Molecular weight distribution of poly(vinyl chloride)

Under the assumption that poly (vinyl chloride) (PVC) contains a negligible amount of long branches, simple kinetic considerations lead to the result that the molecular weight distribution (MWD) function resulting from a heterogeneous polymerization will be in accordance with the functional expression for the most probable distribution (mpd). A comparison between the experimental MWD curves determined by gel permeation chromatography (GPC) and the mpd supports this hypothesis and it is shown that the form of the MWD of PVC is very close to or identical with the mpd. Furthermore, it is found that PVC samples prepared by heterogeneous polymerization in the temperature interval 25–55°C have approximately identical distributions when normalized molecular weights are used. The degree of long chain branching is estimated to be equal to or less than 2 × 10−4 long branches per repetition unit.