Synthesis of Fluoropolymers in Supercritical Carbon Dioxide

Hierarchically porous materials: synthesis strategies and structure design

This review addresses recent advances in synthesis strategies of hierarchically porous materials and their structural design from micro-, meso- to macro-length scale.

Microcosmic understanding on thickening capability of copolymers in supercritical carbon dioxide: the key role of π–π stacking

Thickening capability evaluations and microscopic understanding of St–HFDA copolymers in SC-CO₂.

Organic Polymer Chemistry in the Context of Novel Processes

This article was written to shed light on a series of what some have stated are not so obvious connections that link polymer synthesis in supercritical CO₂ to cancer treatment and vaccines, nonflammable polymer electrolytes for lithium ion batteries, and 3D printing. In telling this story, we also attempt to show the value of versatility in applying one's primary area of expertise to address pertinent questions in science and in society. In this Outlook, we attempted to identify key factors to enable a versatile and nimble research effort to take shape in an effort to influence diverse fields and have a tangible impact in the private sector through the translation of discoveries into the marketplace.

Solvation of Esters and Ketones in Supercritical CO2

Vibrational Raman spectra for the C═O stretching modes of three esters with different functional groups (methyl, a single phenyl, and two phenyl groups) were measured in supercritical carbon dioxide (scCO2). The results were compared with Raman spectra for three ketones involving the same functional groups, measured at the same thermodynamic states in scCO2. The peak frequencies of the Raman spectra of these six solute molecules were analyzed by decomposition into the attractive and repulsive energy components, based on the perturbed hard-sphere theory. For all solute molecules, the attractive energy is greater than the repulsive energy. In particular, a significant difference in the attractive energies of the ester-CO2 and ketone-CO2 systems was observed when the methyl group is attached to the ester or ketone. This difference was significantly reduced in the solute systems with a single phenyl group and was completely absent in those with two phenyl groups. The optimized structures among the solutes and CO2 molecules based on quantum chemical calculations indicate that greater attractive energy is obtained for a system where the oxygen atom of the ester is solvated by CO2 molecules.

Driving Forces Controlling Host-Guest Recognition in Supercritical Carbon Dioxide Solvent

The formation of supramolecular host-guest complexes is a very useful and widely employed tool in chemistry. However, supramolecular chemistry in non-conventional solvents such as supercritical carbon dioxide (scCO2 ), one of the most promising sustainable solvents, is still in its infancy. In this work, we explored a successful route to the development of green processes in supercritical CO2 by combining a theoretical approach with experiments. We were able to synthesize and characterize an inclusion complex between a polar aromatic molecule (benzoic acid) and peracetylated-β-cyclodextrin, which is soluble in the supercritical medium. This finding opens the way to wide, environmental friendly, applications of scCO2 in many areas of chemistry, including supramolecular synthesis, reactivity and catalysis, micro and nano-particle formation, molecular recognition, as well as enhanced extraction processes with increased selectivity.

Ultra-low dielectric constant materials with hydrophobic property derived from polyhedral oligomeric silsequioxane (POSS) and perfluoro-aromatics

Soluble poly(arylene ether)s with perfluoro-aromatics and POSS in the main chains exhibited ultra low dielectric constants and hydrophobic properties.

Block copolymer synthesis by controlled/living radical polymerisation in heterogeneous systems

We review the range of CLRP-controlled syntheses of block copolymer particles in dispersed systems, which are being exploited to create new opportunities for the design of nanostructured soft materials.

Complexes of carbon dioxide with dihalogenated ethylenes: structure, stability and interaction

Interactions of ethylene and its 1,2-dihalogenated derivatives with CO₂ induce twenty four molecular complexes with stabilization energies in the range of 1.1 to 7.5 kJ mol⁻¹ as computed at the CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVDZ level of theory.

Selected physicochemical aspects of poly- and perfluoroalkylated substances relevant to performance, environment and sustainability-part one

The elemental characteristics of the fluorine atom tell us that replacing an alkyl chain by a perfluoroalkyl or polyfluorinated chain in a molecule or polymer is consequential. A brief reminder about perfluoroalkyl chains, fluorocarbons and fluorosurfactants is provided. The outstanding, otherwise unattainable physicochemical properties and combinations thereof of poly and perfluoroalkyl substances (PFASs) are outlined, including extreme hydrophobic and lipophobic character; thermal and chemical stability in extreme conditions; remarkable aptitude to self-assemble into sturdy thin repellent protecting films; unique spreading, dispersing, emulsifying, anti-adhesive and levelling, dielectric, piezoelectric and optical properties, leading to numerous industrial and technical uses and consumer products. It was eventually discovered, however, that PFASs with seven or more carbon-long perfluoroalkyl chains had disseminated in air, water, soil and biota worldwide, are persistent in the environment and bioaccumulative in animals and humans, raising serious health and environmental concerns. Further use of long-chain PFASs is environmentally not sustainable. Most leading manufacturers have turned to shorter four to six carbon perfluoroalkyl chain products that are not considered bioaccumulative. However, many of the key performances of PFASs decrease sharply when fluorinated chains become shorter. Fluorosurfactants become less effective and less efficient, provide lesser barrier film stability, etc. On the other hand, they remain as persistent in the environment as their longer chain homologues. Surprisingly little data (with considerable discrepancies) is accessible on the physicochemical properties of the PFASs under examination, a situation that requires consideration and rectification. Such data are needed for understanding the environmental and in vivo behaviour of PFASs. They should help determine which, for which uses, and to what extent, PFASs are environmentally sustainable.

Crystal phase transformation of α into β phase poly(vinylidene fluoride) via particle formation caused by rapid expansion of supercritical solutions

RESS enables the transformation from α to β phase PVDF. Piezoresponse force microscopy confirmed the piezoelectricity of the obtained particles.

C–H activation dependent Pd-catalyzed carbonylative coupling of (hetero)aryl bromides and polyfluoroarenes

The first intermolecular Pd-catalyzed carbonylative coupling of aryl bromides relying on C–H activation is presented.

Accelerating electrostatic pair methods on graphical processing units to study molecules in supercritical carbon dioxide

Traditionally, electrostatic interactions are modelled using Ewald techniques, which provide a good approximation, but are poorly suited to GPU architectures. We use the GPU versions of the LAMMPS MD package to implement and assess the Wolf summation method. We compute transport and structural properties of pure carbon dioxide and mixtures of carbon dioxide with either methane or difluoromethane. The diffusion of pure carbon dioxide is indistinguishable when using the Wolf summation method instead of PPPM on GPUs. The optimum value of the potential damping parameter, α, is 0.075. We observe a decrease in accuracy when the system polarity increases, yet the method is robust for mildly polar systems. We anticipate the method can be used for a number of techniques, and applied to a variety of systems. Substitution of PPPM can yield a two-fold decrease in the wall-clock time.

Supercritical carbon dioxide: a solvent like no other

Supercritical carbon dioxide (scCO2) could be one aspect of a significant and necessary movement towards green chemistry, being a potential replacement for volatile organic compounds (VOCs). Unfortunately, carbon dioxide has a notoriously poor solubilising power and is famously difficult to handle. This review examines attempts and breakthroughs in enhancing the physicochemical properties of carbon dioxide, focusing primarily on factors that impact solubility of polar and ionic species and attempts to enhance scCO2 viscosity.

Ab initio analysis on the interaction of CO2 binding to peracetated D-glucopyranose

CO2-philes can be utilized as additives, surfactants, and a potential phase-change physical solvent or absorbent for CO2, so the design and synthesis of CO2-philes typically non-fluorous compounds is important to develop more application areas of CO2. Researchers have recently reported that peracetated D-glucopyranose has high solubility in CO2. In order to study the interaction properties between sugar acetates with CO2, 1,2-di-O-acetyl-α-D-glucopyranose and 1,2-di-O-acetyl-β-D-glucopyranose were decided as substrates after initial chemical stimulations with peracetated D-glucopyranose, and the complex model was one CO2 molecule combined with one sugar substrate (1:1). Ab initio calculations of these two systems were accomplished including geometry optimizations with HF/3-21G, B3LYP/6-31+G**, and single point energies calibration with MP2/aug-cc-pVDZ. The results indicated that hydrogen atoms can interact with CO2 by C-H··O hydrogen bond, but the dominant ones are the interactions of oxygen atoms in substrates with a CO2 molecule. It was also found that the binding energies increased when more oxygen atoms of substrate interacted with CO2, but were not affected by their chemical environment. The interaction of sugar substrate with CO2 is distance related, and should be an electrostatic interaction not only Lewis acid-Lewis base and hydrogen bond interactions. Therefore, it can be expected that one CO2-phile could interact with more CO2 molecules if more acetate-like groups or oxygen atoms were introduced into the molecular structure based on all these results, and this can be a guideline for design CO2-philes.

On the ionizing properties of supercritical carbon dioxide: uncatalyzed electrophilic bromination of aromatics

scCO₂, a non-polar solvent with a dielectric constant lower than n-pentane, promotes the electrophilic bromination of aromatics as efficiently as strongly ionizing solvents such as aqueous acetic and trifluoroacetic acids.