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Kohlbrecher J, Breßler I. Updates in SASfit for fitting analytical expressions and numerical models to small-angle scattering patterns. J Appl Crystallogr 2022; 55:1677-1688. [PMID: 36570652 PMCID: PMC9721323 DOI: 10.1107/s1600576722009037] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Accepted: 09/09/2022] [Indexed: 11/22/2022] Open
Abstract
Small-angle scattering is an increasingly common method for characterizing particle ensembles in a wide variety of sample types and for diverse areas of application. SASfit has been one of the most comprehensive and flexible curve-fitting programs for decades, with many specialized tools for various fields. Here, a selection of enhancements and additions to the SASfit program are presented that may be of great benefit to interested and advanced users alike: (a) further development of the technical basis of the program, such as new numerical algorithms currently in use, a continuous integration practice for automated building and packaging of the software, and upgrades on the plug-in system for easier adoption by third-party developers; (b) a selection of new form factors for anisotropic scattering patterns and updates to existing form factors to account for multiple scattering effects; (c) a new type of a very flexible distribution called metalog [Keelin (2016). Decis. Anal. 13, 243-277], and regularization techniques such as the expectation-maximization method [Dempster et al. (1977). J. R. Stat. Soc. Ser. B (Methodological), 39, 1-22; Richardson (1972) J. Opt. Soc. Am. 62, 55; Lucy (1974). Astron. J. 79, 745; Lucy (1994). Astron. Astrophys. 289, 983-994], which is compared with fits of analytical size distributions via the non-linear least-squares method; and (d) new structure factors, especially for ordered nano- and meso-scaled material systems, as well as the Ornstein-Zernike solver for numerical determination of particle interactions and the resulting structure factor when no analytical solution is available, with the aim of incorporating its effects into the small-angle scattering intensity model used for fitting with SASfit.
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Affiliation(s)
- Joachim Kohlbrecher
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland,Correspondence e-mail: ,
| | - Ingo Breßler
- BAM Federal Institute for Materials Research and Testing, 12205 Berlin, Germany,Correspondence e-mail: ,
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Kang JJ, Sachse C, Ko CH, Schroer MA, Vela SD, Molodenskiy D, Kohlbrecher J, Bushuev NV, Gumerov RA, Potemkin II, Jordan R, Papadakis CM. Rigid-to-Flexible Transition in a Molecular Brush in a Good Solvent at a Semidilute Concentration. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:5226-5236. [PMID: 35166545 DOI: 10.1021/acs.langmuir.1c02589] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The structures of a molecular brush in a good solvent are investigated using synchrotron small-angle X-ray scattering in a wide range of concentrations. The brush under study, PiPOx239-g-PnPrOx14, features a relatively long poly(2-isopropenyl-2-oxazoline) (PiPOx) backbone and short poly(2-n-propyl-2-oxazoline) (PnPrOx) side chains. As a solvent, ethanol is used. By model fitting, the overall size and the persistence length as well as the interaction length and interaction strength are determined. At this, the interplay between form and structure factor is taken into account. The conformation of the molecular brush is traced upon increasing the solution concentration, and a rigid-to-flexible transition is found near the overlap concentration. Finally, the results of computer simulations of the molecular brush solutions confirm the experimental results.
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Affiliation(s)
- Jia-Jhen Kang
- Fachgebiet Physik weicher Materie, Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
| | - Clemens Sachse
- Professur für Makromolekulare Chemie, Fakultät Chemie und Lebensmittelchemie, Technische Universität Dresden, Mommsenstraße 4, 01069 Dresden, Germany
| | - Chia-Hsin Ko
- Fachgebiet Physik weicher Materie, Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
| | - Martin A Schroer
- European Molecular Biology Laboratory, Hamburg Outstation, c/o Deutsches Elektronen-Synchrotron, Notkestr. 85, 22607 Hamburg, Germany
| | - Stefano Da Vela
- European Molecular Biology Laboratory, Hamburg Outstation, c/o Deutsches Elektronen-Synchrotron, Notkestr. 85, 22607 Hamburg, Germany
| | - Dmitry Molodenskiy
- European Molecular Biology Laboratory, Hamburg Outstation, c/o Deutsches Elektronen-Synchrotron, Notkestr. 85, 22607 Hamburg, Germany
| | - Joachim Kohlbrecher
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, Forschungsstr. 111, 5232 Villigen PSI, Switzerland
| | - Nikita V Bushuev
- Physics Department, Lomonosov Moscow State University, Moscow 119991, Russian Federation
| | - Rustam A Gumerov
- Physics Department, Lomonosov Moscow State University, Moscow 119991, Russian Federation
| | - Igor I Potemkin
- Physics Department, Lomonosov Moscow State University, Moscow 119991, Russian Federation
- National Research South Ural State University, Chelyabinsk 454080, Russian Federation
| | - Rainer Jordan
- Professur für Makromolekulare Chemie, Fakultät Chemie und Lebensmittelchemie, Technische Universität Dresden, Mommsenstraße 4, 01069 Dresden, Germany
| | - Christine M Papadakis
- Fachgebiet Physik weicher Materie, Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
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