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Recent Publications


Surface-modified elastomeric nanofluidic devices for single nanoparticle trapping

pfohl-02.jpgOur work focuses on the development of simpler and effective production of nanofluidic devices for high-throughput charged single nanoparticle trapping in an aqueous environment. Single nanoparticle confinement using electrostatic trapping has been an effective approach to study the fundamental properties of charged molecules under a controlled aqueous environment. Conventionally, geometry-induced electrostatic trapping devices are fabricated using SiOx-based substrates and comprise nanochannels imbedded with nanoindentations such as nanopockets, nanoslits and nanogrids. These geometry-induced electrostatic trapping devices can only trap negatively charged particles, and therefore, to trap positively charged particles, modification of the device surface is required. [more...]



Changes in Surface Free Energy and Surface Conductivity of Carbon Nanotube/Polyimide Nanocomposite Films Induced by UV Irradiation

am1c02654_0012.gifChanges in surface energy and electrical conductivity of polyimide (PI)-based nanocomposite films filled with carbon nanotubes (CNTs) induced by UV exposure are gaining considerable interest in microelectronic, aeronautical, and aerospace applications. However, the underlying mechanism of PI photochemistry and oxidation reactions induced by UV irradiation upon the surface in the presence of CNTs is still not clear. Here, we probed the interplay between CNTs and PIs under UV exposure in the surface properties of CNT/PI nanocomposite films.   [more...]


  
Continuous Illumination of a Conjugated Polymer Causes Strong Enhancement of Photoluminescence

jp1c01837_0009.jpgWe present measurements of absorbance and photoluminescence (PL) for films of poly(3-(2,5-dioctylphenyl)thiophene) (PDOPT) as a function of temperature (T) and time (t) of illumination. While having no detectable influence on absorbance of this conjugated polymer, our experiments clearly revealed that illumination of PDOPT caused a significant increase in the PL intensity (IPL(T,t)), that is, the emission probability of PDOPT. Without illumination, we always observed a decrease in IPL with time. An increase in IPL was only detectable when the sample was illuminated. Interestingly, while absorption and emission of photons occur on a time scale of nanoseconds, the here-reported changes in the emission probability were slow and occurred on a time scale of minutes to hours. [more...]



Self-Seeding Procedure for Obtaining Stacked Block Copolymer Lamellar Crystals in Solution

brahim-polymers.jpgWe examined the formation of self-seeded platelet-like crystals from polystyrene-block-polyethylene oxide (PS-b-PEO) diblock copolymers in toluene as a function of polymer concentration (c), crystallization temperature (TC), and self-seeding temperature (TSS). We showed that the number (N) of platelet-like crystals and their mean lateral size (L) can be controlled through a self-seeding procedure. As (homogeneous) nucleation was circumvented by the self-seeding procedure, N did not depend on TC. N increased linearly with c and decayed exponentially with TSS but was not affected significantly by the time the sample was kept at TSS.  [more...]



Formation of Stacked Three-Dimensional Polymer “Single Crystals”

ma1c00081_0006.gif

Stacks of crystalline lamellae all having a uniquely oriented hexagonal shape, referred to as “3D (three-dimensional) single crystals”, were obtained via isothermal crystallization of isotactic polystyrene at a temperature close to the melting point. The height of the stacks of lamellae reached several micrometers corresponding to hundreds of superposed lamellar crystals. We propose that the mechanism of self-induced nucleation allowed propagating the orientation of the basal lamellar crystal to all other lamellae in the stack. [more...]



Concepts of nucleation in polymer crystallization

2021-xujun.jpgNucleation plays a vital role in polymer crystallization, in which chain connectivity and thus the multiple length and time scales make crystal nucleation of polymer chains an interesting but complex subject. Though the topic has been intensively studied in the past decades, there are still many open questions to answer. The final properties of semicrystalline polymer materials are affected by all of the following: the starting melt, paths of nucleation, organization of lamellar crystals and evolution of the final crystalline structures. [more...]



Optimization of Nanofluidic Devices for Geometry‐Induced Electrostatic Trapping

2021-pfo-01c.jpgNanoparticle trapping in a nanofluidic device utilizing geometry-induced electrostatic (GIE) potential trap is an efficient and robust way to perform nano‑object confinement and single particle studies. The GIE‑trapping is a passive method that solely depends on the device geometry and device-particle surface interaction. Therefore, optimization of a nanofluidic device based on experimental requirements, helps to achieve stiffer single-particle trapping. The efficiency of a GIE‑trapping device is defined in terms of residence time and trapping stiffness of the nanoparticle inside a potential trap. The present study reveals all crucial parameters that affect the device efficiency, particle trapping stiffness, and particle residence time. [more...]

 

List of Publications

Crystallization and Melting of Fractions of Branched Polyethylene. 2. Dilatometric and Small-Angle X-Ray-Scattering Study on the Molecular Weight Dependence of Isothermal Crystallization
E. Maderek, G.R. Strobl. Coll. Polym. Sci. 261, 471-476 (1983)
Effect of Amorphous Sequences on the Longitudinal Acoustic Modes in Partially Crystalline Polymers. 1. Transfer Matrix Method
G.R. Strobl. J. Polym. Sci. B - Polymer Physics 21, 1357-1380 (1983)
On the Kinetics of Isothermal Crystallization of Branched Polyethylene
G.R. Strobl, T. Engelke, E. Madarek, G. Urban. Polymer 24, 1585-1589 (1983)
Kristallisation und Schmelzverhalten von Fraktionen verzweigten Polyethylens. 1. Darstellung und Charakterisierung der Fraktionen
Eugeniusz Maderek, Gert R. Strobl. Makromolekulare Chemie - Macromolecular Chemistry and Physics 184, 2553-2561 (1983)
Raman Spectrum of the High Pressure Phase of Polyethylene
R. Eckel, H. Schwickert, M. Buback, G.R. Strobl. Polymer Bulletin 6, 559-564 (1982)
Die Kristallstruktur von Cycloalkanen
Thomas Trzebiatowski, Martin Dräger, Gert R. Strobl. Makromolekulare Chemie - Macromolecular Chemistry and Physics 183, 731-744 (1982)
Zum Mechanismus der Polymerkristallisation
G. R. Strobl, T. Engelke, H. Meier, G. Urban. Coll. Polym. Sci. 260, 394-403 (1982)
Pressure induced changes in the Raman spectra of liquid n-alkanes and perfluoro-n-alkanes
H. Schwickert, G. R. Strobl and R. Eckel. Coll. Polym. Sci. 260, 588-593 (1982)
Untersuchung der druckinduzierten Kristallisation von Polyäthylen mit Hilfe einer neuen Raman-Hochdruckzelle
R. Eckel, M. Buback und G. R. Strobl. Coll. Polym. Sci. 259, 326-334 (1981)
Model of Partial Crystallization and Melting Derived from Small-Angle X-Ray-Scattering and Electron-Microscopic Studies on Low-Density Polyethylene
G.R. Strobl, M.J. Schneider, I.G. Voigt-Martin. J. Polym. Sci. B - Polymer Physics 18, 1361-1381 (1980)
Direct Evaluation of the Electron Density Correlation Function of Partially Crystalline Polymers
G.R. Strobl, M. Schneider. J. Polym. Sci. B - Polymer Physics 18, 1343-1359 (1980)
Analysis of the Intensities of the Longitudinal Acoustic Vibtrations in n-Alkanes and Polyethylene
G.R. Strobl, R. Eckel. Coll. Polym. Sci. 258, 570-577 (1980)
Phase-Transitions in Crystals of Chain Molecules. Relation between Defect Structures and Molecular Motion in the four Modifications of n-C33H68
B. Ewen, G.R. Strobl, D. Richter. Faraday Discussions 69, 19-31 (1980)
Molecular Orientational Correlations and Local Order in n-Alkane Liquids
E.W. Fischer, G.R. Strobl, M. Dettenmaier, M. Stamm, N. Steidle. Faraday Discussions 68, 26-45 (1979)
Einige polymerspezifische Anwendungen der Schwingungsspektroskopie
G.R. Strobl. Coll. Polym. Sci. 257, 584-590 (1979)
Circular Fluorescence Polarization of Achiral Molecules in Cholesteric Liquid Crystals
H. Stegemeyer, W. Stille and P. Pollmann. Israel J. Chem. 18, 312 (1979)
Molekulare Deutung der Umwandlungswärmen bei den Modifikationsübergängen des n-Tritriacontans
G.R. Strobl. Coll. Polym. Sci. 256, 427-445 (1978)
Raman Spectroscopic Method for Determining Crystallinity of Polyethylene
G.R. Strobl, W. Hagedorn. J. Polym. Sci. Part B - Polymer Physics 16, 1181-1193 (1978)
Molecular-Motion, Thermal-Expansion, and the Phase-Transitions in Paraffins: A Model for Polymers
G.R. Strobl. J. Polym. Sci. Part C - Polymer Symposium 59, 121-142 (1977)
Die molekularen Grundlagen der anisotropen thermischen Ausdehnung von Paraffinen und Polyäthylen. Eine ramanspektroskopische Untersuchung am Beispiel des N-Tritriacontans
G.R. Strobl. Coll. Polym. Sci. 254, 170-189 (1976)
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