Change and Convergence of Polymer Distribution During Nonrandom Degradation

The CLD development during nonrandom degradation is investigated, assuming the rate of bond scission depends on the chain length and the position of the bond within the chain. As the degradation proceeds, the polydispersity index (PDI = -(P) over bar (w)/(P) over bar (n)) usually approaches a fixed value pertinent to the degradation mechanism, independent of the initial distribution. The exact limiting values are presented for several cases. These values may be useful to estimate the degradation mechanisms. For example, if the limiting PDI is smaller than 2, the bonds in larger chains may be easier to break than shorter ones, and if it is smaller than 4/3, the size effect is not enough and the breakage may tend to occur in the middle of the chain.