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Study of stereoregularity of poly(vinyl ketone)s by proton nuclear magnetic resonance
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AbstractTwo poly(vinyl ketone)s, poly(methyl vinyl ketone) (PMVK) and poly(phenyl vinyl ketone) (PPVK), are isotacticly synthesized. The 1H‐NMR spectra of these polymers and of the meso and racemic model dimers help to determine the percentage of isotactic dyads using the area of the peaks of the non equivalent protons (HA and HB) of the β‐methylene group of the chain. The difference between the chemical shifts of the HB and HB protons is exceptionally large (approximately 0,8 ppm for both isotactic PMVK and isotactic PPVK). The coupling constants and the β‐CH2 and the α‐CH groups' frequencies are determined by applying the ABX2 system.A spontaneous epimerization of isotactic PPVK is found; this is always accompanied by a degradation and leads to the assumption of a simultaneous photochemical reaction of the Norrish II type.
Title: Study of stereoregularity of poly(vinyl ketone)s by proton nuclear magnetic resonance
Description:
AbstractTwo poly(vinyl ketone)s, poly(methyl vinyl ketone) (PMVK) and poly(phenyl vinyl ketone) (PPVK), are isotacticly synthesized.
The 1H‐NMR spectra of these polymers and of the meso and racemic model dimers help to determine the percentage of isotactic dyads using the area of the peaks of the non equivalent protons (HA and HB) of the β‐methylene group of the chain.
The difference between the chemical shifts of the HB and HB protons is exceptionally large (approximately 0,8 ppm for both isotactic PMVK and isotactic PPVK).
The coupling constants and the β‐CH2 and the α‐CH groups' frequencies are determined by applying the ABX2 system.
A spontaneous epimerization of isotactic PPVK is found; this is always accompanied by a degradation and leads to the assumption of a simultaneous photochemical reaction of the Norrish II type.
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