epsilon - Caprolactone is polymerized using aluminum isopropoxide as the initiat
ID: 526125 • Letter: E
Question
epsilon - Caprolactone is polymerized using aluminum isopropoxide as the initiator in THF at 25 degree C [A. Duda and S. Penczek, Macromolecules, 1995, 28, 5981]. The initial monomer concentration is 1.47 molL^-1; the initial aluminum isopropoxide concentration is 1.63 times 10^-4 molL^-1. The reaction mixture is subjected to hydrolysis at the point where 100% conversion has been reached. The number average degree of polymerization of the hydrolyzed polymer is 2.99 times 10^3. Compare this value with theoretical degree of polymerization and determine the degree of functionality for the initiator.Explanation / Answer
Polycaprolactone is (C6H10O2)n
Degree of polymerisation is calculated by dividing the molecular weight of the polymer with the molecular weight of the monomer
Monomer is caprolactone with molecular weight 114
Also, average molecular weight of polycaprolactone is 65,000
Therefore, degree of polymerisation, n = 65,000/114
= 571
The nonuniformity in the distribution, U = Mw/Mn - 1
For, polycaprolactone Mw = 65000 and Mn = 42000
Therefore, U = 65000/42000 -1
= 0.5476
Relationship between the non-uniformity and degree of functionality
U = 1/f
f = 1/U
= 1/0.5476
= 1.826
Degree of functionality of initiator = 1.826
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