| Abstract: | The properties of poly(vinyl chloride) samples prepared by a free-radical process in the presence of n-butyraldehyde have been studied from the point of view of polymer tacticity, branching, molecular weight, and relative crystallinity. The postulate of a polymer radical–aldehyde complex, invoked to explain the increased crystallinity, was tested. The polymers had a lower degree of polymerization and branching than normal, and these parameters rather than increased syndiotacticity were responsible for the high degree of crystallinity. Both molecular weight and branching affect the crystallinity, since polymer samples prepared in the presence of various transfer agents with similar molecular weights were less crystalline than those prepared in aldehyde, but yet more crystalline than high molecular weight bulk polymer. Polymers prepared in aldehyde had a lower degree of branching than those formed in other transfer agents. It was concluded that aldehyde was effective in increasing the crystallinity of poly(vinyl chloride) in these two ways, and so appeared to be unique among the transfer agents. There was no evidence for assuming any complexing between polymer radicals and aldehyde. |
