Determination of polymer solubility parameter

1. Bangabandhu Sheikh Mujibur
Rahman Science & Technology
University
Md. Habibur Rahman Md. Muttakin
ID:20121107042 Lecturer
Dept. of ACCE Dept. of ACCE
BSMRSTU BSMRSTU

2. Determination of polymer
solubility parameter
Polymer:
Polymers are macromolecules built up by the
linking together of large numbers of much smaller
molecules.
Polymerization:
The process of linking the repeating units
(monomers) is termed as polymerization
Polymer Solution:
Polymer solutions are solutions containing
dissolved polymers. These may be liquid solutions (e.g. in
aqueous solution), or solid solutions (e.g. a substance which
has been plasticized.

3. Determining 1 (Solubility Parameter of Solvent)
E1
V1
= cohesive energy density (CED)
• “Energy required to remove a molecule from its nearest neighbor’. Similar to heat of
vaporization per volume for a volatile compound (e.g. solvent), which means the amount
of Energy required to transform a given quantity of a substance into a gas.
For a solvent, δ1 can be calculated directly from the enthalpy of vaporization (Hvap):
E = Hvap - RTR: gas constant (8.31 J/mol K)
T: temperature (K) (K = 273 + C)
V: molar volume: MW/density
δ1 =
Hvap - RT
V
1/2
Thus,
units: MPa1/2 or (J/cm3)1/2 [note: 1 MPa1/2 = 1 J/cm3 = 0.49 (cal/cm3 )1/2 ]

4. There is no direct feasible measurement for since polymers degrade before they
vaporize. There are a few commonly used methods to estimate and hence 2 for
polymers:
a) Measurement of the polymer solubility in a range of solvents; or better, measurement of the
degree of swelling of a lightly cross-linked specimen of polymer in different solvents, otherwise
it will change the chemical composition of the sample, leading to an erroneous result. at
the middle of the solubility range, or at maximum swelling, with the unmodified polymer is
taken as the value of the polymer.
.
The mid point is
taken as
Determining 2 (Solubility Parameter of a Polymer)

5. b) is taken as the value of for the solvent which gives the maximum dilute solution
viscosity, i.e. by comparing for solutions of the same concentration of polymer in several
different solvents. The best solvent gives the highest viscosity since the polymer chain is most
expanded.
c) is calculated by the method of group contributions (G, molar attraction constants) by
Small's formula, δ2= ρΣG/M .
This is an arbitrary method for estimating δ2 value of a compound by considering the
contribution of each atom or group in the compound or the repeating unit in a polymer.
Through considering the structure, polarity, attractive and repulsive forces, each atom or group
of atoms is assigned a value known as the molar-attraction constant G. The solubility parameter
is then calculated from Small’s formula. As this method is based on different physical principle
from that of using heat of vaporization , the magnitude of δ2 is here expected to be different,
where ρ is the density and M the molar wt. of the repeating unit.
The G terms in the summation are values for each different chemical group comprising the
repeat unit of a polymer (or a solvent). There are several different tables of G values in the
literature. The various tables are internally consistent, but not there is not necessarily in
agreement between them, and Gs cannot be transferred from one to the other. Note that
hydrogen bonding groups such as amide, amine, hydroxyl and carboxyl present problems if such
interactions can occur between the solvent and polymer.

6. THANKS TO ALL