Local chain configuration dependence of the mechanisms of analogous reactions of PVC. II. A further evidence through the changes in conformationally sensitive FTIR bands with degree of nucleophilic substitution

Abstract

The evolution of the ν C (SINGLE BOND) Cl bands of the infrared spectrum of a Bernoullian though slightly isotactic poly(vinyl chloride) (PVC), with both the degree of SN2 substitution reaction with sodium benzenethiolate, as studied earlier, and the increase of the nucleophile infrared bands, has been studied by FTIR spectroscopy. In a parallel way, the changes in the same bands, in particular those at 615 and 637 cm−1, presumably induced by SN2 substitution, have been estimated, theoretically, by comparing the sequential order and the number of the distinct conformationally sensitive vibration modes of C(SINGLE BOND)Cl bond, prior and after substitution, for a series of polymer sequences containing the reactive sites, namely the isotactic mmr tetrad and the heterotactic rmrr pentad, according to earlier work. The experimental behaviour of the νC(SINGLE BOND)Cl bands is found to be in close agreement with the theoretical expectations, thereby allowing two main conclusions to be drawn: (i) during the early stage going up to conversions of 10–12%, the reaction proceeds in a nearly exclusive manner, by the mmr and rmrr terminal of long isotactic and syndiotactic sequences, respectively; and (ii) any reaction event throughout the substitution process proves to be highly dependent upon the local environment in which each of the foregoing reactive structures finds itself. In summary, the local configurational nature of the mechanisms of analogous reactions of polymers is strongly suggested on the grounds of the results given herein. © 1996 John Wiley & Sons, Inc.

Stereoselective Nature of Graft Copolymers Based on Poly(vinyl chloride): Synthesis of PVC-g-PMMA and PVC-g-PIB

“…Consequently, and within experimental uncertainties, an increase in the absorbance ratio A 615cm À1 /A 637cm À1 with the graft copolymerization can be appreciated particularly in the PVC-g-PIB copolymer, in a similar way as in the stereoselective nucleophilic reaction. [38,46] Since after graft copolymerization a few substitutions of C-graft groups for C1Cl groups in the chain of PVC located at mmmr pentad take place, the reactivity of the remain C1Cl in the copolymer will decrease seriously in a further nucleophilic substitution reaction, i. e. with NaBT. [35] Consequently, the reactivity increases as follows: virgin PVC A PVC-g-PMMA (9.8%) A PVC-g-PIB (22.2%) A PVC-g-PIB (75.2%), cf.…”

Synthesis of PVC-graft-PMMA Through Stereoselective Nucleophilic Substitution on PVC

“…By inspection, the following conclusions may be drawn: i) no change in position of the 615 cm -1 and 637 cm -1 bands is noted and ii) the intensity of the band at 615 cm -1 compared to that of the 637 cm -1 increases; furthermore, it becomes narrower and more symmetrical. These peculiarities agree with those found for other nucleophiles, and, as extensively argued elsewhere, [33,34,36] are consistent with the occurrence of mechanism A, exclusively or to the greatest extent. These results are more significant as they relate to a very short range of conversion (0-2%).…”

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

“…The results obtained for the same reaction in the melt state are displayed in Figure 3. Interestingly they are qualitatively similar to those in solution, which, in the light of earlier work on this sort of substitution,13,14,16 gives support to the straight relation between ageing and GTTG–TT conformation as inferred from Figure 2. It was actually found that the substitution reaction in the melt state proceeds most frequently by that conformation despite the severe reaction conditions utilised, namely high temperature and strong shearing forces 15.…”