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.
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