CS2 capture in the ionic liquid 1-alkyl-3-methylimidazolium acetate: reaction mechanism and free energetics.

Reaction pathways for CS2 and COS in the ionic liquid, 1-ethyl-3-methylimidazolium (EMI+) acetate (OAc-), are studied using the ab initio self-consistent reaction field theory (SCRF) and molecular dynamics (MD) computer simulations. It is found that while CS2 converts to COS nearly at the 100% level through S/O exchange with acetate, both conversion and capture processes are kinetically possible for COS, yielding CO2/thioacetate and 1-ethyl-3-methylimidazole-2-thiocarboxylate (EMI-COS)/acetic acid as reaction products, respectively. These findings are in excellent agreement with recent experimental observations in the closely related 1-butyl-3-methylimidazolium acetate (BMI+OAc-) ionic liquid system. Constrained ab initio MD indicates that the capture reaction of COS (and CS2 if allowed) proceeds in a concerted fashion; viz., proton transfer from EMI+ to OAc- and carboxylation of EMI+ by COS (and CS2) occur concurrently, analogous to the concerted pathway proposed recently for CO2 capture in the imidazolium acetate ionic liquid family. As N-heterocyclic carbene (NHC) is not required, the concerted mechanism is fully consistent with the experimental fact that NHC has not been detected directly in this ionic liquid family. Computational analysis further predicts that if NHC would be present in the ionic liquid, it would react with CS2 and produce 1-ethyl-3-imidazole-2-dithiocarboxylate, prior to the conversion of CS2 to COS. Since such a dithiocarboxylate compound was not detected experimentally, the present analysis lends support to the view that NHC is not formed in the pure imidazolium acetate ionic liquid family.

Preparation of functional polyamine scaffolds via Mitsunobu post-polymerization modification reactions.

A Mitsunobu reaction of trifluoroacetamide (TFA amide) and alcohols is used in a postpolymerization modification process. The reaction is conducted on polystyrene (PSt) bearing 20 mol% TFA amide groups with 4-methyl benzyl alcohol in the presence of a N,N,N',N '-tetramethylazodicarboxamide and tributylphosphine as mediators. The Mitsunobu reaction on polymer proceeds efficiently, as confirmed by the obvious precipitation generation during the reaction and the conversion of TFA amide moiety reached 88.6% confirmed by 19 F NMR measurement, yielding PSt bearing tertiary TFA amide moieties. The obtained polymers featuring tertiary TFA amide moieties are deprotected in the presence of tetrabutylammonium hydroxide as a base to afford corresponding polymers featuring functionalized polyamine scaffolds with 92.5% conversion. In addition, the precise structural assignment is proven by synthesis and analysis of the model monomeric compounds and the respective model polymers.

Multicomponent reactions in polymer synthesis.

More participants, yet efficient reactions: Multicomponent reactions (MCRs) have found application in polymer chemistry both in the synthesis of multifunctional monomers and in post-polymerization modification. Examples include the Passerini three-component reaction, the Ugi four-component reaction, and the copper-catalyzed MCR.

GFN-xTB-Based Computations Provide Comprehensive Insights into Emulsion Radiation-Induced Graft Polymerization.

In this article, a deep insight into emulsion radiation-induced graft polymerization (RIGP) was obtained by computing explicit solvation free energies, conformational entropy, monomer radius and dipole moments with the state-of-the-art Conformer-Rotamer Ensemble Sampling Tool (CREST) package primarily at semiempirical GFN-xTB level. By leveraging the robustness of the CREST package, above parameters provided dynamic nature of methacrylate monomers with the consideration of realistic emulsion conditions. With the chemical and physical importance of the above results, CREST-determined explanatory variables sufficiently led to the building of the prediction models for the RIGP of methacrylate monomers. The machine learning model building resulted in effective reactivity predictions and unveiled important factors for the radiation-induced graft polymerization in a chemically interpretable fashion.

GFN-xTB-Based Computations Provide Comprehensive Insights into Emulsion Radiation-Induced Graft Polymerization.

Invited for this month's cover are the collaborating groups of Dr. Ryohei Kakuchi and Ms. Kiho Matsubara at Gunma University, Japan, Prof. Kei Takahashi at Fukuoka Institute of Technology and The Institute of Statistical Mathematics, Japan, Prof. Takeshi Matsuda at Hannan University, Japan, Dr. Noriaki Seko and Dr. Yuji Ueki at National Institutes for Quantum Science and Technology, Japan. The cover picture shows the machine learning-based optimization and interpretation of radiation-induced graft polymerizations under emulsion conditions based on realistic information for monomers calculated by the state-of-the-art semiempirical method. More information can be found in the Research Article by Kiho Matsubara, Kei Takahashi, Ryohei Kakuchi, and co-workers.

Confocal microscopic oxygen imaging of xenograft tumors using Ir(III) complexes as in vivo intravascular and intracellular probes.

Hypoxia is an important feature of the tumor microenvironment (TME) of most solid tumors, and it is closely linked to cancer cell proliferation, therapy resistance, and the tumor immune response. Herein, we describe a method for hypoxia-induced heterogeneous oxygen distribution in xenograft tumors based on phosphorescence imaging microscopy (PLIM) using intravascular and intracellular oxygen probes. We synthesized Ir(III) complexes with polyethylene glycol (PEG) units of different molecular weights into the ligand as intravascular oxygen probes, BTP-PEGm (m = 2000, 5000, 10000, 20000). BTP-PEGm showed red emission with relatively high emission quantum yield and high oxygen sensitivity in saline. Cellular and in vivo experiments using these complexes revealed that BTP-PEG10000 was the most suitable probe in terms of blood retention and ease of intravenous administration in mice. PLIM measurements of xenograft tumors in mice treated with BTP-PEG10000 allowed simultaneous imaging of the tumor microvasculature and quantification of oxygen partial pressures. From lifetime images using the red-emitting intracellular oxygen probe BTPDM1 and the green-emitting intravascular fluorescent probe FITC-dextran, we demonstrated hypoxic heterogeneity in the TME with a sparse vascular network and showed that the oxygen levels of tumor cells gradually decreased with vascular distance.

Installation of superacidic carbon acid moieties into polymer materials via post-polymerization modification.

In the fields of polymer and material chemistries, strong acid units have mainly included sulfonic acids, which has limited the extension of related material chemistries. Here, a unique carbon acid functionality, namely the bis[(trifluoromethyl)sulfonyl]methyl group, was integrated with polymers via a simple postpolymerization modification with the outstandingly electrophilic 1,1-bis[(trifluoromethyl)sulfonyl]ethylene. The proposed synthesis protocol was verified as an efficient process even for solid-state reactions. The synthesis afforded an organic material with a surface decorated with bis[(trifluoromethyl)sulfonyl]methyl units. The fabricated membranes featuring surface bis[(trifluoromethyl)sulfonyl]methyl units functioned as efficient organocatalysts with high catalytic activity for the Mukaiyama aldol reaction. This study provides a simple method for installing superacidic carbon acid moieties onto the surfaces of materials without tedious chemical treatments.

Controlled positioning of activated ester moieties on well-defined linear polymer chains.

The successful sequence-controlled installation of an activated ester using a newly designed monomer pentafluorophenyl 4-maleimidobenzoate is demonstrated. Pentafluorophenyl 4-maleimidobenzoate is kinetically installed at different stages of a nitroxide-mediated polymerization, namely, near the α-chain end and in the middle of a PS chain. In addition, successful installation of apolar and polar functional groups is achieved via post-polymerization functionalization, which demonstrated the versatility of the synthesis of a universal precursor for locally functionalized polymers.

Surface Engineering of Fluoropolymer Films via the Attachment of Crown Ether Derivatives Based on the Combination of Radiation-Induced Graft Polymerization and the Kabachnik-Fields Reaction.

In this manuscript, we present the successful attachment of crown ether moieties onto fluoropolymer surfaces, via the combination of radiation-induced graft polymerization and a subsequent surface Kabachnik-Fields three-component reaction. The obtained crown ether-tethered fluoropolymer films exhibited an ammonium cation capturing ability, owing to the host-guest interactions (i.e., hydrogen bonding) between the surface-anchored crown ethers and the guest ammonium cations.

Effect of anion in carboxylate-based ionic liquids on catalytic activity of transesterification with vinyl esters and the solubility of cellulose.

The role of 1-ethyl-3-methylimidazolium (Emim) carboxylate-type ionic liquid (IL) as the solvent and organocatalyst for transesterification reaction of cellulose was investigated. The reported method using Emim acetate and vinyl ester caused an undesired side reaction: the acetate anion derived from EmimOAc was introduced into cellulose ester. To improve the reaction system, ILs with a high cellulose solubility, a high degree of substitution (DS) value, and low side-reaction were systematically explored. Newly synthesized Emim p-anisate and a mixed solvent system achieved the transesterification reaction of cellulose with a high DS value derived from the employed vinyl esters (DS > 2.9), and a low DS value derived from side reaction (selectivity > 99%).

Size-specific, colorimetric detection of counteranions by using helical poly(phenylacetylene) conjugated to L-leucine groups through urea acceptors.

A colorimetric detection susceptible to the dimensions of guest counteranions has been demonstrated by using poly(phenylacetylene) with L-leucine and urea functionalities (poly-PA-Leu). Poly-PA-Leu was prepared from N-(4-ethynylphenylcarbamoyl)-L-leucine ethyl ester (PA-Leu) by using [Rh(+){eta(6)-C(6)H(5))B(-)(C(6)H(5))(3)}(2,5-norbornadiene)] as a catalyst. The biased helical conformation of poly-PA-Leu was demonstrated through Cotton effects in the circular dichroism (CD) spectra. The addition of ammonium salts, including tetra-n-butylammonium acetate, tetra-n-butylammonium chloride, and tetra-n-butylammonium bromide anions (CH(3)COO(-), Cl(-), and Br(-)), into the poly-PA-Leu solution intensified the CD responses of poly-PA-Leu, which is indicative of the chiral adjustability of anion recognition by using urea groups. In addition, the combination of poly-PA-Leu with the CH(3)COO(-), Cl(-), and Br(-) anions promoted large redshifts in the absorption spectra, thus providing dramatic color changes from pale yellow to red. Guest dependency in the CD and UV/Vis spectra was clearly correlated with the size of the counteranions. Fundamentally, the addition of tetra-n-butylammonium nitrate, tetra-n-butylammonium hydrogen sulfate, tetra-n-butylammonium perchlorate, tetra-n-butylammonium azide, tetra-n-butylammonium fluoride, and tetra-n-butylammonium iodide anions (NO(3) (-), HSO(4) (-), ClO(4) (-), N(3) (-), F(-), and I(-)) has no effect on either the CD or UV/Vis profiles of poly-PA-Leu. The guest specificity observed in the CD and UV/Vis spectra clearly demonstrated the guest-dimension selectivity of poly-PA-Leu in counteranion recognition.

Cellulose triacetate synthesis via one-pot organocatalytic transesterification and delignification of pretreated bagasse.

Cellulose triacetate was synthesised by the transesterification reaction of mild acid-pretreated lignocellulosic biomass with a stable acetylating reagent (isopropenyl acetate, IPA) in an ionic liquid (1-ethyl-3-methylimidazolium acetate, EmimOAc) which enabled the dissolution of lignocellulose as well as the organocatalytic reaction. The homogeneous acetylation of pretreated sugar-cane bagasse was carried out under mild conditions (80 °C, 30 min), and the subsequent reprecipitation processes led to enriched cellulose triacetate with a high degree of substitution (DS; 2.98) and glucose purity (∼90%) along with production of lignin acetate.

Synthesis of Polymers via Kabachnik-Fields Polycondensation.

Kabachnik-Fields reaction was employed as a new method for polycondensation. For this purpose, polymers were prepared from a mixture of dialdehydes, diamines, and phosphites. Variation of different starting monomers allowed the synthesis of polymers with tunable properties. It not only allowed the variation of glass transition temperatures but also enabled the synthesis of highly functional polymers including zwitterionic polymers. Further, photodegradable polymers have been realized by utilizing a photolabile dialdehyde monomer, which renders the obtained polymers highly interesting for numerous applications.

Ionic liquid/ultrasound pretreatment and in situ enzymatic saccharification of bagasse using biocompatible cholinium ionic liquid.

Choline acetate (ChOAc), a cholinium ionic liquid (IL), showed almost the same bagasse pretreatment capability as 1-ethyl-3-methylimidazolium acetate (EmimOAc), a conventional imidazolium IL used for biomass pretreatment. Moreover, ChOAc showed less of an inhibitory effect on cellulase than EmimOAc. Thus, ChOAc was used for IL/ultrasound-assisted pretreatment and in situ enzymatic saccharification, where IL was not washed out from the pretreated bagasse but diluted with the addition of a buffer solution. When in situ saccharification was performed for 48h in the presence of 10% ChOAc, the cellulose and hemicellulose saccharification percentages were 80% and 72%, respectively. When ChOAc was increased to 20%, the saccharification percentages were 72% and 53%, respectively. However, the values were just 28% and 2%, respectively, in case of 20% EmimOAc. A glucose/xylose solution free from IL and ChOAc aqueous solution without these sugars could be recovered separately by electrodialysis of the hydrolysate of in situ saccharification.

Saccharification and ethanol fermentation from cholinium ionic liquid-pretreated bagasse with a different number of post-pretreatment washings.

Choline acetate (ChOAc), a cholinium ionic liquid (IL), was compared with 1-ethyl-3-methylimidazolium acetate (EmimOAc) with regard to biomass pretreatment, inhibition on cellulase and yeast, residuals in pretreated biomass, and saccharification and fermentation of pretreated biomass. Irrespective of ChOAc and EmimOAc, cellulose and hemicellulose saccharification of the IL-pretreated bagasse were over 90% and 60%, respectively. Median effective concentrations (EC50) based on cellulase activity were 32 wt% and 16 wt% for ChOAc and EmimOAc, respectively. The EC50 based on yeast growth were 3.1 wt% and 0.3 wt% for ChOAc and EmimOAc respectively. The residuals in IL-pretreated bagasse were 10% and 23% for ChOAc and EmimOAc, respectively, when washed 2 times after pretreatment. Ethanol yield on a bagasse basis were 60% and 24% for ChOAc and EmimOAc, respectively, in the saccharification and fermentation of IL-pretreated bagasse when washed 2 times. ChOAc-pretreated bagasse could be saccharified and fermented with fewer wash times than EmimOAc-pretreated bagasse.

Efficient Multicomponent Postpolymerization Modification Based on Kabachnik-Fields Reaction.

A Kabachnik-Fields postpolymerization modification reaction (KF-PMR) was conducted on poly(4-vinyl benzaldehyde) (poly(St-CHO)) with amines and phosphites. Successful KF-PMR was demonstrated by precise structural analysis of the obtained polymers and kinetic investigation of the KF-PMR processes, making it a powerful tool for postpolymerization modifications that lead to α-amino phosphonates as side groups.

Three-Component Reactions for Post-Polymerization Modifications.

A Cu-catalyzed multi-component reaction (CuMCR) of terminal alkynes, sulfonyl azides, and amines was employed in a post-polymerization modification process. The reaction was conducted on polystyrene bearing 20 mol % alkyne groups with 4-toluenesulfonyl azide and dihexylamine in the presence of a Cu(PPh3)3Br/diisopropylethylamine catalyst. The CuMCR on polymer proceeded efficiently, as confirmed by the obvious gas evolution during the reaction, and the conversion of alkyne moiety reached almost 100%, yielding polymeric N-sulfonylamidine derivatives, as proven by 1H NMR measurements. In addition, the precise structural assignment was proven by synthesis and analysis of the model monomeric compound (styrene N-sulfonylamidine) and the respective model polymer. We have successfully demonstrated the utiliztation of this new post-modification reaction by employing various amines including dipeptide and 1-aza-15-crown-5-ether.

Photocleavable Triblock Copolymers Featuring an Activated Ester Middle Block: "One-Step" Synthesis and Application as Locally Reactive Nanoporous Thin Films.

Polystyrene-block-poly(maleimide pentafluorophenyl ester-co-styrene)-block-poly(ethylene oxide) with an o-nitrobenzyl ester junction was synthesized by "one-step" RAFT polymerization. Highly ordered and locally reactive nanoporous thin films were obtained from the photocleavable triblock copolymer after spin coating, solvent annealing, UV exposure, and washing with methanol/water to remove the minor block PEO. The local reactivity in the thin films was demonstrated by fabrication of iron oxide nanotori after post-modification with an amino-functionalized ferrocene and treatment with oxygen plasma.