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128 results on '"Posselt, Dorthe"'

3. Solvothermal vapor annealing setup for thin film treatment: A compact design with in situ solvent vapor concentration probe.

Author

Ariaee, Sina, Jakobsen, Bo, Pedersen, Ib Høst, Rasmussen, Torben Steen, and Posselt, Dorthe

Subjects
THIN films, GAS mixtures, POLYMER films, VAPORS, WASTE gases, SOLVENTS, ACETONE, TOLUENE
Abstract

A compact setup for in situ solvothermal vapor annealing of thin polymer films in the temperature range from room temperature to 70 °C is presented. The design is optimized to avoid solvent condensation in tubes and other components. The setup consists of a chamber, a gas delivery system, a commercial film-thickness measuring device, and a solvent vapor concentration sensor. The chamber is equipped with heaters and thermometers and is thermally insulated. It has windows to allow for penetration of xrays together with a sample table with a gas distributer to ensure homogeneous swelling of the polymer film. The computer-controlled gas delivery system has two different components, which can be used separately or in parallel (for mixed gas solvent annealing): (a) mass flow controllers and a bubbler system and (b) a commercial "controlled evaporation and mixing" system. The film-swelling ratio is determined in situ using optical reflectometry, and the solvent concentration in the exhaust gas is continuously monitored by UV-absorption. Test results are presented where the setup is used for swelling of ∼100 nm thick polystyrene and polyisoprene homopolymer films with toluene and acetone, respectively. [ABSTRACT FROM AUTHOR]

Published
2023
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6. Highly Tunable Nanostructures in a Doubly pH‐Responsive Pentablock Terpolymer in Solution and in Thin Films

Author

Jung, Florian A., primary, Schart, Maximilian, additional, Bührend, Lukas, additional, Meidinger, Elisabeth, additional, Kang, Jia‐Jhen, additional, Niebuur, Bart‐Jan, additional, Ariaee, Sina, additional, Molodenskiy, Dmitry S., additional, Posselt, Dorthe, additional, Amenitsch, Heinz, additional, Tsitsilianis, Constantinos, additional, and Papadakis, Christine M., additional

Published
2021
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14. The dynamics of symmetric polystyrene–polybutadiene diblock copolymer melts studied above and below the order–disorder transition using dynamic light scattering.

Author

Papadakis, Christine M., Brown, Wyn, Johnsen, Robert M., Posselt, Dorthe, and Almdal, Kristoffer

Subjects
DYNAMICS, COPOLYMERS, LIGHT scattering
Abstract

This communication describes dynamic light scattering measurements on three low molar mass symmetric polystyrene–polybutadiene diblock copolymer melts. Above but close to the order–disorder transition, four modes contribute to the time-dependent correlation function. In the depolarized geometry there is a very fast, broad relaxation typifying the segmental reorientational dynamics and a slower, single-exponential mode related to chain orientation and stretching. In the polarized experiments two additional processes are seen: the heterogeneity mode related to the self-diffusion of individual copolymer molecules and a slow mode representing the translational diffusion of large ([bar_over_tilde:_approx._equal_to]100 nm) clusters. Just below the order–disorder transition (ODT), the slowest mode is shifted to very long times. The heterogeneity mode gives rise to depolarized scattering below the ODT because of the anisotropy induced by the lamellar structure. With the lowest molar mass copolymer above the ODT, it could be seen that the amplitude of the mode related to chain orientation and stretching decreases the deeper the sample is in the disordered state. A new subtraction technique was used for data analysis. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Published
1996
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20. Optimization of a multi-parameter model for biomass pelletization to investigate temperature dependence and to facilitate fast testing of pelletization behavior

Author

Holm, Jens Kai, Stelte, Wolfgang, Posselt, Dorthe, Ahrenfeldt, Jesper, Henriksen, Ulrik Birk, Holm, Jens Kai, Stelte, Wolfgang, Posselt, Dorthe, Ahrenfeldt, Jesper, and Henriksen, Ulrik Birk

Abstract

Pelletization of biomass residues increases the energy density, reduces storage and transportation costs and results in a homogeneous product with well-defined physical properties. However, raw materials for fuel pellet production consist of ligno-cellulosic biomass from various resources and are therefore different in their composition and structural properties. This has the consequence that different types of biomass require different processing conditions such as press channel length and moisture content. Nowadays the process optimization is mainly based on expensive and time consuming “trial and error” experiments and personal experience. However in recent years the utilization of single pellet press units for testing the biomass pelletizing properties has attracted more attention. The present study outlines an approach where single pellet press testing is combined with modeling to mimic the pelletizing behavior of new types of biomass in a large scale pellet mill. This enables a fast estimation of key process parameters such as optimal press channel length and moisture content. Secondly, the study addresses the question of the origin of the observed relationship between pelletizing pressure and temperature.

Published
2011

21. Fundamental Understanding of Pelletization:EFP-2005 project (33031-037)

Author

Møller, Jette Dahl, Henriksen, Ulrik B, Holm, Jens Kaj, Simonsen, Peter, Berg, Mogens, Posselt, Dorthe, Nicolaisen, Lars, Plackett, David, Møller, Jette Dahl, Henriksen, Ulrik B, Holm, Jens Kaj, Simonsen, Peter, Berg, Mogens, Posselt, Dorthe, Nicolaisen, Lars, and Plackett, David

Published
2008

22. Macromol. Rapid Commun. 16/2013

Author

Zhang, Jianqi, primary, Posselt, Dorthe, additional, Sepe, Alessandro, additional, Shen, Xuhu, additional, Perlich, Jan, additional, Smilgies, Detlef-M., additional, and Papadakis, Christine M., additional

Published
2013
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26. Small-angle neutron scattering study of the ultrastructure of chloroplast thylakoid membranes — Periodicity and structural flexibility of the stroma lamellae

Author

Posselt, Dorthe, primary, Nagy, Gergely, additional, Kirkensgaard, Jacob J.K., additional, Holm, Jens K., additional, Aagaard, Thomas H., additional, Timmins, Peter, additional, Rétfalvi, Eszter, additional, Rosta, László, additional, Kovács, László, additional, and Garab, Győző, additional

Published
2012
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35. Macromol. Rapid Commun. 5/2007

Author

Potemkin, Igor I., primary, Busch, Peter, additional, Smilgies, Detlef-M., additional, Posselt, Dorthe, additional, and Papadakis, Christine M., additional

Published
2007
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39. Lamellar Diblock Copolymer Thin Films during SolventVapor Annealing Studied by GISAXS: Different Behavior of Paralleland Perpendicular Lamellae.

Author

Zhang, Jianqi, Posselt, Dorthe, Smilgies, Detlef-M., Perlich, Jan, Kyriakos, Konstantinos, Jaksch, Sebastian, and Papadakis, Christine M.

Subjects
*DIBLOCK copolymers, *THIN films, *SOLVENTS, *ANNEALING of crystals, *X-ray scattering, *ANNEALING of metals
Abstract

The reorientation of lamellae andthe dependence of the lamellarspacing, Dlam, on polymer volume fraction,ϕP, Dlam∝ ϕP–β, in diblock copolymer thin films during solvent vapor annealing(SVA) are examined by combining white light interferometry (WLI) andgrazing-incidence small-angle X-ray scattering (GISAXS). A thin filmof lamellae-forming poly(styrene-b-butadiene) preparedby spin-coating features lamellae of different orientations with thelamellar spacing depending on orientation. During annealing with ethylacetate (EAC) vapor, it is found that perpendicular lamellae behavedifferently from parallel ones, which is due to the fact that theirinitial lamellar thicknesses differ strongly. Quantitatively, theswelling process is composed of three regimes and the drying processof two regimes. The first two regimes of swelling are associated witha significant structural rearrangement of the lamellae; i.e., thelamellae first become thicker, and then perpendicular and randomlyoriented lamellae vanish, which results in a purely parallel orientationat the end of the swelling process. The rearrangement is attributedto the increase of mobility of the polymer chains imparted by thesolvent and to a decrease of total free energy of the thin film. Inthe third regime of swelling, the scaling exponent is found to beβ = −0.32. During drying, the deswelling is nonaffinewhich may be a consequence of the increase of nonfavorable segmentalinteractions as the solvent is removed. [ABSTRACT FROM AUTHOR]

Published
2014
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46. Stepwise Swelling of aThin Film of Lamellae-Forming Poly(styrene-b-butadiene)in Cyclohexane Vapor.

Author

Di, Zhenyu, Posselt, Dorthe, Smilgies, Detlef-M., Li, Ruipeng, Rauscher, Markus, Potemkin, Igor I., and Papadakis, Christine M.

Subjects
*THIN films, *POLYSTYRENE, *BUTADIENE, *CYCLOHEXANE, *X-ray scattering, *THERMOPLASTICS, *VAPORS, *SWELLING of materials
Abstract

We investigated the swelling of a thin film of lamellae-formingpoly(styrene-b-butadiene) in cyclohexane vapor. Thevapor pressure and thus the degree of swelling of the film are increasedin a stepwise manner using a custom-built sample cell. The resultingstructural changes during and after each step were followed in situusing time-resolved grazing-incidence small-angle X-ray scattering(GISAXS). During the first step, the lamellar thickness increasesstrongly, before it decreases again. At the same time, the full widthat half-maximum (FWHM) of the diffuse Bragg reflection along the filmnormal has a sharp maximum. These observations point to the formationof new lamellae. During the subsequent swelling steps, the lamellarthickness overshoots only weakly. The behavior thus resembles qualitativelyour previous results on a similar thin film during swelling in saturatedvapor of cyclohexane; however, it deviates from earlier theoreticalpredictions. We propose a theory that is quantitatively correct forthe description of the dependence of the lamellar thickness on thepolymer volume fraction in the late stage of the swelling steps. [ABSTRACT FROM AUTHOR]

Published
2012
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48. Study of Swelling Response Variation in Homopolymer Thin Films during SVA

Author

Gow, Jonathan Michael and Posselt, Dorthe

Abstract

The goal of this project is to find relationships between the properties of homopolymer thin films and the swelling behavior of the films during Solvent Vapor Annealing (SVA). Solvent sorption and desorption in thin films is governed by interaction parameters which are not well determined. Testing of samples which vary over a single parameter is used to determine their correlation with specific features of swelling behavior.I developed and implemented a simplified program for consistent solvent vapor introduction with precise timings and smooth swelling response for a specific polymer-solvent pair, Polystyrene and Toluene. Evaluation of the program consisted of tests on polymers ranging in molar mass from 1.8 to 6000 kg/mol, and film thicknesses ranging from as low as 40nm up to 260nm. The swelling kinetics and optical properties are recorded as a function of time, and correlated across the range of samples.Features of the swelling response include identification of the Glass Transition, distinct solvent sorption hysteresis around the Glass Transition, variation in the maximum equilibrium swelling position, and early characterization of signs of de-wetting. Also discussed is the effects of thermal annealing prior to SVA.The Fresnel equations describing interfaces of optical media are used to characterize the swelling response, and for qualitative description of the film surface uniformity. The Flory-Huggins model of polymer melts is analyzed and evaluated as a quantitative predictor of thin-film swelling. Deviations from the model are identified, quantified, and given physical interpretations.Iterative development of the annealing procedure and analysis methods has improved reliability and quantified parameters relevant to the methodology that were previously unknown or misunderstood. This includes demonstration of swelling dependent index of refraction for thin films, and solvent concentration dependent index of refraction for the carrier gas.It is found that the polymers show no variation in Glass Transition temperature as a result of being confined to thin film geometries in this thickness range. While maximum swelling ratio of the films does vary, it does not show correlation with the thickness.It is found that the Glass Transition temperature of polymers as a function of their molar mass is not affected by being constrained to a thin film. The same functional relationship to the Fox equation is maintained for all samples.

Published
2023

50. Extracellular vesicles characterized by dynamic light scattering

Author

Mahler, Frederik Storm, Dalgaard, Louise Torp, and Posselt, Dorthe

Subjects
Ekstracellulære vesikler, dynamisk lysspredning, oprensningsprotokol
Abstract

This study attempts to isolate extracellular vesicles from blood serum frompregnant and non-pregnant women through a protocol using ultracentrifugation. Small extracellular vesicles are reported to be in the size range of30-150nm and are involved in many physiological and pathophysiologicalprocesses. Their exact roles in many of these processes are unclear and theirphysical characteristics still needs further investigations. The prospect of abetter understanding of extracellular vesicles’ function and heterogeneity willcontribute with novel markers for a range of different diseases, along withfurther insight into disease development.The aim of this study is to develop a full protocol to isolate extracellularvesicles into samples that can be characterized with dynamic light scattering. The protocol uses differential centrifugation that can sort out particlesof different sizes according to their sedimentation speeds. This is followed bycentrifugation through a discontinuous sucrose gradient where the particlesare spatially separated by their differences in densities. Dynamic light scattering is a non-invasive technique which enables measurements of sampleswithout harming the content. Dynamic light scattering measures intensitiesof light scattered by particles moving with Brownian motions in suspensionsand correlate the dynamic signals to derive size distributions of the particles.This study found that the developed protocol separates small extracellular vesicles where only a few samples are purified enough for characterizationwith dynamic light scattering. The best purified samples show sizes distributions ranging from 10-50nm, which is smaller than earlier reported sizesfor small extracellular vesicles. Further identification of the exact content ofthese samples are needed.

Published
2021

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