Polyesters synthesized through the alternating copolymerization of epoxides and cyclic anhydrides compose a growing class of polymers that exhibit an impressive array of chemical and physical ...properties. Because they are synthesized through the chain-growth polymerization of two variable monomers, their syntheses can be controlled by discrete metal complexes, and the resulting materials vary widely in their functionality and physical properties. This polymer-focused review gives a perspective on the current state of the field of epoxide/anhydride copolymerization mediated by discrete catalysts and the relationships between the structures and properties of these polyesters.
Childers et al explore stereoselective epoxide polymerization and copolymerization, focusing on basic concepts in stereoselective epoxide polymerization, stereoselective epoxide homopolymerization ...and stereoselective epoxide copolymerization with carbon dioxide.
Herein we show the formation of a polymer stereocomplex by mixing isotactic, regioregular chains of poly(propylene succinate) synthesized via the copolymerization of cyclic anhydrides and epoxides. ...The stereocomplex exhibits significantly improved thermal properties in comparison to the enantiopure parent polymers. We demonstrate that stereocomplexation is a route to a new class of semicrystalline polyesters with improved properties, produced from readily accessible starting materials.
Recent developments in polyester synthesis have established several systems based on zinc, chromium, cobalt, and aluminum catalysts for the ring-opening alternating copolymerization of epoxides with ...cyclic anhydrides. However, to date, regioselective processes for this copolymerization have remained relatively unexplored. Herein we report the development of a highly active, regioselective system for the copolymerization of a variety of terminal epoxides and cyclic anhydrides. Unexpectedly, electron withdrawing substituents on the salen framework resulted in a more redox stable Co(III) species and longer catalyst lifetime. Using enantiopure propylene oxide, we synthesized semicrystalline polyesters via the copolymerization of a range of epoxide/anhydride monomer pairs.
We report a comprehensive understanding of the stereoselective interaction between two opposite enantiomeric polyesters prepared from the regioselective copolymerization of chiral terminal epoxides ...and cyclic anhydrides. For many of the resultant polyesters, the interactions between polymer chains of opposite chirality are stronger than those of polymer chains with the same chirality, resulting in the formation of a stereocomplex with an enhanced melting point (T m) and crystallinity. The backbone, tacticity, steric hindrance of the pendant group, and molecular weight of the polyesters have significant effects on stereocomplex formation. Bulky substituent groups favor stereocomplexation, resulting in a greater rise in T m in comparison to the component enantiomeric polymers. The stereocomplex assembly of discrete (R)- and (S)-poly(phenyl glycidyl ether-alt-phthalic anhydride)s oligomers revealed that the minimum degree of polymerization required for stereocomplex formation is five. Raman spectroscopy and solid-state NMR studies indicate that stereocomplex formation significantly restricts the local mobilities of CO and C–H groups along the backbone of chains. The reduced mobility results in the enhanced spin–lattice relaxation time and both 1H and 13C downfield shifts due to the strong intermolecular interactions between R- and S-chains.
Efficient protocols for the addition of carbon-, sulphur- and nitrogen-nucleophiles to alpha , beta -unsaturated carbonyl compounds catalyzed by PS-BEMP have been reported. The adoption of ...solvent-free conditions (SolFC) was crucial for improving the efficiency of all the processes, while by using an organic reaction medium poor results were obtained. Addition reactions were performed by using equimolar amounts of reagents, and the products were isolated by simple filtration with the minimal amount of organic solvent. This approach allowed the E-factor, a measure of the waste of a reaction, to be minimized. Further waste minimization (95.7% compared to batch protocol) has been accomplished by defining a larger scale continuous-flow protocol operating under SolFC.
We report the synthesis of a solvent processable, tetraalkylammonium-functionalized polyethylene for use as an alkaline anion exchange membrane (AAEM). The membranes are insoluble in both pure water ...and aqueous methanol (50 vol % water) at 50 °C but exhibit excellent solubility in a variety of other aqueous alcohols (e.g., 5 wt % AAEM in aqueous n-propanol, 50 vol % water). These solubility characteristics extend the potential utility of this system for use as both an AAEM and ionomer electrode material from a single polymer composition. The AAEMs generated are mechanically strong and exhibit high hydroxide and carbonate conductivities.
Efficient protocols for the addition of carbon-, sulphur- and nitrogen-nucleophiles to ,-unsaturated carbonyl compounds catalyzed by PS-BEMP have been reported. The adoption of solvent-free ...conditions (SolFC) was crucial for improving the efficiency of all the processes, while by using an organic reaction medium poor results were obtained. Addition reactions were performed by using equimolar amounts of reagents, and the products were isolated by simple filtration with the minimal amount of organic solvent. This approach allowed the E-factor, a measure of the waste of a reaction, to be minimized. Further waste minimization (95.7% compared to batch protocol) has been accomplished by defining a larger scale continuous-flow protocol operating under SolFC.
The polystyryl-BEMP-catalyzed additions of carbon-, sulphur- and nitrogen-nucleophiles to ,-unsaturated carbonyls have been reported under solvent-free conditions. Using SolFC continuous-flow reactors, E-factor has been dramatically reduced.
Obesity is associated with a chronic, low-grade, systemic inflammation that may contribute to the development of insulin resistance and type 2 diabetes. Resveratrol, a natural compound with ...anti-inflammatory properties, is shown to improve glucose tolerance and insulin sensitivity in obese mice and humans. Here, we tested the effect of a 2-year resveratrol administration on proinflammatory profile and insulin resistance caused by a high-fat, high-sugar (HFS) diet in white adipose tissue (WAT) from rhesus monkeys. Resveratrol supplementation (80 and 480 mg/day for the first and second year, respectively) decreased adipocyte size, increased sirtuin 1 expression, decreased NF-κB activation, and improved insulin sensitivity in visceral, but not subcutaneous, WAT from HFS-fed animals. These effects were reproduced in 3T3-L1 adipocytes cultured in media supplemented with serum from monkeys fed HFS ± resveratrol diets. In conclusion, chronic administration of resveratrol exerts beneficial metabolic and inflammatory adaptations in visceral WAT from diet-induced obese monkeys.
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•Resveratrol elicits transcriptional changes in visceral and subcutaneous WAT•Resveratrol exerts anti-inflammatory effects in visceral WAT of HFS-fed monkeys•Resveratrol’s anti-inflammatory effect coincides with improved insulin sensitivity•Adipocytes play a key role in the adaptations evoked by resveratrol
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