Novel nanostructured microfibrillated cellulose–hydroxypropyl methylcellulose films with large one-dimensional swelling and tunable permeability

Microfibrillated cellulose (MFC) films containing the water soluble and pharmaceutically approved polymer hydroxypropyl methylcellulose (HPMC) exhibited an unexpected decrease in permeability and excellent one-dimensional swelling properties above a threshold in HPMC content. It is proposed that the observed material characteristics derive from the influence of HPMC on the aggregation behavior of MFC in such a way that above a critical HPMC content the films are created through self assembly into a layered structure, composed of low swelling layers with swellable inter layer regions. The suggested structures were supported by high resolution microscopy. The findings should hold potential for direct applications, but even more as a concept for future material design

Determination of the glass transition of powder samples using Dynamic Mechanic Analysis on compacts

Dynamic Mechanic Analysis, DMA, is a sensitive method to determine the glass transition temperature (Tg) of materials. Several different sample geometries such as three point bending, stretched films or compressed cylinders, are commonly used. The Tg of a powder is related to its “sticky point”, i.e. the temperature when the powder particles interact instead of flowing freely. The determination of powder Tg is not straightforward using DMA due to the limiting geometry. Here it is demonstrated that the Tg of powder samples can be effectively and correctly determined by DMA on compacts in compression mode, using a standard wedge shaped probe usually utilized in three point bend analysis. The analysis of compacts holds the benefits of analysing powder samples as received from manufacturers, being relatively robust with regard to deformation as the material becomes rubbery, and enabling easy sample preparation and handling

High Performance Polysodium Acrylate Superabsorbents Utilizing Microfibrillated Cellulose to Augment Gel Properties

Microfibrillated cellulose was utilized at low concentrations as a filler material, added prior to free radical polymerization, in cross-linked superabsorbent polysodium acrylate hydrogels. The effect of microfibrillated cellulose concentration on equilibrium swelling, shear modulus after synthesis, and shear modulus at equilibrium swelling was studied at different degree of cross-linking. For the characterization of the microfibrillated cellulose optical microscopy, atomic force microscopy, and transmittance analysis were used. The shear modulus of the samples was determined using uniaxial compression analysis. The swelling of the gels was determined using classical gravimetrical measurements. It was found that microfibrillated cellulose was highly efficient in increasing the shear modulus of the gels. Furthermore, the microfibrillated cellulose was found to have the same effect on the swelling and shear modulus at equilibrium swelling as the same mass of the conventional covalent cross-linker N,N'-methylenebisacrylamide (MBA), while in fact improving the fracture resistance of the gels. In conclusion, microfibrillated cellulose shows great potential as an additive to enhance the performance of soft materials

Effect of calcium neutralization on elastic and swelling properties of crosslinked poly(acrylic acid) - correlation to inhomogeneities and phase behaviour

Crosslinked hydrogels of poly(acrylic acid) neutralized with calcium hydroxide were synthesized using free radical co-polymerization. The effects of the amount added calcium on the elastic modulus and swelling properties of the gels and the correlation to phase behaviour and structural changes within the gels were studied using texture analysis, gravimetric analysis, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis and atomic force microscopy (AFM). It was found that the elastic modulus decreased nonlinearly with increasing amount of added calcium and that the swelling's dependence on the amount of added calcium was complicated. The maximum swelling increased with increasing amount of added calcium until a critical calcium content was reached, upon which the gels phase separated, with a strong decrease in swelling as a result. The changes in properties are explained by the fact that calcium affects the structure of the polymer network during synthesis and by the phase behaviour of the gels. Changes in the gel structure with the addition of calcium were detected with AFM. Furthermore, AFM revealed different phases on the nanometre scale for the sample with a calcium content around which phase separation is macroscopically observed. Finally, it was shown that the sulphur from the initiator potassium persulfate formed crystal like regions with high sulphur and calcium content upon drying of the hydrogels

Probing interactions in combined hydroxide base solvents for improving dissolution of cellulose

To further understand cellulose-solvent interactions in aqueous hydroxide solutions, cellulose behavior in aqueous solutions of NaOH combined with tetramethylammonium hydroxide (TMAH) or benzyltrimethylammonium hydroxide (Triton B), as well as urea, was investigated. The rheological properties of the solutions were assessed throughflowsweeps at different temperatures, and the intermolecular interactions were probed using solvatochromic dyes. The results showed that NaOH combined with TMAH had synergistic effects on cellulose dissolution and was a better solvent for cellulose than the combination of NaOH with Triton B, in spite of the superior dissolution ability of Triton B alone. This somewhat unexpected finding shows that the base pair needs to be selected with care. Interestingly, addition of urea had no significant effect on the solvatochromic parameters or dissolution capacity of solutions of Triton B but rendered improved stability of solutions containing NaOH and/or TMAH. It seems that both urea and Triton B weaken the hydrophobic assembly effect of these solutions, but urea is excluded from interacting with cellulose in the presence of Triton B. This study provides further insight into dissolution of cellulose and the possibility of utilizing combinations of hydroxide bases to achieve improved solution properties

Effect of ethanol on the water permeability of controlled release films composed of ethyl cellulose and hydroxypropyl cellulose

The robustness of controlled release formulations when co-ingested with alcohol is a current concern expressed by regulatory authorities, especially with regard to dose dumping. One such controlled release formulation commonly used is film coating composed of ethyl cellulose (EC) and hydroxypropyl cellulose (HPC). The aim of this study was to investigate how the presence of ethanol in the dissolution medium affects the water permeability of such films. Film samples were prepared in various EC–HPC compositions, and the effect of different ethanol concentrations in the dissolution medium on the permeability was studied using a modified Ussing chamber and tritiated water. It was found that the effect of ethanol on the film permeability varied depending on the composition of the films. The results were interpreted in terms of swelling of the EC in the films, where the swelling increased with increasing ethanol concentration. Thus, for films with low HPC content (non-interconnected pores), the water permeability of the films increased with increasing ethanol concentration as the diffusion through the ethyl cellulose increased due to swelling. However, for films with higher HPC content (having interconnected pores through the films), the permeability decreased, likely due to the swelling of the ethyl cellulose blocking the pores. The interpretation of the results was supported by dynamic mechanic analysis and SEM analysis

Dissolution of cellulose using a combination of hydroxide bases in aqueous solution

In order to further understand the role of the cation when dissolving cellulose in aqueous solutions of hydroxide bases, different bases were combined in solution. Up to 5 wt.% of microcrystalline cellulose was dissolved using a combination of NaOH and the organic base tetramethylammonium hydroxide (TMAH) in water at low temperatures. Thermoscans of solutions containing both NaOH(aq) and TMAH(aq) indicated that cellulose interaction with TMAH seems to be favoured over NaOH. Dynamic rheology measurements of the solutions revealed that combining the two bases delayed gelation significantly when compared to cellulose dissolved in NaOH(aq) or TMAH(aq) alone. Intrinsic viscosity of cellulose in the combined NaOH- and TMAH(aq) solutions was slightly higher than that of the single-base solutions, indicating a slight increase in solvent quality. This shows that combining bases may lead to synergies that improve solvent stability without requiring the use of other additives. Graphic abstract: [Figure not available: see fulltext.]

Promotion of biodiversity at cemeteries : case study of two cemetery environments

Biologisk mångfald är avgörande för att ekosystem ska fungera och kunna leverera de ekosystemtjänster som efterfrågas i vårt samhälle och som gör nytta för oss människor. Sverige har genom FN:s Konvention för biologisk mångfald åtagit sig att bevara och nyttja den biologiska mångfalden på ett hållbart sätt och ”Ett rikt växt- och djurliv” är sedan 2005 ett av Riksdagens 16 nationella miljökvalitetsmål. Värdefull natur skyddas och åtgärdsprogram tas fram för att skydda våra mest hotade arter, då många arter i dagens samhälle är hårt trängda och riskerar att dö ut. Olika samhällssektorer kan bidra till att bevara och öka den biologiska mångfalden på de platser där man verkar, genom att använda brukar- och skötselmetoder som är hållbara och värnar om växt- och djurlivet. Då många av landets kyrkogårdar har stora natur- och kulturvärden har Svenska kyrkan en viktig uppgift i att förvalta och vårda vårt kulturarv, vilket även inbegriper det biologiska kulturarvet. De styrdokument som finns inom Svenska kyrkan idag hjälper förvaltningarna till en medvetenhet och ett miljötänk som återspeglar sig i det vardagliga arbetet, vilket i många fall även bidrar till att bevara och utveckla den biologiska mångfalden. Kontinuiteten, dvs att inga större förändringar har skett, belyses som en viktig faktor för biologisk mångfald på kyrkogården jämfört med andra miljöer. Kontinuitet gynnar sällsynta växter och djur och kyrkogården har på så vis fungerat som en slags oas och fristad där en mångfald av arter nischat sig och överlevt i samband med att det omgivande landskapet förändrats. Huvudsyftet med arbetet har varit att lyfta fram och synliggöra vilka biotoper som generellt är möjliga att gynna på kyrkogården samt hur man som kyrkogårdsförvaltare kan arbeta för att främja dessa. Arbetet inleds med en litteraturstudie för att belysa varför biologisk mångfald behövs samt för att inhämta fakta kring olika biotoper på kyrkogården. I litteraturstudien undersöks även vilka styrdokument som kyrkogårdsförvaltningarna har att tillgå och använder sig av i sitt arbete. Genom intervjuer och observationer har komparativa fallstudier också utförts på en stor respektive en liten kyrkogård. Jämförelser har gjorts för att få reda på eventuella skillnader och vilka faktorer som påverkar hur de båda förvaltningarna arbetar med biologisk mångfald, samt vilka biotoper de prioriterar. Resultatet visar på att många av de biotoper som studerats är unika för kyrkogårdsmiljön, de återfinns inte någon annanstans i vårt landskap och blir därmed mycket viktiga att värna om. Våra kyrkogårdar släpar envist med sig ett skötselideal som innebär att man nitiskt städar varje hörn för att det ska se prydligt ut. Med mer naturinslag och sänkta skötselambitioner kommer generellt en ökad artrikedom, men studien visar på att det många gånger kan leda till att den biologiska mångfaldens intressen hamnar i konflikt med de estetiska och sociala värdena. Inne i städerna är kyrkogårdarna en del av stadens grönstruktur och blir därmed också viktiga områden för rekreation och utevistelse. Fallstudierna visar på två ytterligheter av kyrkogårdsmiljöer, vilket har genereratBiodiversity is crucial for ecosystems to function and for their ability to deliver the ecosystem services requested in our society and that benefit us people. Sweden has, through the UN Convention on Biological Diversity, committed itself to conserving and using biodiversity in a sustainable way, and "A rich plant and wildlife" has since 2005 been one of the Riksdag's 16 national environmental quality objectives. Valuable nature is protected and action programs are being developed to protect our most threatened species, as many species in today's society are severely threatened and at risk of extinction. Different sectors of society can help to conserve and increase biodiversity in the places where one operates, using sustainable management methods that cares for plant and wildlife. Since many of the country's cemeteries have great natural and cultural values, Svenska kyrkan has an important task in managing and care for our cultural heritage, which also includes the biological heritage. The governing documents in Svenska kyrkan today help the cemetery managements to an awareness and environmental thinking that reflects in everyday work, which in many cases also helps to preserve and develop biodiversity. Continuity, when no major changes have been made, is highlighted as an important factor for biodiversity in the cemetery compared to other environments. Continuity favors rare plants and animals, and the cemetery has thus served as a kind of oasis and sanctuary where a variety of species survived as the surrounding landscape changed. The main purpose of the work has been to highlight and visualize which biotopes that generally are possible to promote at cemeteries and how to work to promote them. A literature study has been made to show why biodiversity is important and to gather facts about different biotopes in the cemetery. The literature study also examines the governing documents available to the cemetery managements and how they can be at use in their work. Through interviews and observations, comparative case studies also have been conducted at one large and one small cemetery. Comparisons have been made to find out any differences and what factors affect the way the two managements work with biodiversity, and what biotopes they prioritize. The result shows that many of the biotopes studied are unique to the cemetery environment, they are not found elsewhere in our landscape and are therefore very important to conserve and promote. Traditionally, our cemeteries have always been well-kept and tidy and the visitors are used to this neat appearance. With more natural elements and lowered management ambitions there is generally an increased amount of species, but the study also shows that the biological values often tend to get into conflict with the aesthetic and social values. In the cities, the cemeteries are part of the city's green structure and thus also become important areas for recreation and outdoor activities. The study shows two extremes of cemetery environments, which has generated a variety of factors that can affect the managements ability to promote biodiversity

Stick–slip motion and controlled filling speed by the geometric design of soft micro-channels

HypothesisLiquid can move by capillary action through interconnected porous materials, as in fabric or paper towels. Today mass transport is controlled by chemical modification. It is, however, possible to direct mass transport by geometrical modifications. It is here proposed that it is possible to tailor capillary flow speed in a model system of micro-channels by the angle, size and position of attached side channels.ExperimentsA flexible, rapid, and cost-effective method is used to produce micro-channels in gels. It involves 3D-printed moulds in which gels are cast. Open channels of micrometre size with several side channels on either one or two sides are produced with tilting angles of 10 – 170\ub0. On a horizontal plane the meniscus of water driven by surface tension is tracked in the main channel.FindingsThe presence of side channels on one side slowed down the speed of the meniscus in the main channel least. Channels having side channels on both sides with tilting angles of up to 30\ub0 indicated tremendously slower flow, and the liquid exhibited a stick-slip motion. Broader side channels decreased the speed more than thinner ones, as suggested by the hypothesis. Inertial forces are suggested to be important in branched channel systems studied here

Evaluation of Carboxymethyl-Hexanoyl Chitosan as a Protein Nanocarrier

Carboxymethyl‐hexanoyl chitosan (CHC) has the ability to self‐assemble into nanocapsules in an aqueous solution and it has recently shown potential in numerous biomedical applications. Here we investigate the protein loading efficiency and release, as well as the structural properties of CHC protein nanocarriers. Bovine serum albumin (BSA) or its chromophore labelled version, fluorescein‐BSA, was used as a model protein and the loading was performed with a simple mixing of pre‐formed nanocapsules and protein. Dynamic light scattering and zeta potential analysis revealed that protein loaded nanocarriers with high positive zeta potential were formed. The protein loaded nanocarriers displayed a loading efficiency of 75% and a very slow protein release. In summary, our results highlight the potential of CHC as a protein nanocarrier, but also indicate that protein‐CHC interactions need to be considered in protein containing CHC formulations where protein release is not the main function