Correlation between the tacticity and content of labile nondefect structures in poly(vinyl chloride)

Abstract

The content of mm isotactic triads taking the GTTG− conformation for samples of poly(vinyl chloride) (PVC) fractions of different tacticities was measured through a substitution reaction with sodium benzenethiolate. This quantity changed linearly with the ratio of rmmmrx to mmmmrx (x = m or r), as accurately determined by 13C NMR spectroscopy. In a comparison of this correlation and that obtained between the thermal degradation stability and overall isotactic content, as studied previously, some novel evidence for the GTTG− conformation of a few mm triads, termini of isotactic sequences no shorter than one heptad as specific labile sites in PVC, was obtained. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3944–3949, 2002

Principles of Thermal Degradation

“…254 On the other hand, the crosslinking reactions occur under aerobic and anaerobic conditions. During photooxidation, the oxidation occurs in the vicinity of the double bond, resulting in chain scission.…”

Formation of crystalline inclusion compounds of poly (vinyl chloride) of different stereoregularity with γ‐cyclodextrin

“…The mmmmrx ( x = m , r ) heptad content is, as expected, markedly higher as the isotactic content increases, and the population of the g + ttg − conformation (one of the conformations within the mm sequence) must increase in a parallel way. In this respect, some previous experiments show a linear correlation between the g + ttg − conformation and the rmmmrx/mmmmrx ratio 36. The difference in both the mmmr content and rmmmrx/mmmmrx ratio (Table 1) for the samples used in this work, is not very high, but significant enough for analyzing the influence of stereoregularity in the formation of ICs of PVC with γ‐CD and the organization and properties of the samples coalesced from them, which is the purpose of this research.…”

A Local Chain Conformation‐Based Approach to Physical Ageing Fundamentals of Poly(vinyl chloride)

“…As aforementioned, the content of GTTG–TT conformation is of particular importance. It could be estimated by stereoselective substitution reaction at very low temperature where the conformational equilibrium is hardly operative 18,19. The values so obtained from samples X, Y, and Z are also given in Table 1.…”