Chap._900003 - 10 0.99 100 0.999 1000 p 1 1 Xn # of...

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* Molecular Weight of Polymer (Mn) Degree of polymerization (Xn) : the total number of structural units per polymer chain (each repeating unit consists of two structure units, i.e. monomers ) Xn = N o N [M o ] [M] = N o : total numer of functional groups initial present N : number of functional group at time t = 1 1 - p Extend of reaction (p) [M o ] -[M] [M o ] = Xn [M o ] [M] = Mn = M st Xn + M eg M st is the mean of the molecular weights of two structural units. M eg is the molecular weight of the end groups M o 1 - p ~ [M] = [M o ] (1 - p) [M] : monomer concentration equivalence of functional groups 0 1 0.5 2 0.9
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Unformatted text preview: 10 0.99 100 0.999 1000 p 1 1 Xn # of molecules or # of polymer chains 100 50 p % conversion Xn At the end of the reaction, no monomer is left and all the monomers become parts of polymers. However, the polymer only achieves high molecular weight at very high conversion and the reaction usually requires quiet long time. Theoretically, at the optimal end of the reaction, all monomers become a single polymer chain with almost infinite polymer molecular weight. However, it is very difficult to reach the end point....
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