K. De Clerck

Analysing the potential of the selective dissolution of elastane from mixed fiber textile waste

K.T. Phan, S. Ügdüler, L. Harinck, R. Denolf, M. Roosen, G. O'Rourke, D. De Vos, V. Van Speybroeck, K. De Clerck, S. De Meester
Resources Conservation and Recycling
191, 106903
2023
A1

Abstract 

Textile products are composed of various blends of synthetic or natural polymers. Elastane increases the functionality during use phase, but impedes high quality recycling. This study investigates the selective chemical dissolution of elastane from blended textile. Hansen solubility parameters and COSMO-RS were applied for solvent screening. The most recommended biobased solvents were experimentally validated with polyester, polyamide, cotton, wool and elastane for which solubility limits were determined and hence, their selectivity towards elastane dissolution. A TGA-corrected gravimetric method was developed as quantification tool and showed that tetrahydrofurfuryl alcohol and ɣ-valerolactone have comparable elastane dissolution capabilities to classical solvents (5 mg elastane/g solvent). Polyester/elastane and polyamide/elastane blends were subjected to this process as case studies. The LCA study showed that this selective solvent-based dissolution process saves 60% CO2-eq./kg textile waste compared to incineration. This interdisciplinary work can set the benchmark for further developing and upscaling physical/dissolution recycling processes for blended textiles.

Green Open Access

Stable Amorphous Solid Dispersion of Flubendazole with High Drug Loading via Solvent Electrospinning

J. Becelaere, E. Van den Broeck, E. Schoolaert, V. Vanhoorne, J. F.R. Van Guyse, M. Vergaelen, S. Borgmans, K. Creemers, V. Van Speybroeck, C. Vervaet, R. Hoogenboom, K. De Clerck
Journal of controlled release
351, November 2022, Pages 123-126
2022
A1

Abstract 

In this work, an important step is taken towards the bioavailability improvement of poorly water-soluble drugs, such as flubendazole (Flu), posing a challenge in the current development of many novel oral-administrable therapeutics. Solvent electrospinning of a solution of the drug and poly(2-ethyl-2-oxazoline) is demonstrated to be a viable strategy to produce stable nanofibrous amorphous solid dispersions (ASDs) with ultrahigh drug-loadings (up to 55 wt% Flu) and long-term stability (at least one year). Importantly, at such high drug loadings, the concentration of the polymer in the electrospinning solution has to be lowered below the concentration where it can be spun in absence of the drug as the interactions between the polymer and the drug result in increased solution viscosity. A combination of experimental analysis and molecular dynamics simulations revealed that this formulation strategy provides strong, dominant and highly stable hydrogen bonds between the polymer and the drug, which is crucial to obtain the high drug-loadings and to preserve the long-term amorphous character of the ASDs upon storage. In vitro drug release studies confirm the remarkable potential of this electrospinning formulation strategy by significantly increased drug solubility values and dissolution rates (respectively tripled and quadrupled compared to the crystalline drug), even after storing the formulation for one year.

A comparative theoretical study on the solvent dependency of anthocyanin extraction profiles

K.T. Phan, E. Van den Broeck, K. Raes, K. De Clerck, V. Van Speybroeck, S. De Meester
Journal of Molecular Liquids
351
2022
A1

Abstract 

Anthocyanidins and anthocyanins are flavonoids with nutritional, antioxidative and color properties that are present in various food products and biomass, such as food waste. The large chemical diversity amongst these molecules potentially leads to different affinities or activities in food and non-food applications. In order to characterize the extraction profile, advanced analytical techniques along with optimized separation procedures are required. Alternatively, theoretical tools can be applied for predicting the solubility or binding affinity of molecules in various reaction media. In this paper, the solubility of anthocyanidins and anthocyanins was analyzed by various theoretical tools such as group contribution methods (e.g., Hansen solubility parameters and Flory-Huggins interaction parameter (χ12)) and molecular modeling (e.g., static calculations based on Density Functional Theory (DFT) and COSMO-RS). It was found that COSMO-RS was able to give quantitative information on the solubility behavior within various pure solvents and it is able to describe the main intermolecular interactions between colorant and solvent, while Hansen solubility parameters were most appropriate to find the most optimal organic solvent-water mixture ratio. In general, solvents with electron-rich aromatic rings and/or containing electron donors, acting as hydrogen bond acceptors, showed the highest solubilizing power for anthocyanidins and anthocyanins.

Gold Open Access

Non-food applications of natural dyes extracted from agro-food residues: A critical review

K.T. Phan, K. Raes, V. Van Speybroeck, M. Roosen, K. De Clerck, S. De Meester
Journal of Cleaner Production
126920
2021
A1

Abstract 

Fruit and vegetables contain molecules that have particular colors, which can potentially be an environmentally attractive substitute for their synthetic counterparts in (non )food applications. The most sustainable source for such natural colorants would be by the valorization of by-products from the fruit and vegetable industries, but qualitative and quantitative characteristics of food by-products for this purpose remain scarce. Natural dyes also show mediocre stability and affinity toward textile fibers, which questions their potential feasibility for application and level of sustainability to overcome these issues. This review describes three dye classes (i.e., anthocyanins, quinones, and carotenoids) along with their occurrence, mass, and concentration in by-products that are generated from agricultural losses as well as the fruit and vegetable processing industries. To tackle the shortcomings of natural dyes on fibers, several application techniques were collected from the literature. A discussion on techno-economic potential and environmental sustainability is included. The latter is done by including a life cycle assessment (LCA) to investigate the environmental impact of extracting anthocyanins, quinones, and carotenoids from fruit and vegetable processing by-products and their subsequent application to the dyeing process. The mapping of by-products for each natural dye class illustrates the vast availability of agro-food residues (>0.1 Mt annually in the EU-28) with a natural dye content of up to 56 kg/t DW for anthocyanins, 18 kg/t DW for quinones, and 593 kg/t DW for carotenoids. Metallic mordants are mostly favored for improving the fixation of natural dyes but entail potential environmental issues. Greener approaches, such as biomordants and enzymes, still show room for improvement, chemical modification methods might also guarantee dye fixation, though questionable in environmental sustainability. The different valorization scenarios of anthocyanins, quinones, and carotenoids from food waste, analyzed with LCA, showed the environmental competitiveness of these natural dyes, applied as a crude extract, compared to synthetic dyes. The valorization routes design shows that agricultural losses and food processing waste streams are adequate sources of natural dyes, especially to be applied in niche scale applications.

A comparative study on the photophysical properties of anthocyanins and pyranoanthocyanins

K.T. Phan, S. De Meester, K. Raes, K. De Clerck, V. Van Speybroeck
Chemistry - A European Journal
27 (19), 5956-5971
2021
A1

Abstract 

Anthocyanins and pyranoanthocyanins are flavonoids that are present in various food products (e.g. fruit, vegetables, wine, etc.). The large chemical diversity amongst these molecules leads to compound specific properties such as color and stability towards external conditions. These properties are also attractive for food and non‐food applications. The photophysical experimental characterization is not easy as this generally demands advanced analytical techniques along with optimized separation procedures. Molecular modeling can provide insights into the fundamental understanding of the photophysical properties of these compounds in a uniform way for a broad set of compounds. However, the current literature is quite fragmented on this topic. Herein, a large set of 140 naturally derived anthocyanins was evaluated in a systematic way with three functionals (B3LYP, PBE0 and CAM‐B3LYP). The accuracy of these functionals was determined with experimental literature λ max,vis ‐values. Next to λ max,vis ‐values, TD‐DFT calculations also provided oscillator strengths, molar absorption coefficients and orbital energies, which define whether specific natural anthocyanin‐based compounds can be deployed in food and non‐food applications such as food additives/colorants, textile dyeing, analytical standards and dye sensitized solar cells (DSSCs).

The potential of anthocyanins from blueberries as a natural dye for cotton: A combined experimental and theoretical study

K.T. Phan, E. Van den Broeck, V. Van Speybroeck, K. De Clerck, K. Raes, S. De Meester
Dyes and Pigments
176, 108180
2020
A1

Abstract 

Natural dyes might be more environmentally sustainable compared to their synthetic counterparts, however in general their performance is worse. Therefore, typically metallic mordants are applied to improve the natural dye's affinity towards substrates, but this is not a suitable technique in a ‘green story’. In this paper, we test the potential of using anthocyanins from blueberry waste for dyeing cotton with biomordants, which are selected to tailor the intermolecular interactions such as hydrogen bonds, ionic bonds and π-π interactions with the dye molecule. In the experimental part, parameters during extraction and dyeing were optimized (e.g. temperature, pH, dyeing time and concentration). The effect of the (bio)mordants was monitored by Fourier transform infrared spectroscopy, spectrophotometric measurements and standard ISO wash and light tests. It was shown that stannous chloride stands out as metallic mordant, while no biomordants show sufficient intermolecular interactions to replace this metal salt. The experimental study has been corroborated with a series of molecular modeling calculations to obtain more insight into the intermolecular interactions between dye and (bio)mordants. To this end, both static Density Functional Theory based calculations as semi-empirical and force field based molecular dynamics calculations have been performed. The results indeed confirm that, in general, too small interaction energies for the biomordants of interest with the dye molecules are found, in correspondence with experimental findings. Overall, by performing systematic experiments in combination with the interpretation of the molecular models, this study yields valuable insights into the development of green routes towards use of anthocyanins as a natural dye for cellulose-based materials.

Open Access version available at UGent repository

Acidity constant (pKa) calculation of large solvated dye molecules: evaluation of two advanced molecular dynamics methods

T. De Meyer, B. Ensing, S.M.J. Rogge, K. De Clerck, E.J. Meijer, V. Van Speybroeck
ChemPhysChem
17 (21), 3447–3459
2016
A1

Abstract 

pH-sensitive dyes are increasingly applied onto polymer substrates for the creation of novel sensor materials. Recently, these dye molecules have been modified to form a covalent bond with the polymer host. This can have a large influence on the pH-sensitive properties, in particular on the acidity constant (pKa). Obtaining molecular control over the factors that influence the pK$_a$ value is mandatory for future intelligent design of sensor materials. Herein, we show that advanced molecular dynamics (MD) methods have reached the level where pKa values of large solvated dye molecules can be predicted with high accuracy. Two MD methods are used in this work: steered or restrained MD and the insertion/deletion scheme. Both are first calibrated on a set of phenol derivatives and afterwards applied to the dye molecule Bromothymol Blue. Excellent agreement with experimental values is obtained, which opens perspectives for using these methods for designing dye molecules.

Open Access version available at UGent repository

Halochromic properties of sulfonphthaleine dyes in a textile environment: the influence of substituents

T. De Meyer, I. Steyaert, K. Hemelsoet, R. Hoogenboom, V. Van Speybroeck, K. De Clerck
Dyes and Pigments
124 (2016), 249-257
2016
A1

Abstract 

The application of pH-sensitive dye molecules onto textile materials is a promising method for the development of sensor materials. Ten commonly used pH-indicators, namely sulfonphthaleine dyes, are applied onto polyamide 6 using two distinct methods: conventional dyeing of fabrics and dye-doping of nanofibres. The influence of the substituents of each dye on their interaction with polyamide, as well as the difference between both application methods is investigated. For the conventionally dyed fabrics, halogen substituents are needed to result in a pH-sensitive fabric. This can be traced back to halogen bonding and is supported by theoretical simulations. Dye-doped nanofibrous non-wovens show significant dye leaching, which can be understood based on the very acidic electrospinning solution. The use of a complexing agent improves the leaching properties, especially for dyes containing four bromine substituents. These findings indicate the importance of halogen substituents on sulfonphthaleines for further research in the development of pH-sensitive sensors.

Open Access version available at UGent repository

Exploring the Vibrational Fingerprint of the Electronic Excitation Energy via Molecular Dynamics

A. Van Yperen-De Deyne, T. De Meyer, E. Pauwels, A. Ghysels, K. De Clerck, M. Waroquier, V. Van Speybroeck, K. Hemelsoet
Journal of Chemical Physics
140 (2014), 134105
2014
A1

Abstract 

A Fourier-based method is presented to relate changes of the molecular structure during a molecular dynamics simulation with fluctuations in the electronic excitation energy. The method implies sampling of the ground state potential energy surface. Subsequently, the power spectrum of the velocities is compared with the power spectrum of the excitation energy computed using time-dependent density functional theory. Peaks in both spectra are compared, and motions exhibiting a linear or quadratic behavior can be distinguished. The quadratically active motions are mainly responsible for the changes in the excitation energy and hence cause shifts between the dynamic and static values of the spectral property. Moreover, information about the potential energy surface of various excited states can be obtained. The procedure is illustrated with three case studies. The first electronic excitation is explored in detail and dominant vibrational motions responsible for changes in the excitation energy are identified for ethylene, biphenyl, and hexamethylbenzene. The proposed method is also extended to other low-energy excitations. Finally, the vibrational fingerprint of the excitation energy of a more complex molecule, in particular the azo dye ethyl orange in a water environment, is analyzed.

Substituent effects on absorption spectra of pH-indicators: An experimental and computational study of sulfonphthaleine dyes

T. De Meyer, K. Hemelsoet, V. Van Speybroeck, K. De Clerck
Dyes and Pigments
102, 241-250
2014
A1

Abstract 

Sulfonphthaleine dyes are an important class of pH indicators, finding applications in novel (textile) sensors. In this paper, we present a combined experimental and theoretical study to elucidate the halochromic behaviour of a large set of sulfonphthaleine compounds. Starting from an experimental analysis consisting of UV/Vis spectroscopy, the pH region and the absorption wavelengths related to the colour shift are obtained and pKa values are derived. The effect of the substituents on the pH region can be traced back to their electron donating/withdrawing properties. Time-Dependent Density Functional Theory (TD-DFT) is able to adequately produce the trend in experimental wavelengths. Proton affinities are used to assess the effect of substituents on the pH region. The combination of theory and experiment is able to give a better understanding of the pH sensitivity; the methodology in this work will be useful in future dye design and is applicable to other dye classes as well.

Open Access version available at UGent repository

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