Nanoscale physics

Structure of nanoclusters and density of solutions of rigid-chain polymers 
Bulavin L.A.1, Zabashta Yu.F.1, Lazarenko M.M.1, 
Alekseev O.M.1, Vergun L.Yu.1

1 Taras Shevchenko National University of Kyiv.
64/13, Volodymyrska Street, City of Kyiv, Ukraine, 01601
E-mail: LienaVergun@univ.net.ua

As is known, a feature of the polymer solution is the presence of nanoclusters. The nanoclasters are  nanosized aggregates consisting of a polymer chain and related solvent molecules. The literature mainly refers to (see, for example, [1], etc.) nanoclusters formed by flexible chains. Instead, this report considers nanoclusters containing rigid chains.
A continuous model of polymer solution is proposed. According to this model the solution is considered as a set of three phases: solvent and two phases, which make up the nanocluster, namely, the core and the boundary layer.
The formulas that relate the density of the solution with the densities of these phases are derived. The temperature dependence of the density of the aqueous solution of hydroxypropylmethylcellulose (typical representative of the class of rigid chain polymers) is experimentally investigated. The experiment was performed on a Density meter: Anton Paar DMA 4500 M in the range of          293 K-353K.
Based on the obtained experimental data using the derived formulas, and data borrowed from [2], a structural model of a rigid-chain nanocluster was built. For  such model  the core has a cylindrical shape and is formed by a threefold chain, and the boundary layer is formed by water molecules. The orientation of water molecules  changes with increasing temperature.

1.	De Gennes  Pierre-Gilles. Scaling Concepts in Polymer Physics// Cornell University Press.-1979.-319p.
2.	Alekseev O.M., Zabashta Yu.F., Kovalchuk V.I., Lazarenko M.M.,  Bulavin L.A.  The structure of polymer clusters in aqueous solutions of hydroxypropyl cellulose// Ukr. j. phys.- 2019.-64,N 3.-P.238-244.