International audienceOrganocatalysis has become an invaluable tool for polymer synthesis, and its utility has been demonstrated in ring-opening, anionic, zwitterionic, and group-transfer polymerizations. Despite this, the use of organocatalysis in other polymerization reactions such as step-growth polymerizations remains underexplored, relative to more traditional metal-based polymerizations. Recently, the use of organic bases such as guanidines, amidines, N-heterocyclic carbenes, and organic "strong or super-strong" Bronsted acids to catalyze the synthesis of metal-free polyurethanes has shown to be competitive to commercially widely used dibutyltin dilaurate and dibutyltin diacetate catalysts. This Perspective article highlights recent advances in organocatalyst design for isocyanate-based polyurethane synthesis with the aim of comparing the activity and selectivity of each of the new catalytic reactions to each other and the traditional metal-based catalysts. The article also draws attention to new trends in isocyanate-free polyurethane synthesis and the key role that organocatalysis is playing in these innovative polymerization processes

In this study, a new family of broad-spectrum antimicrobial polycarbonate hydrogels has been successfully synthesized and characterized. Tertiary amine-containing eight-membered monofunctional and difunctional cyclic carbonates were synthesized, and chemically cross-linked polycarbonate hydrogels were obtained by copolymerizing these monomers with a poly(ethylene glycol)-based bifunctional initiator via organocatalyzed ring-opening polymerization using 1,8-diazabicyclo[5.4.0]undec-7-ene catalyst. The gels were quaternized using methyl iodide to confer antimicrobial properties. Stable hydrogels were obtained only when the bifunctional monomer concentration was equal to or higher than 12 mol %. In vitro antimicrobial studies revealed that all quaternized hydrogels exhibited broad-spectrum antimicrobial activity against Staphylococcus aureus (Gram-positive), Escherichia coli (Gram-negative), Pseudomonas aeruginosa (Gram-negative), and Candida albicans (fungus), while the antimicrobial activity of the nonquaternized hydrogels was negligible. Moreover, the gels showed fast degradation at room temperature (4-6 days), which makes them ideal candidates for wound healing and implantable biomaterials.

The use of organocatalysts for the polymerization of ethylene brassylate, a commercially available, cheap, and renewable macro(di)lactone is reported for the first time. Ethylene brassylate was polymerized by ring-opening polymerization under bulk and solution conditions at 80 °C. Polymerizations were carried out in the presence of several organic catalysts, such as dodecylbenzenesulfonic acid (DBSA), diphenyl phosphate (DPP), p -toluenesulfonic acid (PTSA) a nd bases, 1 ,5,7triazabicyclo[4.4.0]dec-5-ene (TBD), 1,2,3-tricyclohexylguanidine (TCHG), and 1,2,3-triisopropylguanidine (TIPG), using benzyl alcohol as initiator. Results agreed with a ring opening polymerization process in which the rate of polymerization was accelerated by the catalysts presence in the order of TBD > PTSA > DBSA > DPP > TIPG > TCHG. Complementary computational studies supported the experimental results. The obtained poly(ethylene brassylate) aliphatic polyesters were characterized by NMR, SEC, MALDI-TOF, DSC, and TGA. They showed molecular weights ranging from 2 to 13 kg mol −1 and polydispersity index between 1.5 and 2. Poly(ethylene brassylate) is a semicrystalline polyester similar to poly(ε−caprolactone) with slightly higher melting and glass transition temperatures (T m = 69 °C, T g = −33 °C) and good thermal stability.

Single doses of both haloperidol and risperidone produce negative symptoms in normal individuals. Drowsiness may be an important confounding factor in the assessment of negative symptoms in antipsychotic trials.

A systematic study of acid organocatalysts for the polyaddition of poly(ethylene glycol) to hexamethylene diisocyanate in solution has been performed. Among organic acids evaluated, sulfonic acids were found the most effective for urethane formations even when compared with conventional tin-based catalysts (dibutyltin dilaurate) or 1,8-diazabicyclo[5.4.0]undec-7-ene. In comparison, phosphonic and carboxylic acids showed considerably lower catalytic activities. Furthermore, sulfonic acids gave polyurethanes with higher molecular weights than was observed using traditional catalyst systems. Molecular modeling was conducted to provide mechanistic insight and supported a dual activation mechanism, whereby ternary adducts form in the presence of acid and engender both electrophilic isocyanate activation and nucleophilic alcohol activation through hydrogen bonding. Such a mechanism suggests catalytic activity is a function of not only acid strength but also inherent conjugate base electron density.