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In JoVE (1)
- Studying Soft-matter and Biological Systems over a Wide Length-scale from Nanometer and Micrometer Sizes at the Small-angle Neutron Diffractometer KWS-2
Other Publications (3)
Articles by Gerald J. Schneider in JoVE
Studying Soft-matter and Biological Systems over a Wide Length-scale from Nanometer and Micrometer Sizes at the Small-angle Neutron Diffractometer KWS-2
Aurel Radulescu1, Noemi Kinga Szekely1, Marie-Sousai Appavou1, Vitaliy Pipich1, Thomas Kohnke1, Vladimir Ossovyi1, Simon Staringer1, Gerald J. Schneider2, Matthias Amann3, Bo Zhang-Haagen3, Georg Brandl1, Matthias Drochner4, Ralf Engels4, Romuald Hanslik5, Günter Kemmerling1
1Jülich Centre for Neutron Science Outstation at MLZ, Forschungszentrum Jülich GmbH, 2Department of Chemistry, Louisiana State University, 3Jülich Centre for Neutron Science JCNS-1 & Institute of Complex Systems ICS-1, Forschungszentrum Jülich GmbH, 4Central Institute of Engineering, Electronics and Analytics — Electronic Systems (ZEA-2), Forschungszentrum Jülich GmbH, 5Central Institute of Engineering, Electronics and Analytics — Engineering and Technology (ZEA-1), Forschungszentrum Jülich GmbH
Other articles by Gerald J. Schneider on PubMed
The Journal of Chemical Physics. Nov, 2009 | Pubmed ID: 19895040
Poly(ethylene oxide) confined in an anodic aluminum oxide solid matrix has been studied by different neutron scattering techniques in the momentum transfer (Q) range 0.2
The Review of Scientific Instruments. Jul, 2012 | Pubmed ID: 22852726
SPHERES is a third-generation neutron backscattering spectrometer, located at the 20 MW German neutron source FRM II and operated by the Jülich Centre for Neutron Science. It offers an energy resolution (fwhm) better than 0.65 μeV, a dynamic range of ± 31 μeV, and a signal-to-noise ratio of up to 1750:1.
Monitoring the Internal Structure of Poly(N-vinylcaprolactam) Microgels with Variable Cross-link Concentration
Langmuir : the ACS Journal of Surfaces and Colloids. Dec, 2014 | Pubmed ID: 25493607
The combination of a set of complementary techniques allows us to construct an unprecedented and comprehensive picture of the internal structure, temperature dependent swelling behavior, and the dependence of these properties on the cross-linker concentration of microgel particles based on N-vinylcaprolactam (VCL). The microgels were synthesized by precipitation polymerization using different amounts of cross-linking agent. Characterization was performed by small-angle neutron scattering (SANS) using two complementary neutron instruments to cover a uniquely broad Q-range with one probe. Additionally we used dynamic light scattering (DLS), atomic force microscopy (AFM), and differential scanning calorimetry (DSC). Previously obtained nuclear magnetic resonance spectroscopy (NMR) results on the same PVCL particles are utilized to round the picture off. Our study shows that both the particle radius and the cross-link density and therefore also the stiffness of the microgels rises with increasing cross-linker content. Hence, more cross-linker reduces the swelling capability distinctly. These findings are supported by SANS and AFM measurements. Independent DLS experiments also found the increase in particle size but suggest an unchanged cross-link density. The reason for the apparent contradiction is the indirect extraction of the parameters via a model in the evaluation of DLS measurements. The more direct approach in AFM by evaluating the cross section profiles of observed microgel particles gives evidence of significantly softer and more deformable particles at lower cross-linker concentrations and therefore verifies the change in cross-link density. DSC data indicate a minor but unexpected shift of the volume phase transition temperature (VPTT) to higher temperatures and exposes a more heterogeneous internal structure of the microgels with increasing cross-link density. Moreover, a change in the total energy transfer during the VPT gives evidence that the strength of hydrogen bonds is significantly affected by the cross-link density. A strong and reproducible deviation of the material density of the cross-linked microgel polymer chains toward a higher value compared to the respective linear chains has yet to be explained.