Ester-based surfactants: Are they stable enough?

Surfactants with an ester bond connecting the polar headgroup and the hydrophobic tail are common. They are easy to synthesize, they can often be made from natural raw materials and their biodegradation profile is generally good, partly due to lipase or esterase catalyzed breakdown of the ester bond in sewage plants. A labile ester bond in the molecule may cause problems, however. Surfactants are often formulated at relatively high pH and it is important that they remain intact for a given period of time. In this article we discuss alkaline hydrolysis of different types of ester-based surfactants—cationic, anionic and nonionic—and also of surfactant mixtures. We show that the ester bond in a surfactant has a different hydrolysis pattern than ester bonds in non-surface active uncharged molecules. Cationic ester-based surfactants are hydrolyzed rapidly while anionic and also nonionic ester-containing surfactants are relatively resistant to hydrolysis

Parameters influencing hydrophobization of paper by surface sizing

Paper surface hydrophobization, also referred to as "surface sizing", is often necessary for printing and packaging purposes. Typically, hydrophobic polymeric nanoparticles, in combination with starch are applied on the paper surface at the dry-end of the paper machine. In the surface sizing process, the nature of the nanoparticles, starch type, starch concentration and ratio between starch and nanoparticles, paper quality, ionic strength, and application as well as drying temperature are parameters that influence the result. The aim of this work was to systematically evaluate these parameters in order to create knowledge to be used for optimization of the process. Laboratory scale surface sizing trials were performed and the results from the trials showed that cationic particles gave superior performance compared to anionic particles. Both the starch type and the concentration of the oxidized starch had an impact on the performance. The effect of the ionic strength was found to depend on the particle charge: for cationic particles, the addition of salt was detrimental while for the anionic particles it was beneficial. An increase of the application or the drying temperature was found to enhance the performance up to a temperature around the glass transition temperature of the polymer

Formation and relaxation kinetics of starch-particle complexes

© The Royal Society of Chemistry.The formation and relaxation kinetics of starch-particle complexes were investigated in this study. The combination of cationic nanoparticles in suspension and anionic starch in solution gave rise to aggregate formation which was studied by dynamic light scattering, revealing the initial adsorption of the starch molecules on the particle surface. By examining the stability ratio, W, it was found that even in the most destabilized state, i.e. at charge neutralization, the starch chains had induced steric stabilization to the system. At higher particle and starch concentrations relaxation of the aggregates could be seen, as monitored by a decrease in turbidity with time. This relaxation was evaluated by fitting the data to the Kohlrausch-Williams-Watts function. It was found that irrespective of the starch to particle charge ratio the relaxation time was similar. Moreover, a molecular weight dependence on the relaxation time was found, as well as a more pronounced initial aggregated state for the higher molecular weight starch. This initial aggregate state could be due to bridging flocculation. With time, as the starch chains have relaxed into a final conformation on the particle surface, bridging will be less important and is gradually replaced by patches that will cause patchwise flocculation. After an equilibration time no molecular weight dependence on aggregation could be seen, which confirms the patchwise flocculation mechanism

Accelerated ageing of cotton canvas as a model for further consolidation practices

In order to assess the effectiveness of various practices for canvas consolidation, model substrates areneeded. In this work, a method of rapid ageing of cotton canvas is described. The method consists oftreatment of the canvas with a mixture of hydrogen peroxide and sulfuric acid at 40◦C during 72 hoursto mimic to some extent the natural processes of oxidation and acid-catalysed hydrolysis of cellulose.Two protocols for canvas degradation were developed, which reduced the degree of polymerization ofcellulose from ca. 6250 to ca. 1350 and 450. The reduction of the mechanical properties and the increaseof the negative charge were also quantified. These samples were compared with a canvas degraded usinga state-of-the-art method that takes up to 20 days. The results show that the developed method canprovide a rapid procedure for preparing small samples for testing various consolidation strategies byconservators

An analytical approach to elucidate the architecture of polyethyleneimines

Polyethyleneimine (PEI) is a common polymer used in many industrial applications and in research, especially in surface chemistry. It is available in a wide range of molecular weights and different degrees of branching. It is classified as linear or branched and sometimes the term hyperbranched is also used. This description, however, is quite rough, which limits the possibility to correlate the structure of the PEI to its properties. The aim of this study is to provide analytical tools to characterize the polymer at a level of detail not normally provided by the supplier of PEI. To this end, five commercially available polyethyleneimines were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and nuclear magnetic resonance spectroscopy to gain insight into the structure and the functional groups present in the polymers. Quantitative 13C NMR analysis turned out to be particularly useful, revealing the degree of branching of the polymer based on the ratio of primary, secondary, and tertiary amino groups

pH-Controlled assembly of polyelectrolyte layers on silica nanoparticles in concentrated suspension

Hypothesis: Preparation of suspensions of nanoparticles (>1 wt%) coated with a polyelectrolyte multilayers is a challenging task because of the risk of flocculation when a polyelectrolyte is added to a suspension of oppositely charged nanoparticles. This situation can be avoided if the charge density of the polymers and particles is controlled during mixing so as to separate mixing and adsorption events. Experiments: The cationic polyethylenimine (PEI) and the anionic carboxymethylcellulose (CMC) were used as weak polyelectrolytes. Polyelectrolyte multilayers build-up was conducted by reducing the charge of one of the components during the addition of the next component. Charge density was controlled by tuning pH. Analysis of the suspension of coated nanoparticles was done by means of dynamic light scattering, electrophoresis and small angle x-ray scattering measurements, while quartz crystal microbalance was used to study the build-up process on flat silica surfaces. Findings: Charge density, controlled through pH, can be used as a tool to avoid flocculation during layer-by-layer deposition of polyelectrolytes on 20 nm silica particles at high concentration (∼40 wt%). When added to silica at pH 3, PEI did not induce flocculation. Adsorption was triggered by raising the pH to 11, pH at which CMC could be added. The pH was then lowered to 3. The process was repeated, and up to five polyelectrolyte layers were deposited on concentrated silica nanoparticles while inducing minimal aggregation

Influence of Surfactants on Lipase Fat Digestion in a Model Gastro-intestinal System

In the present study, we use a model gastro-intestinal system to study the influence of different food-grade surface-active molecules (Sn-2 monopalmitin, β-lactoglobulin, or lysophosphatodylcholine) on lipase activity. The interfacial activity of lipase and surfactants are assessed with the pendant drop technique, a commonly used tensiometry instrument. A mathematical model is adopted which enables quantitative determination of the composition of the water–oil interface as a function of bulk surfactant concentration in the water–oil mixtures. Our results show a decrease in gastric lipolysis when interfacially active molecules are incorporated into a food matrix. However, only the Sn-2 monopalmitin caused a systematic decrease in triglyceride hydrolysis throughout the gastro-intestinal tract. This effect is most likely due to exclusion of both lipase and triglyceride from the water–oil interface together with a probable saturation of the solubilization capacity of bile with monoglycerides. Addition of β-lactoglobulin or lysophopholipids increased the hydrolysis of fat after the gastric phase. These results can be attributed to an increasing interfacial area with lipase and substrate present at the interface. Otherwise, β-lactoglobulin, or lysophopholipids reduced fat hydrolysis in the stomach. From the mathematical modeling of the interface composition, we can conclude that Sn-2 monopalmitin can desorb lipase from the interface, which, together with exclusion of substrate from the interface, explains the gradually decreased triglyceride hydrolysis that occurs during the digestion. Our results provide a biophysics approach on lipolysis that can bring new insights into the problem of fat uptake

Handens verk

Handens verk Innehållsförteckning – Värdet av att kunna lappa och återbruka av Pia Prost – En skinngarvarmästares kärlek till hantverket av Hanna Nore – En stickatröja för livet av Cecilia Lundberg – Ryorna bär på många hundratals år av historia av Pia Prost – Hantverk som levebröd av Joel Simberg – Dokumentationen viktig när segeljakten Alanta byggs av Petter Mellberg – Högkvalitativa produkter av säl kan inte säljas av Pia Prost – Hållbart hantverk i skärgården av Lena Långbacka – Sjöhistoria och marinarkeologi av Mikko Huhtamies – Bebyggelse och bosättning i Barösunds yttre skärgård av Krister Hamberg – Aktiv byaverksamhet i Barösund av Anders Holmberg – SKÄREN – skärgårdshistoria på webben av Eva-Marie Backnäs – Marslars-Birger av Cecilia Lundberg – Vackert ode till Skärgårdshavet av Cecilia Lundberg – Ålänningar i Nicaragua och lastångarens sista resa av Thure Malmberg – Hur de åländska kvinnorna banade väg ombord av Cecilia Lundberg – Skärinytt – Sista bilde

Using Nature´s concepts to synthesize materials - an example of biomimetic chemistry

Nature is a master of preparative chemistry and there is currently considerable interest in copying Nature in the design and synthesis of advanced materials – biomimetic supramolecular chemistry. In the article three examples of such procedures are given. The first example relates to ordered mesoporous materials, which are of interest for catalysis. The approach taken to synthesize the porous materials resembles the way some marine organisms, e.g. diatoms, build porous structures. The second example concerns the spider thread. The thin threads that the spiders produce are exceptional. Calculated per weight they have higher tensile strength than steel. The threads are proteinaceous materials and the secret behind their strength lies in the way the protein molecules assemble so that they all contribute in taking up the load. Synthetic fibers are made based on the same concept. The third example relates to the blue mussel adhesive. The blue mussel’s ability to stick to all kinds of surfaces – stone, iron, wood, plastics, etc. – is remarkable and it is particularly impressive that it does so in water in spite of the fact that the glue is water-based. Mimicking this would be a way to glue – or paint – a surface under wet conditions, possibly under water. Also the blue mussel adhesive is a proteinaceous material and it is believed that the key elements are catechol structures. Such structures are present in the amino acid DOPA and the proteins that make up the threads are rich in DOPA. Polymer chemists have adopted this approach and introduce catechol units on synthetic polymers as a way to mimic Nature’s adhesive