Alina Adams Buda

Alina Adams Buda
RWTH Aachen University · Institute for Technical und Macromolecular Chemistry

PD Dr. Interim Professor

About

66
Publications
6,204
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1,042
Citations
Additional affiliations
April 2001 - present
RWTH Aachen University
Position
  • Group Leader

Publications

Publications (66)
Article
Natural gas is an essential energy source for a large variety of applications in today’s society. Forecasts predict that it will also play a vital role in decarbonizing the energy sector. The price of natural gas is determined by its calorific value, which depends on its composition. Thus, the accurate composition quantification of natural gas is e...
Preprint
Full-text available
The spatial resolution of magnetic resonance imaging (MRI) is fundamentally limited by the width of Lorentzian point spread functions (PSF) associated with the exponential decay rate of transverse magnetization (1/T2*). Here we show a different contrast mechanism in MRI by establishing RASER (Radio-frequency Amplification by Stimulated Emission of...
Article
Leather artefacts, archaeological, historical or modern, are prone to microbiological attack which could lead to irreversible degradation. Previous studies performed on new leather mock-ups indicated good resistance of leather at doses up to (25–50) kGy. The aim of this research is to improve our understanding about the changes in the thermal stabi...
Article
Full-text available
Metal–organic frameworks (MOFs) have great potential as an efficient alternative to current separation and purification procedures of a large variety of solvent mixtures—a critical process in many applications. Due to the huge number of existing MOFs, it is of key importance to identify high-throughput analytical tools, which can be used for their...
Article
A simple, yet highly versatile setup is presented for benchtop NMR analyses of gases at high-pressure. It consists mostly of commercial parts and includes multiple safety features while maintaining a small size to fit into a 1.20 m wide fume hood. Pressures up to 200 bar can be adjusted independently of the sample gas-bottle pressure in a matter of...
Article
Full-text available
Polyvinyl chloride (PVC), one of the most important polymer materials nowadays, has a large variety of formulations through the addition of various plasticizers to meet the property requirements of the different fields of applications. Routine analytical methods able to identify plasticizers and quantify their amount inside a PVC product with a hig...
Article
Heizöl und Dieselkraftstoff mit höheren Fettsäuremethylesteranteilen aus regenerativen Quellen verhalten sich im Betrieb und bei der Lagerung anders als bisher üblich. Betriebsstörungen von Motoren und Ölheizungen lassen sich durch Additive in den Brennstoffmischungen vermeiden.
Article
Low-field nuclear magnetic resonance (NMR) based on permanent magnet technologies is currently experiencing a considerable growth of popularity in studying polymer materials. Various bulk properties can be probed with compact NMR tabletop instruments by placing the sample of interest inside the magnet. Contrary to this, compact NMR sensors with ope...
Article
Today many polyethylene (PE) products are employed in long‐term applications that require the use of elevated temperatures and/or contact with different solvents. Both the exposure to heat and solvents can result in morphological changes, compromising the mechanical stability of the material. Disentangling morphological changes induced by either ty...
Article
Poly(vinyl chloride) (PVC) is today one of the most important commodity polymers. Its broad range of applications is due to the presence of plasticizers whose concentration largely impacts the microscopic and the macroscopic properties. Quantifying the concentration of plasticizer in PVC products is therefore of fundamental importance. Thus, in thi...
Article
The changes in the structure and dynamics of collagen treated with two different classes of ionic liquids, bis-choline sulphate (CS) and 1-butyl-3-methyl imidazolium dimethyl phosphate (IDP) have been studied at the molecular and fibrillar levels. At molecular level, circular dichroic studies revealed an increase in molar ellipticity values for CS...
Article
Full-text available
New and artificially aged parchments were studied by unilateral NMR and micro DSC. Samples were obtained by exposing new parchments to 80 °C and alternate 40 and 80% relative humidity for increasing times up to 32 days. The impact of accelerated ageing was assessed by measuring both the proton transverse relaxation times (T2eff) and thermodynamic p...
Article
The synthesis of borazine-based hybrid cyclomatrix polymers has been studied under various conditions. Crosslinked polymers obtained via a novel silicon/boron exchange precipitation polycondensation approach form hybrid cyclomatrix microspheres with a...
Article
A protocol for the fast and selective two-electron reduction of the potent greenhouse gas sulfur hexafluoride (SF6) by organic electron donors at ambient temperature has been developed. The reaction yields solid ion pairs consisting of donor dications and SF5-anions which can be effectively used in fluorination reactions.
Article
A radio-frequency coil with adjustable distance has been developed and tested for in-situ examination of growing plants. The Helmholtz-based coil design reduces laborious tuning and matching efforts encountered with solenoids wound around a growing stem or branch. Relaxation experiments were performed on tomato plants and winter wheat under control...
Article
It is accepted knowledge that solvents diffuse in the amorphous phase of semi-crystalline polymers. Yet these solvents may trigger swelling that affects segmental chain mobility and gives rise to changes of the polymer. This study explores compact low-field NMR as a fast, simple, and low-cost method of analysis to detect such swelling-induced morph...
Article
Nuclear magnetic resonance (NMR) is today one of the most important analytical tools for the detailed characterization of solid polymers at various length and time scales. Such information is key for establishing proper structure-property relationships required for the rational design of polymers for particular applications. Several microscopic pro...
Article
Full-text available
Unilateral nuclear magnetic resonance (NMR) and imaging thermal microscopy (imageMHT) were performed on newly obtained and artificially aged vegetable tanned leathers. Calf and sheep leathers tanned with vegetal extracts of mimosa bark, quebracho and chestnut wood were compared. Ageing was simulated by exposing the leather samples to heating at 70...
Article
The properties of plasticized poly(vinyl chloride) (PVC) , one of the most important polymers today, are strongly dictated by the concentration of plasticizer. Yet, it has been impossible to quantify this concentration at different positions inside a PVC product without its destruction because of a lack of suitable analytical methods. Thus, this pa...
Article
The potential of single-sided Nuclear Magnetic Resonance (NMR) to monitor truly non-invasive changes in polymer materials during aging under aggressive media is for the first time evaluated. For this, the NMR method is used in combination with other condition monitoring methods including mechanical measurements, mass uptake, and differential scanni...
Article
Ruthenium nanoparticles were immobilized onto an acidic supported ionic liquid phase (RuNPs@SILP) in the development of bifunctional catalysts for the selective deoxygenation of biomass substrates. RuNPs@SILPs possessed high catalytic activities, selectivities and recyclabilities in the hydrogenolytic deoxygenation and ring opening of C8- and C9-su...
Article
We report nuclear magnetic resonance (NMR) results on water saturated, dense, nano-crystalline YSZ samples (9.5 mol% yttria doped zirconia) which exhibit proton conductivity at temperatures as low as room temperature. (1)H-NMR spectra recorded under static and magic angle spinning conditions show two distinct signals. Their temperature-dependent be...
Article
The incorporation process of a defined (13)C- and (14)C-labeled nonylphenol isomer (4-(3,5-dimethylhept-3-yl)phenol) into soil derived organo-clay complexes was investigated. Isolated organo-clay complexes were separated into humic sub-fractions. Non-invasive ((13)C-CP/MAS NMR) as well as invasive methods (sequential chemical degradation, pyrolysis...
Article
Morphological changes of large-size semicrystalline polyethylene samples induced by different procedures such as annealing, aging, deformation, and interaction with solvents have been investigated non-destructively by single-sided NMR. The results are summarized and problems encountered in the characterisation of these polymer materials and the opp...
Article
The hydration of recently developed cement-in-polymer dispersions (c/p) containing 30% and 40% poly(vinyl acetate) [PVAc] and 30% poly(vinyl alcohol) [PVA] was monitored on-line at various temperatures using 1H Single Point Imaging (SPI). The physical changes undergone by the materials as well as the complex manner in which the absorption process t...
Article
A simple and fast way to measure proton self-diffusion coefficients of small penetrant molecules in semicrystalline polymers is introduced. The approach takes advantage of the strong static gradient of a mobile single-sided NMR sensor and it is demonstrated on PE samples with varying degrees of crystallinity fully saturated in either toluene or n-h...
Article
The behaviour of two novel cement-in-polymer (c/p) dispersions, namely cement-in-poly(vinyl acetate) and cement-in-poly(vinyl alcohol) upon exposure to water at room temperature was investigated by a combination of various NMR methods. The swelling, cracking, and the water ingress were monitored non-destructively using 1H single point imaging. The...
Article
Full-text available
Recently, we reported on soil fate of SDZ residues amended with pig manure treated with ¹⁴C-labeled sulfadiazine ¹⁴C-SDZ). The first objective of the present study was to determine whether this strategy can be substituted by application of ¹⁴C-SDZ to soil. The second objective was to characterize non-extractable SDZ residues by fractionation, size...
Article
Cement-in-polymer (c/p) dispersions allow the full utilisation of the reinforcing abilities of multifilament rovings in concrete. In this work the role of the polymer properties on the performance of the c/p dispersions is investigated and discussed. Two model polymers are chosen and c/p dispersions made with these are investigated regarding the wa...
Article
A naturally occurring clay mineral, palygorskite, which has the microstructure of nano-fibers, was used to support a metallocene compound, Cp2TiCl2. After activation by methylaluminoxane, the supported catalyst initiated an in situ ethylene polymerization resulting in the exfoliated dispersion of the nano-fibers into the polyethylene matrix. With n...
Article
Novel exfoliated polyethylene (PE)/palygorskite nanocomposites prepared by in situ polymerization are characterized by solid-state nuclear magnetic resonance (NMR). The phase structure and molecular mobility are investigated by a combination of proton and carbon NMR. The results showed that incorporation of small amounts of palygorskite had great i...
Article
The morphology of a series of novel segmented PEAs with varying amide content was studied by a combination of DSC, SFM and proton solid state NMR. Semicrystalline polymers organised in a lamellar morphology were obtained for all amide contents. The results of different NMR experiments revealed that a three phase system composed of a rigid phase, an...
Article
Using different ¹H solid-state NMR techniques, the Cr-catalyzed ethylene-hexene copolymer with different hexene content was investigated, and the effects of comonomer content on the phase composition, molecular mobility and domain size of the copolymer were studied. The results showed that the mass fraction of crystalline phase was decreased with t...
Article
The effects of electrospun silicananofiber mats on the tensile and bending strength of epoxy resins, were presented with the influence of pretreatments such as thermal annealing, hydrothermal treatment, and surface functionalization of the mats. The importance of proper annealing conditions was substantiated by tensile tests of reinforced epoxy spe...
Article
Magnetic Resonance (NMR: Nuclear Magnetic Resonance) is known in medical imaging as a diagnostic tool and in chemistry as a spectroscopic method for molecular structural analysis. In both cases, the object of interest is investigated with radio-frequency waves in the center of strong super-conducting magnets. High and homogeneous magnetic fields si...
Article
Full-text available
Molecular mobility, the thickness of domains and the amount of rigid, semi-rigid, and soft fractions of high-density polyethylene (HDPE) were characterized as a function of temperature and annealing time using time- and frequency-domains proton solid-state NMR. These experiments established the temperature range for which the largest differences ar...
Article
The morphology and domain sizes are reported for a series of thermoplastic polyurethane (TPU) samples with different content in hard segments and the same molecular weight of the soft segments. NMR spin-diffusion experiments were employed with a 1H double-quantum dipolar filter to establish the dominant dimensionality of the spin-diffusion process,...
Article
NMR (Nuclear Magnetic Resonance) is established in medicine as a diagnostic tool and in Chemistry as a method for analysis of molecular structures. In either case, the object is investigated with radio-frequency waves in the center of a large magnet. In recent years, new devices like the NMR-Mouse (Mobile Universal Surface Explorer) have been devel...
Article
Hyperbranched polyethoxysiloxanes were prepared via a one-pot synthetic route based on a condensation reaction of tetraethoxysilane with acetic anhydride in the presence of an organotitanium catalyst. Volatile compounds can be fully removed using a thin-film evaporator. According to size-exclusion chromatography and viscosity measurements, the aver...
Article
A survey of recent homo- (H-1) and heteronuclear (C-13-H-1) multiple-quantum (MQ) NMR experiments performed in our group at RWTH-Aachen on soft solids is given. MQ build-up curves are used for measurement of residual van Vleck moments and as dipolar filters in spin-diffusion experiments. The orientation studies were made with the help of MQ edited...
Article
Copolymer networks synthesized from dilactide and diglycolide were characterized by solid-state 13C CPMAS NMR in terms of composition, cross-link density, and rate of cross-linking by UV irradiation. The latter is directly evident by a signal at 44 ppm in the 13C NMR spectrum. Comparison of solid-state NMR data with the determination of the gel con...
Article
Full-text available
NMR relaxometry is a suitable tool to determine the morphology of semi-crystalline polymers by its ability to discriminate between rigid, mostly crystalline and soft, usually amorphous material. The NMR-MOUSE® (nuclear magnetic resonance mobile universal surface explorer) was explored in this work to supply morphological data of poly(ethylene) pipe...
Article
Polymer networks made from oligo[(L-lactide-ran-glycolide)]dimethacrylates by UV curing are characterized by solid-state NMR. These polymer networks show a shape-memory effect and could be used as temporary implant materials for medical applications. The (13)C spectra enable the direct determination of the cross-link density by a signal at 44 ppm....
Article
The dynamics and molecular order of thin lipid (lecithin) films confined to 200, 100 and 20 nm cylindrical pores with varying surface coverage, were investigated by 1H multiple-quantum NMR. The results show that the molecular dynamics in the surface controlled layers are less hindered compared to those in the bulk. Dynamic heterogeneity among termi...
Article
The molecular dynamic heterogeneity of monolayer to submonolayer thin lecithin films confined to submicron cylindrical pores were investigated by 1H magnetization exchange nuclear magnetic resonance. In this experiment a z-magnetization gradient was generated by a double-quantum dipolar filter. The magnetization-exchange decay and buildup curves we...
Article
Polymer networks made from oligo[(L-lactide-ran glycolide)]dimethacrylates by UV curing are characterized by solid-state NMR. These polymer networks show a shape-memory effect and could be used as temporary implant materials for medical applications. The 13C spectra enable the direct determination of the cross-link density by a signal at 44 ppm. Th...
Article
The complex morphology of high-speed melt-spun nylon-6 fibres hydrated with D2O was investigated using 1H double-quantum-filtered spin-diffusion NMR experiments. The magnetisation exchange from selected crystalline domains along the fibrils and interfibrils was simulated with the help of a three-dimensional solution of a spin-diffusion equation app...
Article
1H spin-diffusion experiments employing a double-quantum (DQ) dipolar filter were performed for the characterization of the microdomain structure of heterogeneous samples. For this purpose the NMR spin-diffusion process was analysed based on a model morphology of three different domains with arbitrary sizes, diffusivities, and filter efficiency. Ge...
Article
The NMR spin-diffusion process taking place in a morphology represented by three different domains with arbitrary sizes and diffusivities is investigated. General analytical solutions valid for the full range of spin-diffusion times were obtained for a one-dimensional lamellar morphology. The accuracy of these solutions has been tested by predictin...
Article
The porosity of membranes formed from acrylonitrile-sodium methallylsulfonate copolymer was characterized from the analysis of the depression of the melting point of absorbed water. Membranes were obtained either as a foam or as a hollow fiber; the foam consisted of interconnected macrocavities (mean diameter about equal to 1 mm) while the hollow f...
Article
Full-text available
Ein wichtiges Ziel in der Materialforschung ist das Aufzeigen der Abhängigkeiten der makroskopischen Eigenschaften von den mikroskopisch verteilten Inhomogenitäten innerhalb von Materialen. Diese Information ist wichtig für die Herstellung von Materialien mit bestimmten Eigenschaften. Spin-Diffusions-NMR ist eine etablierte Methode zur Bestimmung d...

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Dear Colleagues, Polymers are nowadays a driving force in our society. Unfortunately, they have a major drawback: independent of the application, they experience changes in their macroscopic properties with time upon the impact of various external factors including temperature, radiation, humidity, and mechanical load. While many researchers conduct accelerated aging studies, the reported results rarely match the observations from the natural aging. The main raisons for this discrepancy are currently attributed to the spatial dependence of the changes with the aging time and the combined effects of various types of aging. The macroscopic properties of polymers are largely determined by their morphology in terms of chemical structure, molecular dynamics, molecular weight, crystallinity degree etc. Thus, understanding and modeling the temporal and the spatial physical and chemical changes in the molecular network will provide the framework for establishing reliable structure-properties relationships requested for a better understanding of the experimental observations and for determining their lifetime. For this, one needs to take advantage of the capabilities of various modern analytical methods, which are able to probe different morphological aspects and to identify the most sensitive microscopic parameters towards aging. Moreover, there is great need for simple, robust, and low-cost analytical methods for onsite non-destructive morphological evaluation. In this way, systematic details about the microscopic changes associated with natural aging can be gained. This special issue aims at collecting research and review articles covering all aspects of aging-induced morphological changes in polymer materials. It provides a platform for discussing challenges and open issues by presenting suitable morphological characterization techniques and modeling methods for improved structure-properties relationships. Interim Professor, Dr. habil. Alina Adams Guest Editor