Thermodynamic properties of carbosilane dendrimers of the third to the sixth generations with terminal butyl groups in the range from T→0 to 600K

Смирнова, Н. Н.; Степанова, О. В.; Быкова, Т. А.; Маркин, А. В.; Muzafarov, А. М.; Татаринова, Е. А.; Myakushev, V. D.

doi:10.1016/j.tca.2005.11.009

Cited by 42 publications

(33 citation statements)

References 19 publications

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“…This scenario can account for the two glasslike transitions as predicted from simulations in the larger size model 28 and as verified from recent experiments. 26 Approximate values for the glass transition temperatures ͑T g ͒ of the examined models as detected in R2 are K and T g L ͑G5͒Ӎ450 K, where T g H and T g L refer to the "high" and the "low" temperature T g 's of the largest generation system.…”

Section: Non-gaussianity and Local Relaxationmentioning

confidence: 99%

“…6,16,24 In this work we aim at a closer view on those mechanisms governing local polymer motion under a dense connectivity pattern and a well defined mobility contrast, by examining polymeric models bearing the dendritic topology. Dendrimers are glass-forming polymeric materials [25][26][27][28] with a quantitatively described level of dynamic heterogeneity well localized within their structure. [27][28][29][30][31] These attributes may essentially "filter out" certain dynamic features met either in liquids or linear polymers allowing a better assessment of the relative importance of each factor.…”

Section: Introductionmentioning

confidence: 99%

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Local polymer dynamics under strong connectivity constraints: The dendrimer case

Karatasos

Lyulin

2006

The Journal of Chemical Physics

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The characteristics of local motion are explored by molecular dynamics simulations in a series of AB 2 -type dendrimer melts. Systems of generations 3-5 were simulated in a wide temperature range, allowing the assessment of effects associated with molecular size, proximity to the detected glasslike transitions, and the strong connectivity constraints imposed by the dendritic topology. Investigation of the mechanisms involved in local motion at short temporal and spatial scales revealed the connection between the non-Gaussian nature of monomer displacements to ␣-relaxation and the caging/decaging process under different degrees of confinement. In the latter mechanism, two characteristic localization lengths were identified: at the low temperature limit spatial localization was realized within approximately 10% of the nearest neighbor distance while at temperatures higher than the glass transition, the existence of an analogous length scale is ascribed to the geometric constraints due to the dense connectivity pattern. As the results from this study are discussed in comparison to the behavior observed in linear polymers and supercooled liquids, new insight is provided on the universal/specific mechanisms involved in local dynamics of different glass-forming systems.

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Section: Non-gaussianity and Local Relaxationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Local polymer dynamics under strong connectivity constraints: The dendrimer case

Karatasos

Lyulin

2006

The Journal of Chemical Physics

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“…1- 11 Since the first reports on the synthesis of carbosilane dendrimers have been pub lished, 6,7 they were used, along with other compounds with dendrite organization of the molecular structure, as objects for the determination of the thermodynamic char acteristics. [12][13][14][15][16][17][18][19] In particular, methods of precision calo rimetry were used to study the low temperature depen dence of the heat capacity in a wide temperature range, and the experimental values were used in calculating the thermodynamic functions in the temperature range from T → 0 to 340-600 K.…”

mentioning

confidence: 99%

“…We have earlier 19 obtained the standard thermody namic functions of the carbosilane dendrimers of the third-sixth generations with the terminal butyl groups in the range from T → 0 to 340-600 K and determined and analyzed changes in these functions depending on the composition and structure of compounds. The systematic studies of the temperature dependence of the heat capac ity of the dendrimers revealed the second relaxation tran sition, which is an important principal result.…”

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confidence: 99%

Thermodynamic properties of carbosilane dendrimers of the seventh and ninth generations with terminal butyl groups in the temperature range from T → 0 to 600 K

et al. 2007

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Temperature dependences of the heat capacity of carbosilane dendrimers with butyl termi nal groups of the seventh and ninth generations were determined in the temperature range from 6 to 600 K by precision adiabatic vacuum calorimetry and differential scanning (dynamic) calorimetry. The physical transitions were revealed and their thermodynamic characteristics were analyzed. The experimental data obtained were used to calculate the standard thermo dynamic functions C p (T ), H°(T ) -H°(0), S°(T ), and G°(T ) -H°(0) for the temperature range from T → 0 to 600 K. The thermodynamic function-molar weight isotherms for the dendrimers of the third-ninth generations with terminal butyl groups in the glassy and highly elastic state are linear.Investigation of the synthesis and physicochemical properties of dendrimers, being monodispersed, nano sized, regularly branched macromolecular particles, is a promising direction of the modern chemistry of high molecular weight compounds. 1-11 Since the first reports on the synthesis of carbosilane dendrimers have been pub lished, 6,7 they were used, along with other compounds with dendrite organization of the molecular structure, as objects for the determination of the thermodynamic char acteristics. 12-19 In particular, methods of precision calo rimetry were used to study the low temperature depen dence of the heat capacity in a wide temperature range, and the experimental values were used in calculating the thermodynamic functions in the temperature range from T → 0 to 340-600 K.We have earlier 19 obtained the standard thermody namic functions of the carbosilane dendrimers of the third-sixth generations with the terminal butyl groups in the range from T → 0 to 340-600 K and determined and analyzed changes in these functions depending on the composition and structure of compounds. The systematic studies of the temperature dependence of the heat capac ity of the dendrimers revealed the second relaxation tran sition, which is an important principal result. The appear ance of the transition is consistent with a change in the physical state of the dendrimers. It was of interest to elu cidate whether this transition is characteristic of dendrimer samples of higher generations from the same homological series. The presence of the transition would mean that we deal with a general phenomenon for dendrimers of high generations.The purpose of this work is the calorimetric study of the temperature dependence of the heat capacity C p° = f(T ) of the carbosilane dendrimers of the seventh and ninth generations in the temperature range from 6 to 550-600 K and elucidation and physicochemical inter pretation of possible physical transitions on heating and cooling. We also intended to calculate the standard ther modynamic functions C p (T ), H°(T ) -H°(0), S°(T ), and G°(T ) -H°(0) from the experimental data for the range from T → 0 to 550-600 K and to approximate the calcu lated thermodynamic functions to the corresponding iso therms thermodynamic function-molar weight, which have been determined...

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“…Smirnova in the Institute of Chemistry of University of N. Novgorod). 33,34 It is important that the appearance of the second transition coincides with the change of the physical state of a dendrimer samples. If till the fifth generation they are viscous transparent liquids, starting from the sixth one they behave as wax-like substances.…”

Section: Carbosilane Dendrimersmentioning

confidence: 99%

From the discovery of sodiumoxyorganoalkoxysilanes to the organosilicon dendrimers and back

Muzafarov

Rebrov

2008

J. Polym. Sci. A Polym. Chem.

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Upon being discovered 20 years ago, sodiumoxyorganoalkoxysilanes became the key to the world of organoelement dendrimers. Even considering the great variety of objects that had appeared in this area during the last 20 years, the organosilicon dendrimers are still one of the most actual objects in this class. Above all, this is fair concerning the carbosilane systems. The high reactivity of the functional groups, the well controlled chemistry of their transformations, and the inertness of the molecular skeleton are the reason for making these systems highly actual in two main regards: as model objects for the deep research of the dendrimers' properties and as polyfunctional matrixes for numerous derivatives. In this review, we were mainly focusing on the importance of the former part. In the conclusion, we showed the motivation for further development of this area both in regard of synthesis of new carbosilane systems and further development of siloxane dendrimers.

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Thermodynamic properties of carbosilane dendrimers of the third to the sixth generations with terminal butyl groups in the range from T→0 to 600K

Cited by 42 publications

References 19 publications

Local polymer dynamics under strong connectivity constraints: The dendrimer case

Local polymer dynamics under strong connectivity constraints: The dendrimer case

Thermodynamic properties of carbosilane dendrimers of the seventh and ninth generations with terminal butyl groups in the temperature range from T → 0 to 600 K

From the discovery of sodiumoxyorganoalkoxysilanes to the organosilicon dendrimers and back

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