The stereoregulating effects of aldehydes on the free radical polymerization of vinyl chloride

Abstract

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.

Structural and Dynamic Characterization of Polymers by 13C and 19F NMR

“…The temperature dependence of the stereochemical configuration can be expressed as AH$meso -AHÎracemiC, which has the value 260 cal/mol for polyvinyl chloride and 300 cal/mol for polyvinyl bromide. Polymerization in n-butyraldehyde increases the probability of syndiotactic propagation to a perceptible degree (15). This point is demonstrated in Figure 3 (14), which shows an Arrhenius plot of the configuration of polyvinyl chloride and polyvinyl bromide.…”

The effect of copolymerization on stereoregular polyvinyl chloride

“…The regularity of the polymers was investigated by means of x-ray diffraction and infrared absorption as described in a previous paper. 2 The reduced viscosities of the polymers were determined on 0.1 g. samples of the polymers dissolved in 100 ml. of cyclohexanone.…”

Tacticity as a problem in copolymerization: Influence of neighboring units on reactivity of growing chains

“…where Similarly, Kaaa/Kaab = rl'(r1z + l)/(rI'x + 1) 11 (7) On substitution iii eqs. The above mathematical treabment assumes that reaction occurs under ideal conditions, so that virtually all units in a given chain are added in accordance with the same reactivity ratios.…”