Formation and structure of ionomer complexes from grafted polyelectrolytes

We discuss the structure and formation of Ionomer Complexes formed upon mixing a grafted block copolymer (poly(acrylic acid)-b-poly(acrylate methoxy poly(ethylene oxide)), PAA21-b-PAPEO14) with a linear polyelectrolyte (poly(N-methyl 2-vinyl pyridinium iodide), P2MVPI), called grafted block ionomer complexes (GBICs), and a chemically identical grafted copolymer (poly(acrylic acid)-co-poly(acrylate methoxy poly(ethylene oxide)), PAA28-co-PAPEO22) with a linear polyelectrolyte, called grafted ionomer complexes (GICs). Light scattering measurements show that GBICs are much bigger (~70–100 nm) and GICs are much smaller or comparable in size (6–22 nm) to regular complex coacervate core micelles (C3Ms). The mechanism of GICs formation is different from the formation of regular C3Ms and GBICs, and their size depends on the length of the homopolyelectrolyte. The sizes of GBICs and GICs slightly decrease with temperature increasing from 20 to 65 °C. This effect is stronger for GBICs than for GICs, is reversible for GICs and GBIC-PAPEO14/P2MVPI228, and shows some hysteresis for GBIC-PAPEO14/P2MVPI43. Self-consistent field (SCF) calculations for assembly of a grafted block copolymer (having clearly separated charged and grafted blocks) with an oppositely charged linear polyelectrolyte of length comparable to the charged copolymer block predict formation of relatively small spherical micelles (~6 nm), with a composition close to complete charge neutralization. The formation of micellar assemblies is suppressed if charged and grafted monomers are evenly distributed along the backbone, i.e., in case of a grafted copolymer. The very large difference between the sizes found experimentally for GBICs and the sizes predicted from SCF calculations supports the view that there is some secondary association mechanism. A possible mechanism is discussed

Global patient outcomes after elective surgery: prospective cohort study in 27 low-, middle- and high-income countries.

BACKGROUND: As global initiatives increase patient access to surgical treatments, there remains a need to understand the adverse effects of surgery and define appropriate levels of perioperative care. METHODS: We designed a prospective international 7-day cohort study of outcomes following elective adult inpatient surgery in 27 countries. The primary outcome was in-hospital complications. Secondary outcomes were death following a complication (failure to rescue) and death in hospital. Process measures were admission to critical care immediately after surgery or to treat a complication and duration of hospital stay. A single definition of critical care was used for all countries. RESULTS: A total of 474 hospitals in 19 high-, 7 middle- and 1 low-income country were included in the primary analysis. Data included 44 814 patients with a median hospital stay of 4 (range 2-7) days. A total of 7508 patients (16.8%) developed one or more postoperative complication and 207 died (0.5%). The overall mortality among patients who developed complications was 2.8%. Mortality following complications ranged from 2.4% for pulmonary embolism to 43.9% for cardiac arrest. A total of 4360 (9.7%) patients were admitted to a critical care unit as routine immediately after surgery, of whom 2198 (50.4%) developed a complication, with 105 (2.4%) deaths. A total of 1233 patients (16.4%) were admitted to a critical care unit to treat complications, with 119 (9.7%) deaths. Despite lower baseline risk, outcomes were similar in low- and middle-income compared with high-income countries. CONCLUSIONS: Poor patient outcomes are common after inpatient surgery. Global initiatives to increase access to surgical treatments should also address the need for safe perioperative care. STUDY REGISTRATION: ISRCTN5181700

Solvent developments for liquid-liquid extraction of carboxylic acids in perspective

The growing desire to produce organic acids through fermentative routes, as a starting point for bio-based plastics, has revived the scientific attention on carboxylic acid removal from aqueous streams. One of the main technologies to recover carboxylic acids from diluted aqueous streams is liquid-liquid extraction (LLX). In this review, solvent developments for LLX of carboxylic acids are reviewed. In the past decades, a significant number of research papers have appeared, describing completely new solvents such as ionic liquids, as well as improvements of the traditional state-of-the-art solvent systems comprising of amines and organophosphorous extractants in diluents. The state-of-the-art technology for acid extractions has long been using trioctylamine (TOA) — or Alamine 336, a commercial mixture of trialkyl amines — as the complexating agent. However, with dropping acid concentrations, the economic feasibility of the TOA-based processes is compromised. This review discusses three main categories of solvents, i.e. composite solvents containing nitrogen-based extractants, phosphorous-based extractants and ionic liquids, and includes a discussion on solvent property models that may aid solvent selection. Furthermore, regeneration strategies are discussed, aiming to provide direction towards regenerations that do not further dilute streams that are already diluted before the LLX process. The main conclusion with respect to solvent regeneration when back-extraction is applied, is that solvent-swing strategies should be applied that maximize the ratio between the acid distribution coefficient in the forward extraction and the distribution coefficient in the back-extraction at minimal energy cost. This appears to be through evaporation of part of the diluent after the primary extraction

Synthesis and characterization of PY2- and TPA-appended diphenylglycoluril receptors and their bis-Cu-I complexes

Contains fulltext : 35327.pdf (postprint version ) (Open Access

Vapor–liquid behavior of phenol and cumene in ternary and quaternary mixtures

BACKGROUND: Although phenol is a key intermediate in the plastics and polycarbonate industry, it is also a toxic component that requires removal from dilute aqueous streams, potentially by liquid–liquid extraction (LLX). For LLX, cumene is suggested as a solvent as it is already present in processes in the polycarbonate industry. For the recovery of cumene from phenol by distillation, knowledge on vapor–liquid equilibrium (VLE) behavior is important, in combination with how this is affected by other components possibly present as an impurity or explicitly added as a solvent. This was investigated in this work. RESULTS: The binary cumene–phenol system shows a tangent pinch in the binary VLE diagram. Addition of a range of impurities and solvents showed that hydrogen bond accepting compounds strongly improve the relative volatility of the mixture, whereas dodecane, not capable of forming hydrogen bonds, has a negative effect on the relative volatility. CONCLUSION: Addition of polar components with hydrogen bonding abilities, i.e. ketones or ethers, affected the relative volatility of cumene over phenol the most positively. Combining two types of components results in similar effects, and clear synergistic effects could not be shown based on current VLE measurements. Addition of an apolar component in combination with polar components with hydrogen abilities had only a minor effect on the relative volatility

Dynamical heterogeneities and defects in two-dimensional soft colloidal crystals

In this paper we study a two-dimensional system of charged colloidal particles using Brownian dynamics simulations. We determine the phase diagram and investigate the dynamics of this system in the density regime where hexatic and solid phases are stable. We find that the dynamics in these phases is heterogeneous by means of the spontaneous formation and diffusion of highly mobile defects. We identify two key mechanisms associated with the areas of high mobility. The first mechanism involves the highly cooperative motion of a closed loop of particles which shift coherently along the loop until each particle has replaced the position of its predecessor in the chain. The second mechanism involves the spontaneous creation of vacancy-interstitial pairs which diffuse within the hexatic and solid phases. We further explore quantitatively the properties of the open-ended and closed rearrangement strings and find that in the crystal phase the string-size distribution can be approximately matched with a simple, random walk description of vacancies and interstitials on a lattice

Swing processes for solvent regeneration in liquid-liquid extraction of succinic acid

Solvent regeneration processes for liquid-liquid extraction of succinic acid (HSuc) from aqueous streams were investigated. Tri-n-octyl amine (TOA) and tri-n-octyl phosphine oxide (TOPO) in methyl isobutyl ketone (MIBK) showed good extraction. For 20 wt% TOA in MIBK, addition of pentane at anti-solvent-to-solvent ratio of 1 (vol/vol) decreased KD from 10.2 to 0.46, applying ethane at 30 bar decreased KD to 0.45 and increasing the temperature to 60 °C decreased KD to 1.6. Evaporation of MIBK from a solvent of 40 wt% TOA in MIBK decreased KD from 10.2 to 4.0. For these processes, capital investments and energy requirements were calculated for 10 kiloton per year at a concentration factor of 5. Costs of all processes to obtain the product at maximum solubility are less than evaporation (2600 kJ/kg product at maximum solubility). A combination of a swing in diluent and temperature results in higher product concentrations after back-extraction, and reduced the energy input to obtain the pure HSuc to 19 MJ/kg. The ethane-based process is most effective with 13 MJ/kg to obtain the pure HSuc product. Although additional capital investments for compressors and pumps are required, only 110 days of production are required for return on investments