Treatment in Swelling Solutions Modifying Cellulose Fiber Reactivity – Part 2: Accessibility and Reactivity

The reorganization of cellulose fibers by swelling treatments in alkali solutions results in numerous changes to fiber structure, causing changes of chemical reactivity in the fiber-solution heterogeneous system. An important part of the change in chemical reactivity is the change of fiber accessibility because it results in exclusion of chemicals such as reagents or catalysts from the fiber. In the second of a two-part series of papers, we examine the influence of changes in fiber accessibility and/or reactivity due to treatment in swelling solutions on the performance or behavior of substrates during and after chemical finishing treatments. Changes in fiber accessibility due to alkali treatments are visualized with fluorescence microscopy. The effect of alkali treatments on enzymatic hydrolysis and pad-dry-cure crosslinking treatments of cellulose substrates are discussed as representative examples to demonstrate the effects of swelling processes on fiber reactivity and accessibility. Model calculations indicate that a considerable redistribution of chemicals in substrates occurs during dry-cure operations resulting from molecule-specific exclusion effects. Pilling tests on lyocell knit-fabrics show the impact of preceding alkali processes on the final physical performance of textile fabric highlighting the importance of correct selection of alkali processes to achieve desired behavior.     

Swelling and Dissolution of Cellulose Part 1: Free Floating Cotton and Wood Fibres in N-Methylmorpholine-N-oxide–Water Mixtures

Summary: Five modes describing the behaviour of cellulose fibres dipped in a chemical have been identified:

• Mode 1: Fast dissolution by disintegration into fragments
• Mode 2: Large swelling by ballooning, and dissolution
• Mode 3: Large swelling by ballooning, and no dissolution
• Mode 4: Homogeneous swelling, and no dissolution
• Mode 5: No swelling and no dissolution

In the case of the behaviour of wood and cotton cellulose fibres in N-methylmorpholine-N-oxide (NMMO) and water mixtures, four domains of water content have been identified. Below 17% of water up to monohydrate (13%), the fibres are disintegrated into rod-like fragments and dissolve (mode 1). In NMMO – water mixtures containing 19–24% water, the cellulose fibres exhibit a heterogeneous swelling by forming balloons (composed of dissolved cellulose holds inside a membrane) separated with non-swollen sections. The whole fibre will completely dissolve (mode 2) in four successive steps (growth of the balloons, burst of the balloons, dissolution of the non-swollen sections and finally dissolution of the membrane). With still greater water contents (25–30%), only the ballooning phenomenon is observed, with a partial dissolution inside the balloon (mode 3). Above 35% of water, the fibres swell homogeneously and are not dissolving (mode 4).     

Contributions to Forming and Analytical Investigations of Solutions of Cellulose and Cellulose Derivatives – A Research and Development Topic of the TITK eV

Modification, forming and analytical characterisation of cellulose and cellulose solutions represents one of the most important research topics of the Thuringian Institute for Textiles and Plastics Research (TITK). The presentation provides information on the current capabilities of the institute and on the analytical methods developed in these fields.     

Cellulose solutions in N-methylmorpholine-N-oxide (NMMO) – degradation processes and stabilizers

Efficient stabilization of cellulose solutions in NMMO(1) against side reactions and their harmful effects meansprevention of both homolytic and heterolytic side reactions, which is mainlyaccomplished by trapping radicals, formaldehyde, andN-(methylene)iminium ions (5). Whileradical trapping is commonly reflected by the antioxidativeefficiency, the effectivity against heterolyticdegradationin the Lyocell dope can be expressed by the newly introduced termformaldehyde trapping capacity (FTC). Propyl gallate (PG,4), the most widely applied Lyocell stabilizer nowadays, actsas a phenolic antioxidant, and is finally oxidized to a deeply colored, highlyconjugated chromophore (11) via ellagicacid (10). It was demonstrated that 4 is alsoa quencher of formaldehyde and N-(methylene)iminium ions,both in organic solutions of NMMO and in Lyocell dope. The processes of radicaltrapping and scavenging of HCHO/5 are competitive in the caseof propyl gallate. A novel oxa-chromanol derivative, PBD (14),was designed as stabilizer for Lyocell solutions. In analogy to propyl gallate,PBD acts as a scavenger of all three dangerous species, namely HCHO,5 and radicals. Upon oxidation by radical species, PBDreleasesacetaldehyde which acts as a very efficient HCHO trap. Thus, in contrast topropyl gallate, radical trapping and HCHO trapping are not competitive. Boththeantioxidative efficiency and the capacity to trap HCHO and 5are higher for PBD as compared to propyl gallate. In preliminary stabilizertesting, mixtures of PBD and PG proved to be especially effective.     

Coordination of Heterovalent Iron Atoms in SrCo1 – yFeyO3 – zSolid Solutions

Mössbauer spectroscopy was used to study hyperfine interactions on ⁵⁷Fe nuclei of SrCo_{1 – y} Fe _y O_{3 – z} solid solutions (0.2 y 0.8). The ⁵⁷Fe spectra measured in the paramagnetic temperature range look like a superposition of two quadrupole doublets whose parameters correspond to high-spin Fe⁴⁺cations ( = 0.1 mm/s; = 0.4 mm/s) in the anion surrounding with coordination number 5 (tetragonal pyramid) and to Fe³⁺cations ( = 0.3 mm/s; = 0.4 mm/s) in the distorted octahedral environment. The relative number and pattern of distribution of heterovalent cations (Co⁴⁺, Co³⁺, Fe⁴⁺, and Fe³⁺) in the B-sublattice of perovskites were determined. The values of the electronic exchange constants in the solid solutions obtained through Mössbauer spectroscopy were compared with those obtained from thermodynamic calculations. The oxygen penetration in perovskites was found to depend on their composition and structure.     

Topography and Field Effects in Secondary Ion Mass Spectrometry – Part I: Conducting Samples

Quantitative chemical characterization of surfaces with topography by secondary ion mass spectrometry (SIMS) remains a significant challenge due to the lack of systematic and validated measurement methods. In this study, we combine an experimental approach using a simple model system with computer simulation using SIMION, to understand and quantify the key factors that give rise to unwanted topographic artefacts in SIMS images of conducting samples with microscale topography. Experimental data are acquired for gold wires (diameters 33 to 125 μm) mounted onto silicon wafers. Significant loss of ion intensities and shadowing arise from the distortion of the extraction field, and the chemical analysis over the whole of the sample surface is difficult. For large primary ion incidence angles of ≥55° to the surface normal, a fraction of the primary ions are scattered from the target and impact the substrate, emitting secondary ions that may be mistaken as originating from the wire. For conducting samples, topographic field effects may be reduced by the use of a smaller extraction voltage and an extraction delay. The effects of an extraction delay on ion intensities, mass resolution and time-of-flight are studied, and its application is demonstrated on an anisotropically etched silicon sample. The use of a simple sample holder with a V-shaped groove to reduce topographic field effects for wires is also presented. Using these results, we provide clear guidance to analysts for the diagnosis and identification of topography effects in SIMS, and present key recommendations to minimize them in practical analysis.     

Reactivity of benzylidene and alkylidenemalonates in radical addition mediated with dialkylzincs – An intriguing story

Benzylidene- and alkylidenemalonates are extremely reactive radical acceptors in dialkylzinc-mediated radical additions. Theoretical investigations showed that the multi-step radical-polar crossover process should be highly exothermic. Not only the addition of the alkyl radical to the complexed substrate is enthalpically favored but what is more, the homolytic substitution at the metal leading to a zinc enolate should also be exothermic, even though it necessitates the cleavage of the C-Zn bond from the complexed α-alkoxycarbonyl radical intermediate. This work was undertaken to highlight the power of chelation in controlling the fate of this type of reaction. Much to our surprise, no unambiguous experimental evidence could be put forward to prove the formation of the expected zinc enolate intermediate. Additionally, benzylidenemalonates and their alkylidene analogues (although to a lesser extent) exhibit an intriguing behavior. The backward reaction (retro-addition) can be triggered at work-up depending upon experimental conditions.     

Intrachain and Interchain Interactions in Polystyrene: Dilute andSemidilutc Solutions

Thestudiesofpolymersolutionpropertiesfromdilatetoconcentratedsolutionbyfluorescencetechniquehaveattractedmoreattentionsinrecentdecadesl'2.InordertoinvestigateintrachainandinterchainilltCractionsindilutesolutionregion,pyrenewasusedaslabelsattachedtopolystyrene,whichwasintenselyfluorescentwithalongfluorescentlifetime3.Inthepresentwork,thepolystyreneattachedwithpyrenylgroupshadanunfavourablestrUcturetothenearestneighborexcimerformationwiththepyrenylgroupsseparatedbymorethanthreeatomsalongthechain…     

Re-Emerging Field of Lignocellulosic Fiber – Polymer Composites and Ionizing Radiation Technology in their Formulation

Natural cellulose-based fibers offer low cost, low density composite reinforcement with good strength and stiffness. Because of their annual renewability and biodegradability, natural fibers have materialized as environmentally-friendly alternatives to synthetic fibers in the last two decades. They are replacing synthetic materials in some traditional composites in industrial manufacturing sectors such as automotive, construction, furniture, and other consumer goods. In this work, the use of lignocellulosic fibers in green materials engineering, particularly their application as polymeric composite reinforcement and surface treatment via ionizing radiation are reviewed. Because these cellulose-based materials are intrinsically hydrophilic, they require surface modification to improve their affinity for hydrophobic polymeric matrices, which enhances the strength, durability, and service lifetime of the resulting lignocellulosic fiber-polymer composites. In spite of a long history of using chemical methods in the modification of material surfaces, including the surface of lignocellulosic fibers, recent research leans instead towards application of ionizing radiation. Ionizing radiation methods are considered superior to chemical methods, as they are viewed as clean, energy saving, and environmentally friendly. Recent applications of controlled ionizing radiation doses in the formulation of natural fiber –reinforced polymeric composites resulted in products with enhanced fiber-polymer interfacial bonding without affecting the inner structure of lignocellulosic fibers. These applications are critically reviewed in this contribution.     

Reactive Extraction of Citric Acid Using Tri-n-octylamine in Nontoxic Natural Diluents: Part 1—Equilibrium Studies from Aqueous Solutions

Use of cheap, nontoxic, and selective solvents could economically provide a solution to the recovery of carboxylic acids produced by the bioroute. In this regard in the present paper, reactive extraction of citric acid was studied. Problems encompassing the recovery of the acid ([H₃A] _aq ^o ?=?0.1?C0.8) was solved by using tertiary amine (tri-n-octylamine, TOA) in natural diluents (rice bran oil, sunflower oil, soybean oil, and sesame oil). TOA was very effective in removal of acid providing distribution coefficient (D) as high as 18.51 (E%?=?95?%), 12.82 (E%?=?93?%), 15.09 (E%?=?94?%), and 16.28 (E%?=?94?%) when used with rice bran oil, sunflower oil, soybean oil, and sesame oil, respectively. Overall extraction constants and association numbers for TOA + rice bran oil, TOA + sunflower oil, TOA + soybean oil, and TOA + sesame oil were evaluated to be 35.48 (mol/l)^?1.46, 29.79 (mol/l)^?1.30, 33.79 (mol/l)^?1.51, and 37.64 (mol/l)^?1.65 and 1.46, 1.30, 1.51, and 1.65, respectively. Specific equilibrium complexation constants (K _E(n/m)) were also predicted using mathematical modeling.     

Mannose‐BSA Conjugates: Comparison Between Commercially Available Linkers in Reactivity and Bioactivity

Mannosyl ethanolamine and BSA were conjugated together by their amino groups with various homobifunctional cross‐linker reagents: disuccinimidyl carbonate (DSC), disuccinimidyl glutarate (DSG), disuccinimidyl suberate (DSS), ethylene glycolbis(succinimidylsuccinate) (EGS), 1,5‐difluoro‐2,4‐dinitrobenzene (DFDNB), diethyl squarate (DES), and thiophosgene (TP). The resulting mannose-BSA conjugates were subjected to an enzyme‐linked lectin assay (ELLA)to investigate their affinity to concanvalin A (ConA). With these results, the seven linkers were evaluated on the basis of five criteria, i.e., cost, reactivity, sugar loading, homogeneity, and affinity to ConA. Thus, DSS, DFDNB, and DES seemed to have advantages over the other cross-linking reagents.     

BaTi1−x SnxO3 Solid Solutions: Solid-Phase and Sol-Gel Syntheses and Characterization

Ba(Ti_1?x Sn_x)O₃ solid solutions were synthesized by the sol-gel process and solid-phase reactions, and their electrophysical properties studied. SnCl₄ · 5H₂O, TiCl₄, and BaCO₃ were precursors in the sol-gel process. IR spectroscopy, X-ray powder diffraction, and differential thermal analysis were used to study the formation conditions for BaTiO₃, BaSnO₃, and BaTi_0.85Sn_0.15O₃.     

Molecular Motions and Interactions in Aqueous Solutions of Thymosin-β4, Stabilin CTD and Their 1 : 1 Complex,Studied by 1H-NMR Spectroscopy

Wide-line ¹H NMR measurements were extended and all results were interpreted in a thermodynamics-based new approach on aqueous solutions of thymosin-β₄ (Tβ₄), stabilin cytoplasmic domain (CTD), and their 1 : 1 complex. Energy distributions of potential barriers controlling the motion of protein-bound water molecules were determined. Heterogeneous and homogeneous regions were found in the protein-water interface. The measure of heterogeneity of this interface gives quantitative value for the portion of disordered parts in the protein. Ordered structural elements were found extending up to ∼20 % of the individual whole proteins. About 40 % of the binding sites of free Tβ₄ get involved in bonds holding the complex together. The complex has the most heterogeneous solvent accessible surface (SAS) in terms of protein-water interactions. The complex is more disordered than Tβ₄ or stabilin CTD. The greater SAS area of the complex is interpreted as a clear sign of its open structure.     

Thermo-mechanical characterisation of in-plane properties for CSM E-glass epoxy polymer composite materials – Part 1: Thermal and chemical strain

The in-plane thermo-mechanical properties and residual stresses of a CSM E-glass/Epoxy material are characterised through the use of DSC and TMA. The measured data is used to generate material models which describe the mechanical behaviour as a function of conversion and temperature. The in-plane thermal expansion coefficient (α) of the composite material decreases above the glass transition temperature (T_g), which is compensated by a higher out of plane deformation above T_g. Comparison of α and chemical shrinkage measurements suggests that chemical bonds between the polymer matrix and the glass fibres are formed prior to shrinkage of the epoxy matrix, i.e., at an early processing stage. This suggests that production of composites with low residual stresses requires focus on reactivity between the matrix and the sizing rather than the matrix cure properties. As a consequence, residual stresses in the composite material are mainly a result of restricted cure shrinkage rather than mismatch between thermal expansion coefficients.     

Structure and stability of halogenated polymers: Part 1—Ring-chlorinated polystyrene

Ring-chlorinated polystyrene has been prepared by reaction between polymer and chlorine at −20°C in the presence of iodine, using a 1·2:1 molar ratio of chlorine to styrene units. Although the product has a composition corresponding precisely to 1 Cl atom per styrene unit and the predominant site of chlorination is the para position in the aromatic ring, some ortho chlorination, backbone chlorination and unchlorinated structures have been shown to be present by characterisation spectroscopically and from degradation experiments.The chlorinated polymer loses the backbone chlorine readily as HCl at temperatures from 200°C. The resulting unsaturation in the backbone appears to destabilise the polymer towards chain scission and the main breakdown process, which resembles that of polystyrene in consisting of depolymerisation and transfer reactions, occurs over a wider temperature range and at lower temperatures than the decomposition of polystyrene. Products have been identified and estimated quantitatively.     

The Use of Bone Substitutes in the Treatment of Bone Defects – the Clinical View and History

Summary: Bone has the ability to regenerate and remodel itself. In the clinic circumstances appear when bone defects do not heal spontaneously. These situations frequently result from trauma, congenital abnormities, infection or tumor resection. Hence, filling of the resulting defect by bone transplantation is a common practise with an increasing value in the re-establishment of the musculoskeletal system to promote bone healing. Since decades, efforts have been put to improve the effectiveness of bone substitutes. Conventional approaches with the use of ivory, animal and also human bone were not satisfactory. Negative effects like allergic reactions, rejection reactions, inflammations and other problems occurred. These led to implant failure, non union and amputation, to only mention a few. The introduction of bone banks and the development of standards in bone transplantation brought up the false hope to find a final solution for the treatment of bone loss. Disease transmissions (HIV) by allografts caused critical discussions. Despite all efforts, transplantation of autogenous cancellous bone is still the “gold standard” to induce bone healing. However, autografts are only limited available and are accompanied with high morbidity and mortality during the harvest. The problems associated with autologous and allogenous bone grafts promoted the development of multiple organic and inorganic bone substitutes. Well established substitutes at the present are demineralised bone matrix (DBM), composites and calcium phosphates (hydroxyl apatite and tri-calcium phosphate). These osteoconductive substances have shown to improve new bone formation. Nevertheless, clinical application of these materials is merely successful in a good bony environment but does not induce large progress in critical bone defects.     

Solutions of ionic liquids with diverse aliphatic and aromatic solutes – Phase behavior and potentials for applications: A review article

This article principally reviews our research related to liquid–liquid and solid–liquid phase behavior of imidazolium- and phosphonium-based ionic liquids, mainly having bistriflamide ([NTf₂]⁻) or triflate ([OTf]⁻) anions, with several aliphatic and aromatic solutes (target molecules). The latter include: (i) diols and triols: 1,2-propanediol, 1,3-propanediol and glycerol; (ii) polymer poly(ethylene glycol) (PEG): average molecular mass 200, 400 and 2050 – PEG200 (liquid), PEG400 (liquid) and PEG2050 (solid), respectively; (iii) polar aromatic compounds: nicotine, aniline, phenolic acids (vanillic, ferulic and caffeic acid,), thymol and caffeine and (iv) non-polar aromatic compounds (benzene, toluene, p-xylene). In these studies, the effects of the cation and anion, cation alkyl chain and PEG chain lengths on the observed phase behaviors were scrutinized. Thus, one of the major observations is that the anion – bistriflamide/triflate – selection usually had strong, sometimes really remarkable effects on the solvent abilities of the studied ionic liquids. Namely, in the case of the hydrogen-bonding solutes, the ionic liquids with the triflate anion generally exhibited substantially higher solubility than those having the bistriflamide anion. Nevertheless, with the aromatic compounds the situation was the opposite – in most of the cases it was the bistriflamide anion that favoured solubility. Moreover, our other studies confirmed the ability of PEG to dissolve both polar and non-polar aromatic compounds. Therefore, two general possibilities of application of alternative, environmentally acceptable, solvents of tuneable solvent properties appeared. One is to use homogeneous mixtures of two ionic liquids having [NTf₂]⁻ and [OTf]⁻ anions as mixed solvents. The other, however, envisages the application of homogeneous and heterogeneous (PEG + ionic liquid) solutions as tuneable solvents for aromatic solutes.Such mixed solvents have potential applications in separation of the aforesaid target molecules from their aqueous solutions or in extraction from original matrices. From the fundamental point of view the phase equilibrium studies reviewed herein and the diversity of the pure compounds – ionic liquids and target molecules – represent a good base for the discussion of interactions between the molecules that exist in the studied solutions.     

Sorption of organic liquids in poly(ethylene chlorotrifluoroethylene) Halar®901: Experimental and theoretical analysis

Sorption of liquids in polymers is an important factor for any application where polymers come into contact with an organic solvent. We report on sorption properties of hydrophobic poly(ethylene chlorotrifluoroethylene) Halar^®901 in view of its potential application as a membrane material. For the first time, the liquid phase sorption of 34 common organic liquids such as linear C₆C₁₀ alkanes, methyl-, ethyl- and propyl-derivates of benzene and cyclohexane and of linear-, branched- and cyclic-ethers, ketones, acetates and chloroderivates in the 1:1 alternating copolymer of ethylene and chlorotrifluoroethylene (ECTFE) is presented. The effects of solvent molecular structure and its physico-chemical properties on the total mass uptake are discussed in detail. Furthermore, two sorption-predictive methods developed from determined data allows to anticipate the behavior of solvents in Halar^®901 based exclusively on three type of structural units (C-bone, functional groups, molecular geometry) or four (molar mass, surface tension, boiling temperature and Van der Waals volume) parameters only. A successful verification of our methods proved their versatility in predicting organic liquid sorption in ECTFE material Halar^®901.     

Are Clusters Important in Understanding the Mechanisms in Atmospheric Pressure Ionization? Part 1: Reagent Ion Generation and Chemical Control of Ion Populations

It is well documented since the early days of the development of atmospheric pressure ionization methods, which operate in the gas phase, that cluster ions are ubiquitous. This holds true for atmospheric pressure chemical ionization, as well as for more recent techniques, such as atmospheric pressure photoionization, direct analysis in real time, and many more. In fact, it is well established that cluster ions are the primary carriers of the net charge generated. Nevertheless, cluster ion chemistry has only been sporadically included in the numerous proposed ionization mechanisms leading to charged target analytes, which are often protonated molecules. This paper series, consisting of two parts, attempts to highlight the role of cluster ion chemistry with regard to the generation of analyte ions. In addition, the impact of the changing reaction matrix and the non-thermal collisions of ions en route from the atmospheric pressure ion source to the high vacuum analyzer region are discussed. This work addresses such issues as extent of protonation versus deuteration, the extent of analyte fragmentation, as well as highly variable ionization efficiencies, among others. In Part 1, the nature of the reagent ion generation is examined, as well as the extent of thermodynamic versus kinetic control of the resulting ion population entering the analyzer region.