Behavior of block-polyampholytes near a charged surface

The behavior of polyampholytes near a charged planar surface is studied by means of Monte Carlo simulations. The investigated polyampholytes are overall electrically neutral and made up of oppositely charged units (called blocks) that are highly charged and of the the same length. The influence of block length and substrate's surface-charge-density on the adsorption behavior is addressed. A detailed structural study, including local monomer concentration, monomer mean height, transversal chain size, interface-bond orientation correlation, is provided. It is demonstrated that adsorption is favored for long enough blocks and/or high enough Coulomb interface-ion couplings. By explicitly measuring the chain size in the bulk, it is shown that the charged interface induces either a swelling or a shrinkage of the transversal dimension of the chain depending, in a non trivial manner, on the block length.Comment: 23 pages - 10 eps figs. Submitted for publicatio

Comparison of methods for determining the effectiveness of antibacterial functionalized textiles

Antimicrobial functionalization of textiles is important for various applications, such as protection of textile materials from decomposition, generation of more effective wound dressings, and the prevention of infections or malodors resulting from bacterial growth. In order to test the efficacy of new products, their antibacterial activity needs to be evaluated. At present, several different procedures are being used for this purpose, hindering comparisons among different studies. The present paper compares five of these assays using a sample panel of different textiles functionalized with copper (Cu) and silver (Ag) as antibacterial agents, and discusses the suitability of these methods for different analytical requirements. Bacterial viability was determined by measuring the optical density at 600 nm, a colorimetric assay based on MTT (3-[4, 5-dimethylthiazol-2-yl]-2, 5 diphenyl tetrazolium bromide) conversion, an agar diffusion assay, and colony formation, either after culturing in media containing textile samples, or after recovery from textiles soaked with bacterial suspension. All experiments were performed with a Gram-negative (Escherichia coli) and a Gram-positive (Staphylococcus warneri) model organism. In general, the results yielded by the different methods were of good comparability. To identify the most suitable test system for the particular type of antibacterial coating, several factors need to be taken into account, such as choosing appropriate endpoints for analyzing passive or active antibacterial effects, selection of relevant microorganisms, correcting for potential interference by leaching of colored textile coatings, required hands on time, and the necessary sensitivity.DFG, 325093850, Open Access Publizieren 2017 - 2018 / Technische Universität Berli

Protein adsorption on preadsorbed polyampholytic monolayers

The adsorption behaviour of five different globular proteins on pure silicon substrates and on preadsorbed polyampholytic monolayers has been investigated as a function of protein concentration. The prelayers were prepared by adsorption of the ampholytic diblock copolymer poly(methacrylic acid)-block-poly ((dimethylamino)ethyl methacrylate) (PMAA-b-PDMAEMA). This polyampholyte adsorbs in densely packed micelles directly from aqueous solution. Ellipsometry was used to determine the amount of adsorbed polyampholyte and protein. While ATR-IR spectroscopy gives information about the adsorption and desorption behaviour of the preadsorbed polyampholytic layer, the lateral structures of the dried films were investigated by scanning force microscopy (SFM). The amount of protein adsorbed was found to be strongly influenced by the preadsorbed polyampholyte compared to the adsorption on the pure silicon substrates. No displacement of the polyampholyte by the proteins was detected. In most cases the protein adsorption was reduced by the preadsorbed polyampholytic layer. The observed trends are explained by the change in electrostatic and hydrophilic characteristics of the substrates. Furthermore, the entropy of adsorption has to be taken into account.Peer reviewe

Overview on natural dyes and their IR-spectra – Part I: Plant based dyes with naphthoquinone and anthraquinone structure

This is the first paper of a series of review articles reporting on natural dyes, their origin and infrared spectra (IR spectra). One aim of this review series is to compare IR spectra of natural dyes from different origin and discuss if this spectroscopic method can be used as versatile tool for the identification of natural dyes and their origin. This part I of the review series is related to four natural dyes based on the chemical structures of naphthoquinone and anthraquinone. Especially discussed are Lawson, juglone and alizarin, which are related to the natural products henna, walnut hull and madder root. Also, the natural dye based on alkanna root is investigated. Compared are the IR spectra of these natural dyes gained from different suppliers with the IR spectra of the pure chemical substances related to the natural dyes. A discussion with spectra from literature is supported. The aim of this review paper is to support infrared spectroscopic data of natural materials (natural dyes) to enable further material identification and also quality control supporting people working in the fields of fiber analytics or with production processes using natural dye

Comparison of conventional and digital lectures and examinations with respect to the conditions after COVID-19 period – an example for a bachelor lecture on textile finishing

Due to the appearance of COVID-19, many lectures and examinations at universities are forced to digital formats. In the first post-pandemic semester again, the change from digital to conventional lectures was demanded. By this background the question arises, what is the better format for lecture and exam – digital or conventional? This question is discussed on the example of a bachelor lecture on textile finishing for the time period from 2019 to 2023. The combination of digital lecture and digital exam leads to strong participation numbers and by this to more successfully passing students. If the exam is done as conventional written text, the influence if the lecture is digital or conventional is weak. Also, the numbers of passing students or the finally achieved mark are mainly not dependent on the type of lecture format. Finally, it can be state that a digital lecture is more successful if there are also digital parts in the examination. Also, the return to conventional lectures and exams after the pandemic period is possible without influencing the student performance compared to pre-pandemic situation

Textile study courses – evaluation of student performance over one complete decade

The success of students and their performance are influenced by manifold parameters. The current study focusses especially on the correlation between study duration and the student performance. Investigated are the numbers of two textile related courses (bachelor and master) over the complete time frame of one decade. Data of more than 800 students are considered. Data evaluation is done with the final marks of the students and by using a calculated value – the student performance index PI. Especially discussed is the behavior of long-time students needing more than the double of the regular study duration. In this study only results of students are discussed which successfully finished the study course with a degree. Students leaving without a degree are not considered. For the bachelor course a correlation of their final grades with larger study duration can be determined. In contrast, for the master course nearly no influence of the study duration on the student performance is determined. A possible explanation for these different results can be discussed with the different reasons for longer study duration. For master course it is obviously the situation that the studying is combined with part-time or even full-time jobs. This combination of job and study course leads even for excellent students to prolonged study duration. With this background, for future developments a special designed part time master study course should be developed and offered for students who like the combination of a job carrier with gaining simultaneously a master degree

Conversion of a conventional to a digital lecture under the conditions of Covid19 – an example from a bachelor lecture on finishing, dyeing & printing

Due to the Covid-19 pandemic situation during the years 2020 and 2021, the necessity occurred to convert conventional university lectures into digital ones, to avoid personal contacts between people and by this minimizing the spreading of the disease. Beside lectures, also exams have to be transferred to minimize personal contacts. This paper reports on a lecture in a bachelor course with more than 100 students and its conversion to digital format. The lecture is related to textile finishing processes – especially to dyeing and printing. The experience get during the digital lecture are compared with the results gained during the last decade with the same lecture in conventional style. Main tools of the digital format are video conferences and digital worksheets. Challenging are the contact to students by e-mail and the time management of the students especially during the final digital homework. In conclusion, digital lecture and exam are valuable tools to increase the number of participating students and their success in the exam. These tools could be also used successfully in post-corona times especially for lectures given for experienced students in higher semester

High-Performance Fibres – A Review of Properties and IR-Spectra

High-performance fibres are fibre materials that exhibit at least one extraordinary property compared to conventional fibre materials. That extraordinary property is frequently related to excellent fibre stability against certain influences such as fire, heat, chemicals or light. Also, a high mechanical strength is often a property of high-performance fibres. Nevertheless, it should be noted that high-performance fibres exhibit certain weaknesses in addition to their advantages. This review presents a broad overview of the most important high-performance fibres, with a special emphasis on their chemical structure and related infrared spectra (IR-spectra). The categorization of the fibres according to chemical substance classes was performed to make it easy for the reader to find a fibre of interest. The main categories are polyethylene (PE) fibres, polyacrylonitrile (PAN) fibres, polyvinylalcohol (PVAL) fibres, polyester-based fibres, polyamide-based fibres, polyetheretherketone (PEEK) fibres, polyimide (PI) fibres, halogen-containing fibres, polyphenylene sulfide (PPS fibres), resin-based fibres and finally inorganic fibres. Competing materials are also discussed, and structural related materials can be easily identified. In addition to discussing fibre properties and selected applications, one of the main aims is to present a various number of IR-spectra as a tool for structural understanding and to help identify unknown fibres. Here, beside the IR-spectra of high-performance fibres, the reference IR-spectra of common fibres are presented for comparison

Treatment of Kynol fiber materials – Part 1: dyeing processes

Kynol fibers are excellent flame-retardant materials used for manifold applications. These fibers exhibit originally an orange coloration. Up to now, dyeing processes for Kynol fibers are less reported, and the functionalization of these fibers by finishing processes is less investigated. With this background, the main aim of this paper is the evaluation of different dyeing processes for Kynol fiber materials – a woven fabric and a non-woven material. The following types of dyestuff are evaluated – direct dyes, vat dyes, disperse dyes and color pigments. The reached color quality is determined by CIE L*a*b* indices. Dry and wet rubbing fastness is measured. Finally, best results are gained by application of disperse dyes. The gained results could be used in future also to develop other functional treatments of Kynol fibers in different fields for, e.g., light protection, UV-stability, water repellency or antistatic properties