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Markelov DA, Dolgushev M, Gotlib YY, Blumen A. NMR relaxation of the orientation of single segments in semiflexible dendrimers. J Chem Phys 2015; 140:244904. [PMID: 24985675 DOI: 10.1063/1.4884024] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We study the orientational properties of labeled segments in semiflexible dendrimers making use of the viscoelastic approach of Dolgushev and Blumen [J. Chem. Phys. 131, 044905 (2009)]. We focus on the segmental orientational autocorrelation functions (ACFs), which are fundamental for the frequency-dependent spin-lattice relaxation times T1(ω). We show that semiflexibility leads to an increase of the contribution of large-scale motions to the ACF. This fact influences the position of the maxima of the [1/T1]-functions. Thus, going from outer to inner segments, the maxima shift to lower frequencies. Remarkably, this feature is not obtained in the classical bead-spring model of flexible dendrimers, although many experiments on dendrimers manifest such a behavior.
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Affiliation(s)
- Denis A Markelov
- Faculty of Physics, St. Petersburg State University, Ulyanovskaya Str. 1, Petrodvorets, St. Petersburg, 198504 Russia
| | - Maxim Dolgushev
- Theoretical Polymer Physics, University of Freiburg, Hermann-Herder-Str. 3, D-79104 Freiburg, Germany
| | - Yuli Ya Gotlib
- Faculty of Physics, St. Petersburg State University, Ulyanovskaya Str. 1, Petrodvorets, St. Petersburg, 198504 Russia
| | - Alexander Blumen
- Theoretical Polymer Physics, University of Freiburg, Hermann-Herder-Str. 3, D-79104 Freiburg, Germany
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Markelov DA, Polotsky AA, Birshtein TM. Formation of a "Hollow" Interior in the Fourth-Generation Dendrimer with Attached Oligomeric Terminal Segments. J Phys Chem B 2014; 118:14961-71. [PMID: 25438194 DOI: 10.1021/jp509151w] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
By using the Scheutjens-Fleer self-consistent field approach, the structure of the fourth-generation dendrimer with attached terminal chemically different oligomeric segments is studied theoretically. It is demonstrated that an incompatibility of terminal segments with inner dendrimer units leads to formation of a "hollow" core with reduced polymer density in the dendrimer center. This effect is enhanced with a deterioration in the solvent quality for terminal segments. This observation is in accordance with experimental results and molecular dynamics simulation data for an analogous system. It is established that the main factor determining the hollow core formation is the segregation between inner and terminal units because the main driving force for the effect is the localization of the terminal segments at the dendrimer periphery. The influence of structural parameters of dendrimer such as the number of generations and length of the terminal chain on this effect is also studied.
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Affiliation(s)
- Denis A Markelov
- Faculty of Physics, St. Petersburg State University , Ulyanovskaya Street 1, Petrodvorets, St. Petersburg 198504, Russia.,St. Petersburg National Research University of Information Technologies, Mechanics and Optics (ITMO University) , Kronverkskiy Prospect 49, St. Petersburg 197101, Russia
| | - Alexey A Polotsky
- St. Petersburg National Research University of Information Technologies, Mechanics and Optics (ITMO University) , Kronverkskiy Prospect 49, St. Petersburg 197101, Russia.,Institute of Macromolecular Compounds, Russian Academy of Sciences , Bolshoi Prospect 31, V.O., St. Petersburg 199004, Russia
| | - Tatiana M Birshtein
- Faculty of Physics, St. Petersburg State University , Ulyanovskaya Street 1, Petrodvorets, St. Petersburg 198504, Russia.,Institute of Macromolecular Compounds, Russian Academy of Sciences , Bolshoi Prospect 31, V.O., St. Petersburg 199004, Russia
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Affiliation(s)
- Jingjing Hu
- CAS Key Laboratory of Soft Matter
Chemistry, Department of Chemistry, University of Science and Technology of China, Hefei, Anhui, 230026, People’s
Republic of China
| | - Tongwen Xu
- CAS Key Laboratory of Soft Matter
Chemistry, Department of Chemistry, University of Science and Technology of China, Hefei, Anhui, 230026, People’s
Republic of China
| | - Yiyun Cheng
- Shanghai Key Laboratory of Regulatory
Biology, School of Life Sciences, East China Normal University, Shanghai, 200241, People’s Republic of China
- Shanghai
Key Laboratory of Magnetic
Resonance, Department of Physics, East China Normal University, Shanghai, 200062, P.R.China
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Markelov DA, Matveev VV, Ingman P, Nikolaeva MN, Lähderanta E, Shevelev VA, Boiko NI. NMR Studies of Carbosilane Dendrimer with Terminal Mesogenic Groups. J Phys Chem B 2010; 114:4159-65. [DOI: 10.1021/jp909658v] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Denis A. Markelov
- Laboratory of Physics, Lappeenranta University of Technology, Box 20, 53851 Lappeenranta, Finland, Faculty of Physics, St. Petersburg State University, Ulyanovskaya Str. 1, Petrodvorets, St. Petersburg, 198504 Russia, Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoi Prospect 31, V.O., St. Petersburg, 199004 Russia, Instrument Centre, Department of Chemistry, University of Turku, Vatselankatu 2, FI-20014, Turku, Finland, and Faculty of Chemistry, Moscow State University,
| | - Vladimir V. Matveev
- Laboratory of Physics, Lappeenranta University of Technology, Box 20, 53851 Lappeenranta, Finland, Faculty of Physics, St. Petersburg State University, Ulyanovskaya Str. 1, Petrodvorets, St. Petersburg, 198504 Russia, Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoi Prospect 31, V.O., St. Petersburg, 199004 Russia, Instrument Centre, Department of Chemistry, University of Turku, Vatselankatu 2, FI-20014, Turku, Finland, and Faculty of Chemistry, Moscow State University,
| | - Petri Ingman
- Laboratory of Physics, Lappeenranta University of Technology, Box 20, 53851 Lappeenranta, Finland, Faculty of Physics, St. Petersburg State University, Ulyanovskaya Str. 1, Petrodvorets, St. Petersburg, 198504 Russia, Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoi Prospect 31, V.O., St. Petersburg, 199004 Russia, Instrument Centre, Department of Chemistry, University of Turku, Vatselankatu 2, FI-20014, Turku, Finland, and Faculty of Chemistry, Moscow State University,
| | - Marianna N. Nikolaeva
- Laboratory of Physics, Lappeenranta University of Technology, Box 20, 53851 Lappeenranta, Finland, Faculty of Physics, St. Petersburg State University, Ulyanovskaya Str. 1, Petrodvorets, St. Petersburg, 198504 Russia, Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoi Prospect 31, V.O., St. Petersburg, 199004 Russia, Instrument Centre, Department of Chemistry, University of Turku, Vatselankatu 2, FI-20014, Turku, Finland, and Faculty of Chemistry, Moscow State University,
| | - Erkki Lähderanta
- Laboratory of Physics, Lappeenranta University of Technology, Box 20, 53851 Lappeenranta, Finland, Faculty of Physics, St. Petersburg State University, Ulyanovskaya Str. 1, Petrodvorets, St. Petersburg, 198504 Russia, Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoi Prospect 31, V.O., St. Petersburg, 199004 Russia, Instrument Centre, Department of Chemistry, University of Turku, Vatselankatu 2, FI-20014, Turku, Finland, and Faculty of Chemistry, Moscow State University,
| | - Vladimir A. Shevelev
- Laboratory of Physics, Lappeenranta University of Technology, Box 20, 53851 Lappeenranta, Finland, Faculty of Physics, St. Petersburg State University, Ulyanovskaya Str. 1, Petrodvorets, St. Petersburg, 198504 Russia, Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoi Prospect 31, V.O., St. Petersburg, 199004 Russia, Instrument Centre, Department of Chemistry, University of Turku, Vatselankatu 2, FI-20014, Turku, Finland, and Faculty of Chemistry, Moscow State University,
| | - Natalia I. Boiko
- Laboratory of Physics, Lappeenranta University of Technology, Box 20, 53851 Lappeenranta, Finland, Faculty of Physics, St. Petersburg State University, Ulyanovskaya Str. 1, Petrodvorets, St. Petersburg, 198504 Russia, Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoi Prospect 31, V.O., St. Petersburg, 199004 Russia, Instrument Centre, Department of Chemistry, University of Turku, Vatselankatu 2, FI-20014, Turku, Finland, and Faculty of Chemistry, Moscow State University,
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Filip D, Cruz C, Sebastião PJ, Cardoso M, Ribeiro AC, Vilfan M, Meyer T, Kouwer PHJ, Mehl GH. Phase structure and molecular dynamics of liquid-crystalline side-on organosiloxane tetrapodes. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 81:011702. [PMID: 20365386 DOI: 10.1103/physreve.81.011702] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2009] [Indexed: 05/29/2023]
Abstract
X-ray diffraction and proton NMR relaxation measurements were carried out on two liquid-crystalline organosiloxane tetrapodes with side-on mesogenic groups, exhibiting nematic and smectic- C phases, and on a monomeric analog. Packing models for the mesophases exhibited by these systems are proposed on the basis of x-ray diffraction data. As a consequence of microsegregation, the aromatic cores are packed in between two sublayers formed by a mixture of interdigitated aliphatic and siloxane chains. The mixed sublayers are characteristic for the tetrapodes with side-on mesogenic groups presented in this work and have not been observed in tetrapodes with terminally attached mesogens. The tilt angle in the smectic- C phase is found very large, i.e., approximately 61 degrees -62 degrees . Notably, smectic- C clusters are present also in the whole temperature range of the nematic phase. NMR relaxometry yields T(1)-1 dispersions clearly different from those of conventional calamitics. The influence of molecular tendency to form interdigitated structures is evidenced by frequency-dependent relaxation rate in the isotropic phase-indicating the presence of ordered clusters far above the phase transition-and by the diminished role of molecular self-diffusion in ordered phases. Nematiclike director fluctuations are the dominating relaxation mechanism whereas the translational displacements are strongly hindered by the interdigitation of dendrimer arms.
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Affiliation(s)
- D Filip
- Centro de Física da Matéria Condensada, Universidade de Lisboa, Lisboa, Portugal
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