Calixarenes are cyclic oligomers obtained by condensation of suitable p-functionalised phenols with formaldehyde, usually allowing for the synthesis of the well known small calixarenes (including up ...to eight phenolic subunits). We report here the discovery of much larger members of this family, exhibiting sizes up to 90 phenolic subunits: the giant calixarenes. These macrocycles are obtained according to simple, easily scalable processes, in yields up to 65%. We show that the formation of these giant macrocycles is favored by an oxygen-containing-group at the para-position of the starting phenol, high concentrations of heavy alkaline bases (rubidium or cesium hydroxides) and long reaction times. A mechanism is proposed to rationalize these observations. These giant macrocycles can also be obtained in the quasi-solid state, opening interesting perspectives in the field of calixarenes chemistry. Along with their intrinsic fundamental interest, these objects are also opening interesting applicative potentialities.
Well-defined phosphonate-functionalized polycarbonate with low dispersity (
= 1.22) was synthesized using organocatalyzed ring-opening polymerization (ROP) of novel phosphonate-based cyclic monomers. ...Copolymerization was also performed to access different structures of phosphonate-containing polycarbonates (PC). Furthermore, phosphonate-functionalized PC was successfully synthesized using a combination of ROP and post-modification reaction.
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•Synthesis of STFSI-functionalized monomers by using “Michael-addition” onto vinyl-STFSI.•Efficient addition of diallylamine, dipropargylamine, dimethylmalonate and diethylmalonate ...onto vinyl-STFSI.•Synthesis of STFSI-based polymers via step-growth polymerization technique.
Sulfonyl(trifluoromethylsulfonyl) imide anion (STFSI, SO2N(−)SO2CF3) is one of the most important sulfonimide groups for organic and material synthesis. However, the synthesis of STFSI-functionalized monomers and related polymers is still a problematic issue, comprising multi-step and complex synthetic processes. To overcome this drawback, we developed a robust and versatile strategy to prepare original STFSI-based monomers using the “Michael addition” reaction conducted in the presence of vinyl sulfonyl(trifluoromethylsulfonyl)imide and either an amine or a malonate derivative. Furthermore, the synthesized monomers were used to prepare the corresponding STFSI-functionalized polymers using step-growth polymerization with potential applications as electrolytes.
Radical chain end functionalization of polystyrene previously prepared by NMP using the SG1 nitroxide was investigated. Hydroxy-functional polystyrenes were easily prepared by two different pathways: ...via an exchange with TEMPO nitroxide followed by a Zn/AcOH reduction or via a radical hydroxylation using the in situ preparation/reduction of the corresponding hydroperoxide. The introduction of a bromine end group was performed by radical bromination under mild conditions using ethyl 2-bromoisobutyrate as bromine transfer agent. The latter polymer was further reacted with NaN3 and also used as a macroinitiator to prepare PS-b-PMMA by ATRP to confirm the chemical post-transformation. Azide-functional polystyrenes were also prepared by a one-step radical azidation reaction using ethanesulfonyl azide. In all cases, the chemical transformations were followed by both liquid chromatography at the critical condition in pure eluent and Maldi-Tof MS.
Although most monomers can polymerize through different propagation pathways, polymerization‐initiating systems that can switch from one mode to another are rare. In this study, we demonstrate that ...enamine‐based organic electron donors (OEDs) constitute the first systems able to initiate either free‐radical or anionic polymerization under simple, mild, and safe conditions. While direct electron‐transfer reduction of monomers by OEDs results in the initiation of anionic chain‐growth polymerization, introduction of a competing oxidant with a higher reduction potential than the monomer switches the former anionic propagation to a clean radical‐propagation process. The benefit of this dual‐mode activator is highlighted in the synthesis of an interpenetrating polymer network through simultaneous initiation of radical and anionic propagation processes.
Organic electron donors (OEDs) act as dual‐mode activators priming concomitant radical and anionic polymerizations to prepare interpenetrating polymer networks. OEDs can simultaneously reduce an oxidant to initiate a radical propagation and reduce a monomer to initiate an anionic propagation. These light‐, metal‐, and peroxide‐free redox systems open new horizons for the development of macromolecular architectures through dual chain‐growth modes.
Sunscreen oil-in-water emulsions containing few ingredients and two EU-authorized organic filters had been developed in an eco-friendly approach. Based on their photostability, spectroscopic ...features, and the lack of data on toxicity, BEMT (UVA/B range; bis-ethylhexyloxyphenol methoxyphenyl triazine) and DHHB (UVA; diethylamino hydroxybenzoylhexyl benzoate) were selected and incorporated at minimal concentrations to reduce the risk of impact on human health and coastal marine ecosystems. Despite the inconclusive results previously reported, the use of the w-soluble and largely available Na-lignosulfonate (LiS) had been reconsidered with success. Since BEMT and DHHB alone or in combination were not able to higher the sun protection factor (SPF) value at 50, results showed that it becomes possible by supplementing with LiS at 5% (w/w), ensuring stability, antiradical property, and a non-toxicity of the sun emulsion. After defining the range doses for the three components, minimizing concentrations was achieved by experimental design studies using a response surface methodology in which SPF values before and after irradiation has been considered. Consequently, an SPF30 and SPF50 emulsions containing only 9 and 12% total filter respectively and 5% LiS each had been developed. This high boosting effect led to discussions on how LiS interacts, suggesting the involvement of J aggregation, the formation of LiS micelles that would partly encapsulate the o-soluble filters, and the mode of adsorption at the solid-liquid interface of the poly(methyl-methacrylate) plate or the skin.
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•Evidence for lignosulfonate, the most available lignin, as an efficient booster of SPF in sunscreen emulsion.•Application to an eco-design concept by minimizing UV filter concentrations to diminish risks (health, marine ecosystems).•Two photostable, a UVA/B and a UVA organic filter are formulated with lignosulfonate to ensure maximal protection (SPF 50).•Experimental design and response surface methodology led to two stable emulsions containing few ingredients, SPF30 and SPF50.•Lignin-sunscreen interactions are discussed.
Polymerization reactions with organic electron donors (OED) as initiators are presented herein. The metal‐free polymerization of various activated alkene and cyclic ester monomers was performed in ...short reaction times, under mild conditions, with small amounts of organic reducing agents, and without the need for co‐initiators or activation by photochemical, electrochemical, or other methods. Hence, OED initiators enabled the development of an efficient, rapid, room‐temperature process that meets the technical standards expected for industrial processes, such as energy savings, cost‐effectiveness and safety. Mechanistic investigations support an electron‐transfer initiation pathway that leads to the reduction of the monomer.
Off to a good start: The metal‐free polymerization of various activated alkenes and cyclic esters occurred rapidly under mild conditions in the presence of organic electron donors (OED) as initiators and without the need for co‐initiators or external activation methods (see picture). The simple and efficient room‐temperature process meets the technical standards of low energy consumption, cost‐effectiveness, and safety.
An analytical methodology with mass spectrometry as the core technique was developed for precise characterization of end groups, size, and co-monomeric composition of poly(lactic-co-glycolic acid) ...(PLGA) copolymers, as a preliminary step to qualify their biodegradability. Four PLGA samples were studied, with GA molar content varying from 0 to 50% and M w ranging from 18 to 75 kg mol–1 according to the supplier. Size exclusion chromatography (SEC) and liquid state nuclear magnetic resonance (NMR) were used as either complementary or validation techniques. As confirmed by tandem mass spectrometry (MS/MS) experiments, macrocycles were most prominent in the low mass range. Nevertheless, elemental compositions derived from high resolution (HR) mass measurements of linear species were consistent with chain terminations revealed by NMR. Off-line coupling of SEC with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) permitted calibration curves to be built based on absolute molecular weights and, although slightly overestimated, so-obtained M n and M w values compared well with SEC and NMR results. Homogeneity of the co-monomeric content of all chains within each PLGA sample was demonstrated using surface-assisted laser desorption/ionization in a reactive mode (reactive-SALDI), a newly developed technique that takes advantage of residual acid on desorption ionization using through-hole alumina membrane (DIUTHAME) chips to induce dissociation of high-molecular-weight polymers containing cleavable C–O bonds. All HRMS data were best handled with Kendrick analysis, which helped reveal minor species and allowed automated computation of congested mass spectra.
A catalyst/initiator‐free radical addition reaction performed under mild conditions (water, 30 °C) with high yields is reported for the first time. This reaction implies simple pH‐mediated ...alkoxyamine dissociation followed by addition onto olefinic substrates. The versatility and relevance of this selective reaction for macromolecular conjugation and engineering are shown through the syntheses of block copolymers, as well as hydrogels containing in situ‐loaded proteins, which could retain biological activity. This contrasts with standard thermal radical conditions that lead to complete protein inactivation.
Cata‐less: The first catalyst‐free and initiator‐free radical addition under mild conditions is presented, offering versatile syntheses of block copolymers and in situ‐loaded protein hydrogels.
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