This communication reports the synthesis and X-ray characterization of a new mononuclear aluminium compound exhibiting an intramolecular σ-hole triel bonding interaction. It is compared with a dinuclear aluminium compound, previously reported by us, where the aluminium atoms participate in two concurrent σ-hole triel bonding interactions. To our knowledge, such behaviour has not been previously described in the literature. [ABSTRACT FROM AUTHOR]

New aluminium-alkali metal heterometallic compounds using the bulky ligand OAr = 2,6-bis(diphenylmethyl)-4-tert-butylphenoxide have been synthesized and characterized. The species obtained, [MAlMe3(OAr)] (M = Li(2a), Na(2b), K(2c)) and [MAlMe2(OAr)2] (M = Li(3a), Na(3b), K(3c)), include some of the few heterobimetallic examples of aluminate complexes with O-donor ligands described so far. Their activity in polymerization towards a difunctional monomer, such as Glycidyl Methacrylate (GMA), was evaluated. The compounds were revealed to be able to polymerize the acrylate groups via vinyl polymerization. Interestingly, the homometallic counterparts [AlXMe(OAr)] (X = Cl, Me), previously described by us, are very active in ROP processes of GMA. The combined polymerization process using both catalysts has also been explored to obtain a polymeric material with an exciting macromolecular architecture. [ABSTRACT FROM AUTHOR]

Perfluorooctanoic acid (PFOA) is a persistent organic pollutant and widespread in the environment. Three hosts have been synthesized based upon the formation of a fluorous cavity and hydrogen bonding receptors with the aim of extracting PFOA from water into organic solvents. The hosts based upon a calix[4]arene functionalized at the lower rim with amide groups and fluorous ponytails are effective for the quantitative removal of PFOA. Modification to a partial cone or a trisaminoamine framework reduces the conformational rigidity and lowers the extraction efficiency. A comprehensive NMR spectroscopic analysis both in solution and the solid state, along with other characterization techniques, has elucidated the stoichiometry of the host:guest species and the binding constants have been measured. A computational study has given further insight into the binding modes and corroborated the spectroscopic measurements. [ABSTRACT FROM AUTHOR]

Abstract: New aluminum compounds of the type [AlXMe(OAr)]n [X=Me (1), Cl (2)] bearing the bulky ligand OAr=2,6‐bis(diphenylmethyl)‐4‐tert‐butylphenoxide were synthesized and characterized in the solid state and in solution. These compounds are mononuclear in solution. Their catalytic activity in glycidyl methacrylate (GMA) polymerization was explored. This monomer contains two different functionalities, oxirane and methacrylate, and, hence, could give functionalized polymers by ring‐opening polymerization (ROP) or vinyl polymerization. Catalysts 1 and 2 could selectively polymerize the oxirane functionality in minutes at room temperature, leaving the methacrylate group intact. Remarkably, 1 and 2 are the most active catalysts in ROP processes of GMA described so far. [ABSTRACT FROM AUTHOR]

A recently reported combined polymerization process of glycidyl methacrylate, mediated by homometallic and heterobimetallic aluminium complexes, naturally produces nano-sized macromolecular assemblies. In this work, the morphological features and the rheological properties of these novel nanoassemblies are studied. The hydrodynamic sizes of the nanoparticles in the solution range from 10 to 40 nm (in numbers), but on a flat surface they adopt a characteristic thin disk shape. The dynamic moduli have been determined in a broad range of temperatures, and the time—temperature superposition applied to obtain master curves of the whole viscoelastic response from the glassy to the terminal regions. The fragility values obtained from the temperature dependence are of m ~40, typical of van de Waals liquids, suggesting a very effective packing of the macromolecular assemblies. The rheological master curves feature a characteristic viscoelastic relaxation with the absence of elastic intermediate plateau, indicating that the systems behaved as un-entangled polymers. The analysis of the linear viscoelastic fingerprint reveals a Zimm-like dynamics at intermediate frequencies typical of unentangled systems. This behaviour resembles that observed in highly functionalized stars, dendrimers, soft colloids and microgels. [ABSTRACT FROM AUTHOR]

[Display omitted] The antimicrobial lysozyme (Lys) was electrostatically incorporated to negatively charged crosslinked poly(glycidyl methacrylate) (c-PGMA) macromolecular assemblies. The resulting material was characterized by AFM, infrared spectra, water contact angle measurements and the staining with the primary amino specific dye fluorescamine. c-PGMA nanoparticles were successfully loaded with Lys reaching ratios of 27.3 ± 4.0 and 22.5 ± 1.7 mg Lys/g polymer for c-PGMA suspensions and functionalized glass substrates, respectively. Lys-loaded c-PGMA caused clear inhibition zones on S. aureus and E. coli in comparison to neat c-PGMA. c-PGMA functionalized surfaces were intrinsically resistant to colonization, but the incorporation of Lys added resistance to bacterial attachment and allowed keeping surfaces clean of bacterial cells for both strains. A relatively rapid release (24 h) of Lys was observed at physiological pH (7.4). In addition, c-PGMA functionalized substrates could be reloaded several times without losing capacity. c-PGMA macromolecular assemblies did not display cytotoxicity to human dermal fibroblasts as shown in 24 h MTT assays. This work demonstrated that c-PGMA assemblies display durable antibacterial activity, biocompatibility, and full reloading capacity with antimicrobial peptides. c-PGMA functionalized materials have potential application as nanocarriers for anti-infective uses. [ABSTRACT FROM AUTHOR]

This communication reports the synthesis and X-ray characterization of a new mononuclear aluminium compound exhibiting an intramolecular σ-hole triel bonding interaction. It is compared with a dinuclear aluminium compound, previously reported by us, where the aluminium atoms participate in two concurrent σ-hole triel bonding interactions. To our knowledge, such behaviour has not been previously described in the literature.