Question

polyamide was prepared by bulk polymerization of hexamethylene diamine (9.22 g) with adipic acid (11.68 g) at 280 °C. Analysis of the whole reaction product showed that it contained 2.6 × 10−3 mol of carboxylic acid groups. Evaluate the number-average molar mass Mn of the polyamide, and also estimate its weight-average molar mass Mw by assuming that it has the most probable distribution of molar mass. t The answers are that Mn= 8.58 kg/mol and Mw = 17.07 kg/mol and Xn= 75.9

Answer 1

Solution:

Explanation:

Number-average molar mass Mn:

The number average molar mass is nothing but the arithmetic mean of the of the molecular masses of the individual macromolecules, and it is also represented as Number Average Molecular Weight.

Where N_i = No. of moles of each polymer groups

and M_i = molar mass or wt. of that species.

Let, A represents hexamethylene diamine and B represents adipic acid.

Molecular wt. of A = 116.21 g/mol and B = 146.14 g/mol

Molecular Weight of the carboxylic acid group: 224.219 g/mol

Then,

mole of A = 9.22/116.21 = 0.07934 mol

Mol of B =11.68/146.14 = 0.07992 mol

mol of C = 0.0026 mol

from the equation 1st,

b)

Weight average molar mass:

The Weight average molar mass is nothing but the arithmetic mean of the of the molar masses of the polymer, and it is also known as Mass Average Molecular Weight.