Classical Theory of Two-dimensional Polycondensations

Flory s fundamental concept of step-growth polymerizations is based on two premisses. First. The reactivities of functional involved in the polymerization process are independent on the size of the molecules. Second, end-to-end 

The next point discussed by Flory was the relationship between DP (Flory frequently used x as symbol) and conversion. He formulated Eq. (4.2), later called Carother s equation, but he also formulated Eq. (4.3). As will be shown below, Eqs. (4.2) and (4.3) do not give the same result under aU circumstances. Anyway Eq. (4.2) demonstrates that syntheses of high molar mass polymers via polycondensation requires extremely high conversions ( 98 %) in contrast to chain-growth polymerizations. On the basis of Eq. (4.2), Mn was defined according to Eq. (4.4). 

At this point it should be emphasized that DP or x count the repeat units in the case of a — b monomers, but the sum of units resulting from 02 and A2 monomers and not the repeat units. 

Flory then considered the influence of a monofunctional additive (chain terminator) on the DP (Eq. 4.5). In the case of 2 + hi polycondensations stoichiometric imbalance has the same consequence for DP as addition of a 

DP = (moles bifunctional units excl. of stabilizers)/(moles stabilizer units) 

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