Question

A sample of polyethylene C2H4 has a coiled length of 3.27 mm. Calculate the degree of polymerization?

Answer 1

Given, Coiled length of polyethylen sample = 3.27 mm, i.e. 3.27*10^-3 m.

The structure of polyethylene can be drwan as

Here, we have to find the value of n, i.e. degree of polymerization.

We know that, all carbon atoms in the polyethylene chain shown above are in SP³ hybridizaiton and C‒C bond length is 1.54 Å and the tetrahedral bond angle is 109.5 Å.

The distance benween two adjacent carbon atoms in the polyethylene shown above is

1.54*Sin(109.5/2)^o = 1.54*Sin(54.75)^o = 1.54*0.82 = 1.26 Å

Since each monomer molecule (C₂H₄) has two carbon atoms,

1.26*10^-10*2*n = 3.27*10^-3 (Since 1 Å = 10^-10 m)

Therefore, the degree of polymerization of polyethylene, i.e. n = 1.3*10⁷