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Adsorption of fucoidan and chitosan sulfate on chitosan modified PET films monitored by QCM-D
Tea Indest, Janne Laine, Leena Sisko Johansson, Karin Stana-Kleinschek, Simona Strnad, Renate Dworczak, Volker Ribitsch, 2009, izvirni znanstveni članek

Opis: The adsorption behavior of fucoidan as well as chitosan derivatives (chitosan sulfate) on poly(ethylene terephthalate) (PET) model film surface was studied using the quartz crystal microbalance technique. These systems were chosen for this study due to their promising biocompatible properties. Moreover, fucoidan and chitosan sulfate have promising anticoagulant properties and represent an alternative to heparin treatment of vascular grafts. As a first step, PET foils were activated by alkaline hydrolysis to increase their hydrophilicity. From these foils, model PET films were prepared by the spin coating technique on a silica quartz crystal. The selected polysaccharides (chitosan, fucoidan, and chitosan sulfate) were adsorbed from aqueous solutions on the PET surfaces. The adsorption was monitored using a quartz crystal microbalance with a dissipation unit. The surface chemistry and morphology of the chitosan/fucoidan or chitosan/chitosan sulfate coated PET-H films was analyzed using XPS and AFM. It was found that chitosan/fucoidan films were thinner and more compressed, while in the case of chitosan/chitosansulfate, large amounts of chitosan sulfate were adsorbed, indicating a loose and thick adsorbed film.
Ključne besede: PET films, fucoidan, chitosan sulfate, adsorption, anticoagulant properties
Objavljeno: 01.06.2012; Ogledov: 1147; Prenosov: 56
URL Povezava na celotno besedilo

Topochemical modification of cotton fibres with carboxymethyl cellulose
Lidija Fras Zemljič, Peer Stenius, Janne Laine, Karin Stana-Kleinschek, 2008, izvirni znanstveni članek

Opis: The research reported in this paper demonstrates that the capacity of cotton fibres to adsorb cationic surfactants as well as the rate of the adsorption process can be increased by adsorbing carboxymethyl cellulose (CMC) onto the fibre surfaces; in addition, the adsorption can be restricted to the fibre surface. CMC was deposited by means of adsorption from an aqueous solution. The adsorption of N-cetylpyridinium chloride (CPC) from an aqueous solution onto the CMC-modified fibres was measured using UVspectrometric determination of the surfactant concentration in the solution. Adsorption onto the cotton fibres was studied in a weakly basic environment (pH 8.5) where cotton fibres are negatively charged and the CPC ion is positively charged. Modification of the fibres by adsorption of CMC introduces new carboxyl groups onto the fibre surfaces, thereby increasing the adsorption capacity of the fibres for CPC. The initial rate of adsorption of CPC increased proportionally with the amountof charge; however, this rate slowed down at high degrees of coverage onfibres with a high charge. The adsorption of cationic surfactant to the anionic surface groups was stoichiometric, with no indication of multilayer oradmicelle formation. It was evident that the acidic group content of the fibres was the primary factor determining cationic surfactant adsorption to these fibres.
Ključne besede: textile fibres, cotton fibres, modification, carboxymethyl cellulose, acid groups, charge increase, conductiometric titration, phenol-sulphuric acid test, practical applications
Objavljeno: 01.06.2012; Ogledov: 1096; Prenosov: 71
URL Povezava na celotno besedilo

X-ray study of pre-treated regenerated cellulose fibres
Majda Sfiligoj-Smole, Zdenka Peršin, Tatjana Kreže, Karin Stana-Kleinschek, Volker Ribitsch, Susanne Neumayer, 2003, izvirni znanstveni članek

Opis: Regenerated cellulose fibres have had an important role to play in the man-made fibre field. The very special characteristics of different types of regenerated cellulose fibres, e.g. mechanical properties, sorption characteristics, and aesthetics were conditioned by the differences in their fine structure due to fibre formation processes. Additionally, the finishing processes could influence the fibre structure. A study was done of the crystalline structures of a solvent-spun cellulose fibre type (Lenzing Lyocell), made according to the NMMO process, and two conventional cellulosic fibre types, made by the viscose process (Lenzing Viscose and Lenzing Modal). The fibres were pre-treated (bleached and slack mercerised) and structural changes were followed by wide angle and small angle x-ray scattering (WAXS and SAXS), respectively. The periodical structure, determined by long spacing, was nearly the same in all the different types of fibres. A slight increase was observed after the treatment of viscose and modal fibres, but an unpronounced fall of a long period accompanied the pre-treatment of lyocell fibres. Some changes in crystallinity and crystalline orientation occurred due to the treatment conditions. The structural changes were correlated to the iodinesorption and mechanical properties.
Ključne besede: regenerated cellulose fibres, fibre structure, fibre properties, x-ray analysis, WAXS, SAXS, cellulose pre-treatment
Objavljeno: 01.06.2012; Ogledov: 1255; Prenosov: 51
URL Povezava na celotno besedilo

The influence of structural properties on the dye diffusion and dyeability of PA 6 fibres
Simona Strnad, Slava Jeler, Karin Stana-Kleinschek, Tatjana Kreže, 2003, izvirni znanstveni članek

Opis: The relationships were investigated between the structural and dyeing properties of different structurally modified PA 6 fibers. PA 6 monofilament yarn samples were applied having different crystalline degrees and different content of alpha, respectively gamma crystalline modification. The diffusion coefficients of two different acid dyes were determined together with the content of dyestuff absorbed (under specific conditions) by fiber samples. In order to estimate colorimetry method from the viewpoint of polymer structural change detection, the colors of the dyed PA 6 samples were determined (L*, a*,b*, C*, h coordinates) and the color differences (L*, a*, b*, C*, H*, E*) were calculated between untreated standard and structurally modified samples. The dyeability of PA 6 fibers depended mainly on the way in which crystallinity had been achieved, i.e. on the materialćs history. Different crystalline modifications caused different sorption properties and fiber dyeability. Smaller increases (app 20%) of crystallinity degree caused a decrease in diffusion coefficients. Contrary to expectations, the significant increase of crystallinity degree (app 50%) had an influence on the increase ofdyeability, presumably owing to the formation of larger empty spaces in the structure. The results achieved by colorimetry were in good correlation with dye absorption measurements. The colorimetry of dyed fiber samples was sensitive enough to detect even small differences in the quantities of absorbed dyestuff.
Ključne besede: textiles, PA 6 fibres, dyeing, dyeability, fibre structure, crystallinity, chemical modification
Objavljeno: 01.06.2012; Ogledov: 1458; Prenosov: 14
URL Povezava na celotno besedilo

Application of spectrophotometric methods in assessing the influence of alkaline treatment on the degree of crosslinking of cotton cellulose with BTCA
Olivera Šauperl, Karin Stana-Kleinschek, Bojana Vončina, Majda Sfiligoj-Smole, Alenka Majcen Le Marechal, 2003, izvirni znanstveni članek

Opis: Polycarboxylic acids appear to be the most promising nonformaldehyde crosslinking agents to replace the traditional, mostly formaldehyde-based, compounds. The most effective among these acids is 1,2,3,4-butanetetracarboxylic acid (BTCA). In this study, a comparison was made of the crosslinking effect on mercerized and on unmercerized as well as with different BTCA mass fractions crosslinked cotton fibres using FT-IR spectroscopy, the methylene blue method and water retention determination. The main purpose of the research was to evaluate how the structural changes of mercerized cotton (transformation of cellulose I into cellulose II) influence the crosslinking of cellulose fibres.
Ključne besede: textile fibres, cotton fibres, cotton cellulose, mercerization, crosslinking
Objavljeno: 01.06.2012; Ogledov: 1403; Prenosov: 71
.pdf Celotno besedilo (169,10 KB)
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Functional materials from polysaccharides
Volker Ribitsch, Karin Stana-Kleinschek, 2013, objavljeni povzetek znanstvenega prispevka na konferenci (vabljeno predavanje)

Ključne besede: polisaharidi
Objavljeno: 10.07.2015; Ogledov: 868; Prenosov: 18
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Application and characterization of microstructured cellulose thin films
Rupert Kargl, Tamilselvan Mohan, Aleš Doliška, Karin Stana-Kleinschek, Volker Ribitsch, 2013, objavljeni znanstveni prispevek na konferenci

Ključne besede: celuloza
Objavljeno: 10.07.2015; Ogledov: 735; Prenosov: 6
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Heike M. A. Ehmann, 2012, doktorska disertacija

Opis: The goal of this thesis is the structuring of cellulose nanocrystals using different organofunctional silane compounds and different cationic species to prepare highly functional materials with tailored properties. In addition different new aspects and approaches for the structural characterization of functionalised cellulose nanocrystals (CNC) functionalised with different organofunctionalalkoxysilanes as well as cationic species have been introduced. Cellulose nanocrystals (CNC) are prepared using three different acidic conditions to hydrolyse microcrystalline cellulose (MCC). The sulphuric acid hydrolysis introduces highly negative charged sulphate groups on the CNC. The aqueous nanocrystalline cellulose suspensions (aNCS) are analysed in terms of ζ-potential related to the pH and concentration to investigate the stability while dynamic light scattering (DLS) is used to investigate the size distribution. The hydrochloric acid hydrolysis in contrast only removes the amorphous regions but the so obtained CNC are less stabilized (decreased ζ-potential) and tend to agglomerate very fast. The use of the mixture of both acids (HCl and H2SO4) during the hydrolysis of MCC introduces less sulphate groups compared with the sulphuric acid hydrolysis. AFM investigations show that the shapes of the CNC are highly influenced by the hydrolysis conditions. While the shape of the H2SO4 hydrolysed CNC is rod like, while the shape of the other two CNC samples is more spherical in nature. One of the major topic in this work is the analysis of aNCS in aqueous solutions by small angle x-ray scattering (SAXS). The use of the generalized indirect Fourier transformation (GIFT) method allows the analysis of these systems and structural properties such as shape, size and surface charge of aNCS can be assessed. Using this kind of characterisation it can be seen that the shape of the H2SO4 hydrolysed CNC is definitely rod like while the other CNC sample can be described with spheres. In addition to the aNCS characterisation different substrates (Si-wafer, glass slides, polystyrene, etc.) are equipped with aNCS using a variety of different deposition methods (e.g. spin coating, solution casting, dip coating). The resulting films are studied in terms of morphology AFM, SARFUS and SEM. Sophisticated scattering techniques are employed for surface structural characterisation as grazing incidence small angel x-ray scattering. The determination of surface free energies allows conclusions about the hydrophilicity and hydrophobicity as well as the interaction capacity with different liquids. It can be seen that besides the hydrophilic nature of the CNC also hydrophobic interactions are present. The highly negative charged CNC sample which was prepared using sulphuric acid hydrolysis is found to be best suitable for the further hybridization with different organofunctional silanes and for the layer by layer approach (LBL) with different cationic species. The organofunctionalalkoxysilanes which were used in this study can be divided into three groups (e.g filler, surface functionalisation silanes, cross linking silanes). Depending on the nature of the organic residue the silanes are capable to introduce functionalities with enhanced hydrophobic and olephobic properties. The surface energies are investigated using contact angle method, while the surface energies are calculated using three different model approaches (OWRK, Wu, Acid-Base). The most increased hydrophobic and oleophobic properties were measured for trimethylfluorophenylsilantriol (PFTEOS). The morphology of the coated silanes is investigated using SAFRUS technique. It can be seen that nearly all silanes can be coated as homogeneous films onto different substrates (Si-wafer, SURFs, glass slides) with different methods (spin coating, solution casting). The macroscopic appearance of solution casted silanes is investigated using optical microscopy. The differences of the structural nature of the so obtained coatings and detaching films were investigated...
Ključne besede: Cellulose nanocrystals, sol-gel chemistry, organofunctionalalkoxysilanes, hybrid materials, small angle x-ray scattering, generalized indirect Fourier Transformation, quartz crystal microbalance dissipation, surface free energy, surface functionalisation, layer by layer
Objavljeno: 28.11.2012; Ogledov: 1618; Prenosov: 98
.pdf Celotno besedilo (8,59 MB)

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