NMR analysis of chlorinated poly(vinyl chloride)

The chlorination of poly(vinyl chloride) takes place preferentially at the methylenic carbon, leading to 1,2‐dichloroethylenic units, and to a lower extent at the methynic, leading to 1,1‐dichloroethylenic units. The ratio between 1,2‐ and 1,1‐dichloroethylenic units tends to decrease with increasing degree of chlorination, and it seems to depend also on the chlorination conditions. The number‐average sequence length of 1,2‐dichloroethylenic units does not differ significantly from 1 during a great part of the process, substantially in agreement with a random distribution of these units along the chain. The 1,1‐dichloroethylenic units can be found either between two unchlorinated units or at one end of a sequence of chlorinated units. Since among the unchlorinated units more racemic units are present than expected for a completely random chlorination, it can be suggested either that chlorination is affected by stereoregularity or that it does not take place in the crystalline regions of the polymer.