1)A linear polystyrene has a number-average molecular weight of 400000 g/mol; co

Question

1)A linear polystyrene has a number-average molecular weight of 400000 g/mol; compute average values of L and r for this material? What is the degree of polymerization of this polymer if the number-average molecular weight is 400000 g/mol?

What is the total number of chain bonds in the molecule?

What is the total chain length L in nm?

Calculate the average chain end-to-end distance, r, in nm?

2)If the degree of polymerization of this polymer is 24000, what is its number-average molecular weight in g/mol?

3)For a linear polytetrafluoroethylene determine:

(a) the number-average molecular weight for L= 3000 nm;

(b) the number-average molecular weight for r = 17 nm.

4)An alternating copolymer is known to have a number-average molecular weight of 146000 g/mol and a degree of polymerization of 2210. If one of the repeat units is ethylene, which of styrene, propylene, tetrafluoroethylene, and vinyl chloride is the other repeat unit?

Explanation / Answer

For polyethylene, from Table 14.3, each repeat unit has two carbons and four hydrogens. Thus,

m = 2(Ac) + 4(AH)
= (2)(12.01 g/mol) + (4)(1.008 g/mol) = 28.05 g/mol
and

DP = Mn/m = (400,000 g/mol)/(28.05 g/mol) = 14260.25

which is the number of repeat units along an average chain. Since there are two carbon atoms per repeat unit, there are two C

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