Thermodynamic properties of carbosilane dendrimers of the third and sixth generations with ethyleneoxide terminal groups

Смирнова, Н. Н.; Маркин, А. В.; Letyanina, I. A.; Sologubov, Semen S.; Novozhilova, Natalia A.; Татаринова, Е. А.; Музафаров, А. М.

doi:10.1134/s0036024414050306

Cited by 11 publications

(10 citation statements)

References 14 publications

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“…Our choice is determined, first of all, by numerous experimental data collected over the past 10 years on these systems and an unusual behavior reported for high generation dendrimers. In particular, extensive experimental studies of poly(butylcarbosilane) dendrimers by various experimental techniques (viscometry, precision adiabatic vacuum and differential scanning calorimetry, small-angle dynamic light scattering, and atomic force microscopy) have shown that increasing dendrimer generation causes a qualitative change of the melt properties. ,− Namely, while low generation dendrimers demonstrate liquid-like behavior, the high generation dendrimers acquire properties typical for solids. This transition occurs when switching from the sixth to the seventh generation in 3–3 dendrimers (the first number 3 stands for the core functionality while the second number 3 denotes the functionality of the branching points).…”

Section: Introductionmentioning

confidence: 99%

Insight into the Structure of Polybutylcarbosilane Dendrimer Melts via Extensive Molecular Dynamics Simulations

2016

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Extensive molecular dynamics simulations of polybutylcarbosilane dendrimer melts were performed in a wide temperature range from 300 to 600 K. The melt macroscopic and structural characteristics were analyzed for the third up to the eighth generation dendrimers for the systems consisting of 8 and 27 dendrimer molecules in the simulation box. For every system, averaging was performed over 8 independent simulation runs and along equilibrium time trajectories of up to 5 ns. Calculated values of the thermal expansion coefficients, heat capacity, and self-diffusion coefficients are in a good agreement with experimental observations. Analysis of the molecular mass dependence of the gyration radius and shape factor, detailed radial density distributions of dendrimer structural units, mobility of the branching points, and intermolecular interaction energy allowed to shed light on the basics of distinction in behavior of low and high generation dendrimer melts and formulate the directions of further research.

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Section: Introductionmentioning

confidence: 99%

Insight into the Structure of Polybutylcarbosilane Dendrimer Melts via Extensive Molecular Dynamics Simulations

2016

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“…The rheology of the synthesized compounds in bulk is of particular interest. It has been mentioned above that a transition from a liquid-like to a solid-like behavior was found for non-functional carbosilane dendrimers with butyl-terminated groups upon increasing dendrimer generation [ 29 , 30 , 31 , 32 , 33 , 34 ]. This transition was accompanied by a very strong jump-like rise in melt viscosity [ 34 ].…”

Section: Resultsmentioning

confidence: 99%

“…At the same time, the storage modulus of dendrimer melts became much higher than the loss modulus G’’, starting from the 6th generation. It was suggested that such a unique change in viscoelastic properties of dendrimer melts is associated with the specific regular tree-like architecture of dendrimers and it could be related to the formation of a spatial physical network by neighboring dendrimer molecules via the penetration of peripheral groups into the surface layer of neighboring macromolecules [ 29 , 30 ]. It could be assumed that a change in the nature of the peripheral layer of the dendrimer molecules would have an impact on this alleged process.…”

Section: Resultsmentioning

confidence: 99%

“…The first intriguing result was obtained several years ago when extensively studying three homologues series of polybutylcarbosilate dendrimers differing in the functionalities of the core and branching Si atoms (3-3, 4-3 and 4-4 dendrimers). Namely, a transition from a liquid-like to a solid-like behavior of carbosilane dendrimer melts was detected, which was expressed as a second transition on the temperature dependence of the heat capacity [ 29 , 30 , 31 , 32 , 33 ]. This qualitative change of the melt properties was demonstrated for all homologues series and it required some explanation.…”

Section: Introductionmentioning

confidence: 99%

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Hybrid Polycarbosilane-Siloxane Dendrimers: Synthesis and Properties

et al. 2021

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A series of carbosilane dendrimers of the 4th, 6th, and 7th generations with a terminal trimethylsilylsiloxane layer was synthesized. Theoretical models of these dendrimers were developed, and equilibrium dendrimer conformations obtained via molecular dynamics simulations were in a good agreement with experimental small-angle X-ray scattering (SAXS) data demonstrating molecule monodispersity and an almost spherical shape. It was confirmed that the glass transition temperature is independent of the dendrimer generation, but is greatly affected by the chemical nature of the dendrimer terminal groups. A sharp increase in the zero-shear viscosity of dendrimer melts was found between the 5th and the 7th dendrimer generations, which was qualitatively identical to that previously reported for polycarbosilane dendrimers with butyl terminal groups. The viscoelastic properties of high-generation dendrimers seem to follow some general trends with an increase in the generation number, which are determined by the regular branching structure of dendrimers.

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“…The phase between these two C p features was studied by different experimental methods 15 , 17 – 20 , 28 , 29 . It has been suggested that the anomalous phase is a consequence of the physical entanglements in melts of high generation dendrimers 19 , 28 .…”

Section: Introductionmentioning

confidence: 99%

Investigation of Melts of Polybutylcarbosilane Dendrimers by 1H NMR Spectroscopy

Матвеев

Markelov

Dvinskikh

et al. 2017

Sci Rep

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Melts of polybutylcarbosilane (PBC) dendrimers from third (G3) up to sixth (G6) generations are investigated by 1H NMR spectroscopy in a wide temperature range up to 493 K. At room temperature, NMR spectra of G3-G5 dendrimers exhibit resolved, solution-like spectra (“liquid” phase). In contrast, the spectrum of the G6 dendrimer is characterized by a single unresolved broad line at whole temperature range, which supports the presence of an anomalous phase state of G6 at temperatures higher than glass transition temperature. For the first time, an unexpected transition of G5 dendrimer from a molecular liquid state to an anomalous state/phase upon temperature increase has been detected using NMR data. Specifically, an additional wide background line appears in the G5 spectrum above 473 K, and this line corresponds to a G5 state characterized by restricted molecular mobility, i.e., a state similar to the “anomalous” phase of G6 melt. The fraction of the G5 dendrimers in “anomalous” phase at 493 K is approximately 40%. Analysis of the spectral shapes suggests that changes in the G5 dendrimers are reversible with temperature.

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Thermodynamic properties of carbosilane dendrimers of the third and sixth generations with ethyleneoxide terminal groups

Cited by 11 publications

References 14 publications

Insight into the Structure of Polybutylcarbosilane Dendrimer Melts via Extensive Molecular Dynamics Simulations

Insight into the Structure of Polybutylcarbosilane Dendrimer Melts via Extensive Molecular Dynamics Simulations

Hybrid Polycarbosilane-Siloxane Dendrimers: Synthesis and Properties

Investigation of Melts of Polybutylcarbosilane Dendrimers by 1H NMR Spectroscopy

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