The discovery has been made that when vinyl chloride is polymerized in certain aldehydes, a highly crystalline polyvinyl chloride is obtained. In butyraldehyde, low yields of a range of low molecular weight polymers are produced. Elemental analyses showed that they may be characterized by the formula:
where n = 6‐26. Support for this structure and molecular weight range was obtained from infrared and x‐ray examinations of the polymers. The polymers are highly crystalline, as demonstrated by the x‐ray and infrared results, and appear to have a syndiotactic structure. Variation of the polymerization temperature produced no measurable effect on the polymer stereoregularity. The ability of substituted aliphatic aldehydes to produce stereoregular PVC has shown a dependence on the electronegativity of the substituent in the aldehyde. Aliphatic aldehydes with an electron‐releasing α‐methyl group appear to give a more highly crystalline PVC. Aliphatic aldehydes with electron‐withdrawing chlorine and oxygen atoms gives less crystalline PVC than do the corresponding α‐methyl aldehydes. The dependence of the results upon polar effects suggests that the stereoregulating mechanism of the aldehydes involves association between the aldehyde, as a donor molecule, and the free propagating species, as the acceptor radical.
A study was made of the polymerization of vinyl chloride using radioactive NaHS35O3 and KCl36O3 in a redox catalyst system. The object was to determine the fate of the catalysts as an aid to understanding part of the process of radical production and of the initiation of the polymerization. With the catalyst concentration usually used to conduct polymerizations, 0.3 atom of catalyst sulfur and about 0.08 atom of catalyst chlorine are chemically bound per PVC molecule. Increasing the catalyst concentration causes an increase in both the catalyst sulfur and catalyst chlorine incorporated into the PVC. The incorporation of the catalyst sulfur into the PVC, and the role of the sulfite in initiating the polymerization, can be explained by the free radical mechanism postulated for the addition of bisulfite to olefinic bonds. Only one‐tenth of the catalyst chlorine bound to the PVC comes from the hypochlorite intermediate formed during the reaction. This suggests that the reactions of the sulfite with the chlorate, and with the chlorite formed during the reaction, produce most of the chain‐initiating radicals.
Polychloral diol, unlike polyoxymethylene diol, is not readily capped in the presence of alkali catalysts. Polychloral is capped under acid conditions by acid anhydrides and chlorides and does not appear to undergo degradation during the process. Evidence for end‐capping is provided by infrared analysis in the case of the low DP polychloral, metachloral. End‐capped polychlorals possess good stability towards hot dimethylformamide and good stability at elevated temperatures (255°C.). From the melting points of copolymers, polychloral itself is estimated to have a melting point of about 460°C. The high melting point is consistent with the rigidity of the polymer chain. A means of estimating the DP of the polymer is proposed, based on a form of endgroup analysis. By this technique, metachloral is estimated to have a DP of about 50.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.