The Measurement of Polymer Swelling Processes by an Interferometric Method and Evaluation of Diffusion Coefficients

The amorphous polymer film swelling in a liquid solvent below the glass transition temperature was characterized by a few kinetic parameters (especially the mutual diffusion coefficient of swelling and its mean value) obtained by interference of monochromatic light in the wedge arrangement. This interferometric method allows one to determine the concentration field in the swollen surface layer and consequently to compute the concentration-dependent diffusion coefficient. A software system developed at the Department of Physics and Material Engineering at TBU in Zlin has been used for the evaluation of the main kinetic parameters of the swelling process. The software can be used for the on-line analyses of interferograms during the swelling process. The main application outputs are the computation of the concentration profile, the concentration gradient, the mutual diffusion coefficient of the swelling by the solvent and its mean value

The behaviour of hyaluronan solutions in the presence of Hofmeister ions: A light scattering, viscometry and surface tension study

Dynamic light scattering (DLS), viscosity and surface tension (SFT) measurements were used to characterize influence of salts containing ions of Hofmeister series (Na 2 SO 4 , (NH 4 ) 2 SO 4 , NaSCN, NH 4 SCN and NaCl) on the behaviour of hyaluronan in diluted solutions at a temperature range of 15–45 °C. The results of the study showed that chaotropic and kosmotropic ions notably influenced the folding and unfolding of hyaluronan coils due to interactions between a respective ion and hydrophilic or hydrophobic patches present in the backbone of the polymer chains. This was mainly proved by viscosity and light scattering measurements. The temperature dependence of the hydrodynamic diameter of the hyaluronan coil determined by DLS demonstrated that combinations of chaotropic and kosmotropic ions in one salt (NaCl, NaSCN and (HN 4 ) 2 SO 4 ) can stabilize the size of the coil in a wide range of temperatures. Tensiometry measurements indicated that certain types of ions present in the solution caused an unfolding of the hyaluronan coils, leading to a decrease of SFT. © 2019 Elsevier LtdMinistry of Education, Youth and Sports of the Czech Republic - Program NPU I [LO1504]; TBU in Zlin [IGA/FT/2017/011, IGA/FT/2018/011, IGA/FT/2019/012

Stability of aqueous polymeric dispersions for ultra-thin coating of bi-axially oriented polyethylene terephthalate films

The stability of polyacrylate and polyester based aqueous dispersions designed for ultrathin coating of extruded plastic films, especially bi-axially oriented polyethylene terephthalate (BOPET), was studied. Also, the effect of the gemini surfactant based defoaming/wetting agent on the properties of the dispersions was examined. The addition of the defoaming/wetting agent resulted in reducing the surface free tension of the polyacrylate and polyester dispersion by 15% and 20%, respectively and the initial foam height by 60% and 15%, respectively. At the same time, the agent addition did not compromise the temperature and pH stability of the dispersions. Such modified dispersion can be utilized for ultrathin coating of plastic film used for packaging, to improve their processability, printability, and metallization.European Regional Development Fund (ERDF); national budget of the Czech Republic [CZ.1.05/2.1.00/03.0111]; Ministry of Education, Youth and Sports of the Czech Republic-Program NPU I [LO1504]; European Regional Development Fund [CZ.1.05/2.1.00/19.0409

Electrospinning of hyaluronan using polymer coelectrospinning and intermediate solvent

In the current study, we present methods of sodium hyaluronate, also denoted as hyaluronan (HA), nanofiber fabrication using a direct-current (DC) electric field. HA was spun in combination with poly(vinyl alcohol) (PVA) and polyethylene oxide (PEO) and as a pure polymer. Nonaggressive solvents were used due to the possible use of the fibers in life sciences. The influences of polymer concentration, average molecular weight (Mw), viscosity, and solution surface tension were analyzed. HA and PVA were fluorescent-labeled in order to examine the electrospun structures using fluorescence confocal microscopy. In this study, two intermediate solvent mixtures that facilitate HA electrospinning were found. In the case of polymer co-electrospinning, the effect of the surfactant content on the HA/PVA electrospinning process, and the effect of HA Mw on HA/PEO nanofiber morphology, were examined, respectively. © 2019 by the authors

Preparation of textured surfaces on aluminum-alloy substrates

The ways of producing porous-like textured surfaces with chemical etching on aluminum-alloy substrates were studied. The most appropriate etchants, their combination, temperature, and etching time period were explored. The influence of a specifically textured surface on adhesive joints' strength or superhydrophobic properties was evaluated. The samples were examined with scanning electron microscopy, profilometry, atomic force microscopy, goniometry, and tensile testing. It was found that, with the multistep etching process, the substrate can be effectively modified and textured to the same morphology, regardless of the initial surface roughness. By selecting proper etchants and their sequence one can prepare new types of highly adhesive or even superhydrophobic surfaces. © 2018 by the authors.Ministry of Education, Youth, and Sports of the Czech Republic-Program NPU I [LO1504]; European Regional Development Fund [CZ.1.05/2.1.00/19.0409]; TBU grant [IGA/FT/2017/011, IGA/FT/2018/011

Variations of polymer porous surface structures via the time-sequenced dosing of mixed solvents

A new approach to polystyrene surface treatment via the time-sequenced dispensing of good and poor solvent mixtures on the rotating surface of treated substrate is presented in this study. It is demonstrated that the variation of the sequencing together with other variables (e.g., temperature and solvent concentration) affects the size and depth of pores evolving on the polystyrene surface. A model of the surface pore creation, associated with the viscoelastic phase separation, surface tension, and secondary flows caused by temperature variations and the rapid evaporation of the good solvent is proposed. Experimental results of profilometric, goniometric, and optical measurements show that this approach enables the simple and quick preparation of surfaces with various numbers, diameters, and depths of individual pores, which ultimately affects not only the wetting characteristics of the surfaces but also the fate of cells cultivated there. The presented method allows the easy preparation of a large number of structured substrates for effective cell cultivation and proliferation. © 2017 American Chemical Society.CZ.1.05/2.1.00/19.0409, ERDF, European Regional Development Fund; MOE, Ministry of EducationOperational Program Research and Development for Innovations - European Regional Development Fund (ERDF); national budget of the Czech Republic within the framework of the project Centre of Polymer Systems [CZ.1.05/2.1.00/03.0111]; Ministry of Education, Youth and Sports of the Czech Republic, Program NPU I [LO1504]; European Regional Development Fund [CZ.1.05/2.1.00/19.0409]; TBU [IGA/FT/2015/014, IGA/FT/2016/013]Operational Program Research and Development for Innovations - European Regional Development Fund (ERDF); national budget of the Czech Republic within the framework of the project Centre of Polymer Systems [CZ.1.05/2.1.00/03.0111]; Ministry of Education, Youth and Sports of the Czech Republic, Program NPU I [LO1504]; European Regional Development Fund [CZ.1.05/2.1.00/19.0409]; TBU [IGA/FT/2015/014, IGA/FT/2016/013

Factors determining self-assembly of hyaluronan

The conditions determining network-forming and aggregation properties of hyaluronan on the mica surface were studied. The hyaluronan was deposited on the surface from aqueous and saline solutions and attached by a bivalent cation. The morphology of the immobilized assemblies was characterized by atomic force microscopy. The experimental results show that the morphology and size of the aggregates as well as the density of the interconnecting fibrillar network, both made of hyaluronan, at the liquid-solid phase interface are determined not only by its molecular weight or concentration in solution, but also by the dissolution conditions and storage time. These findings extend the current state of knowledge about the conformational variability of this biologically important polymer. Understanding the conformational variability is of great importance, as it governs the physiological functions of hyaluronan, as well as its processability and formulations. That in turn determines its usability in different pharmacological and biomaterial applications. © 2020 Elsevier LtdBayerisch-Tschechische Hochschulagentur BTHA/BAYHOST [LTAB19019]; Ministry of Education, Youth and Sports of the Czech Republic DKRVO [RP/CPS/2020/003]; TBU grant [IGA/FT/2020/005]; Ministry of Education, Youth and Sports of the Czech RepublicMinistry of Education, Youth & Sports - Czech Republi

Modern types of PVD/PACVD coatings used for injection molds and their effects on selected physical properties of mold cavities

This research paper deals with an effect of injection mold core/cavity surface and their additional treatment on selected optical properties and surface quality of these tool parts. Used mold cavities were made from tool steels 1.2343 (chromium-molybdenum-vanadium-silicon steel with good hardenability) and 1.2083 (martensitic steel with high chromium content), their surface was polished to the roughness of Ra = 0.08 microns (manufacturer guaranteed mirror finish). For purposes of an experiment, injection mold with interchangeable core/cavities was designed and manufactured. Subsequently, simple shape cavities were manufactured (plates with dimensions of 120 × 120 mm) and further were provided with a specific coating in order to change surface properties. In total, three types coatings were applied; CrN, AlTiN and hydrogenated a-C:H coatings. All cavities were measured using 3D non-contact roughness tester in different areas in cavity (totally 8 areas per cavity were selected in various distances from polymer inlet). Specifically, surface gloss under different reflection angles with respect to coating or tool steel type was evaluated from optical properties. The results show that the additional surface treatment of injection mold cavity with coatings can reduce the values of roughness parameters, however, affect the level of core/cavity gloss. © 2017 TANGER Ltd., Ostrava.ERDF, European Regional Development Fun

Preparation of hierarchically structured polystyrene surfaces with superhydrophobic properties by plasma-assisted fluorination

The nanotexturing of microstructured polystyrene surfaces through CF4 plasma chemical fluorination is presented in this study. It is demonstrated that the parameters of a surface micropore-generation process, together with the setup of subsequent plasma-chemical modifications, allows for the creation of a long-term (weeks) surface-stable micro- and nanotexture with high hydrophobicity (water contact angle >150 degrees). Surface micropores were generated initially via the time-sequenced dosing of mixed solvents onto a polystyrene surface (Petri dish) in a spin-coater. In the second step, tetrafluoromethane (CF4) plasma fluorination was used for the generation of a specific surface nanotexture and the modulation of the surface chemical composition. Experimental results of microscopic, goniometric, and spectroscopic measurements have shown that a single combination of phase separation methods and plasma processes enables the facile preparation of a wide spectrum of hierarchically structured surfaces differing in their wetting properties and application potentials.Ministry of Education, Youth and Sports of the Czech Republic-Program NPU I [LO1504]; European Regional Development Fund [CZ.1.05/2.1.00/19.0409]; TBU [IGA/FT/2017/011, IGA/FT/2018/011, IGA/FT/2019/012

Characterization at 25°C of Sodium Hyaluronate in Aqueous Solutions Obtained by Transport Techniques

Mutual diffusion coefficients, D, were determined for aqueous solutions of sodium hyaluronate (NaHy) at 25°C and concentrations ranging from 0.00 to 1.00 g·dm-3 using the Taylor dispersion technique. From these experimental data, it was possible to estimate some parameters, such as the hydrodynamic radius Rh, and the diffusion coefficient at infinitesimal concentration, D0, of hyaluronate ion, permitting us to have a better understanding of the structure of these systems of sodium hyaluronate in aqueous solutions. The additional viscosity measurements were done and Huggins constant, kH, and limiting viscosity number, [η], were computed for interaction NaHy/water and NaHy/NaHy determination. © 2015, MDPI AG. All rights reserved.PTDC/AAC-CLI/118092/2010, FCT, Fuel Cycle TechnologiesFCT [PTDC/AAC-CLI/118092/2010]; Coimbra Chemistry Centre from the FCT [Pest-OE/QUI/UI0313/2014]; Centre of Polymer Systems [CZ.1.05/2.1.00/03.0111]; TBU in Zlin - specific university research and national budget of Czech Republic [IGA/FT/2013/015, IGA/FT/2014/018]; [SFRH/BD/72305/2010