Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 11, pp. 2071−2074.
Pleiades Publishing, Ltd., 2009.
Original Russian Text
I.S. Saddikov, 2009, published in Zhurnal Prikladnoi Khimii, 2009, Vol. 82, No. 11, pp. 1922−1925.
Phase Transitions in Polystyrene Solutions Induced
by a Longitudinal Hydrodynamic Field
I. S. Saddikov
Tadjik Agrarian University, Dushanbe, Tajikistan
Received October 1, 2008
Abstract—The flow of solutions of polystyrene with various molecular weights in a longitudinal hydrodynamic
field was studied. The stepwise variation of such state parameters as volume and entropy of flexible chain
macromolecules was observed on the skein-unrolled chain transition. To describe this transition, a modified Van
der Waals’ equation taking into consideration the deviation of the system from ideality was proposed.
Equilibrium state variations passing from one phase
into another under the action of a mechanical ﬁ eld are
observed in heterogeneous systems such as polymeric
solutions. The phases are in equilibrium, and the action
of a longitudinal hydrodynamic ﬁ eld gives rise to the
transition of a macromolecule from the skein state to the
straightened-chain state. It is known that the ﬁ rst-order
phase transitions are accompanied by a stepwise volume
change and by a heat absorption or evolution.
The volume occupied by a macromolecule in the skein
state in an ideal solvent is deﬁ ned by the formula
were A is a segment length, N, a number of segments,
, a skein radius.
The volume of a completely unrolled chain consisting
of N segments with a volume A
It follows from the analysis of molar volumes of
macromolecules in view of formulas (1) and (2) the molar
volume of a skein is not equal to the molar volume of
a straightened chain with the same number N of segments.
It was shown in  that the stepwise variation of a macro-
molecule volume and also a stepwise variation of a molar
is connected with the absorption of a heat
λ of the transition, which is described by the relation λ =
). It is afﬁ rmed in  that the ﬁ rst-order phase
transition requires the condition S
to be fulﬁ lled
when λ ≠ 0.
In view of formulas (1) and (2) the Clapeyron-Clausius
equation for transition of a macromolecule from a skein
state to a straightened-chain state can be written in the
form of 
were k = 4.2.
Equation (3) characterizes the transition of a polymeric
compound from one state to another by a principle of the
ﬁ rst-order phase transition. For example, at N = 5 × 10
the relative volume of segments of the macromolecule,
which are in the skein state, is 300-fold greater than the
volume of the unrolled chain.
In turn, the dynamic characteristics of a macromolecule
deﬁ ning its behavior both during an orientation and a de-
formation can be completely described by the relaxation
[3, 4]. Under the action of hydrodynamic ﬁ elds
the relaxation time is deﬁ ned by the formula