Thermodynamics of carbosilanecyclesiloxane dendrimers

Y. Samosudova1, A. Markin1, N. Smirnova1, E. Katarzhnova2, G. Ignateva2 and A. Muzafarov2

1Research Institute of Chemistry Nizhny Novgorod State University, Russia
2Enikolopov Institute of Synthetic Polymer Materials, Russian Academy of Sciences, Russia

Keywords: calorimetry
property: heat capacity, phase transition, thermodynamic functions
material: polymer

Dendrimers are highly-branched cascade polymers with regular structure which have been received by regular synthesis and related to a new class of polymer materials called "macromolecular nanoobjects". The introduction of cyclesiloxane fragments into outer shell opens up possibility of production dendritic networks with controlled relation of carbosilane and siloxane fragments at the expense of implementation of polymerization processes. In contrast to polycondensation versions of formation networks ring-opening polymerization isn’t attended by elimination of low-molecular impurities and can be realized in nonequilibrium mode.

For the first time the temperature dependences of the heat capacity of four representatives of carbosilanecyclesiloxane dendrimers have been determine in over the range from 6 to 350 K by adiabatic vacuum calorimetry and from 300 to 520 K by differential scanning calorimeter. In the above temperature ranges the physical transformations have been detected and their standard thermodynamic characteristics have been estimated and analyzed versus of their composition and structure. The results were used to calculate the thermodynamic functions: the heat capacity, enthalpy, entropy, residual entropy and Gibbs function over the range from 0 to 520 K for different physical states, the standard entropies of formation of dendrimers at Т = 298.15 К and at standard pressure have been also calculated.

The low-temperature (Т ≤ 50 K) dependence of the heat capacity was analyzed with using Debye's the heat capacity theory of solids and multifractal model, values of fractal dimension D have been determined and some conclusions about structure topology were made.

The standard thermodynamic properties of studied dendrimers and also existing in literature data for carbosilane and carbosilansiloxane dendrimers of corresponding generations have been compared.

The work was performed with the financial support of Russian Foundation of Basic Research (Project Number 11-03-00592-a)

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