Stereoselective nucleophilic substitution of poly(vinyl chloride) with potassium 4‐acetamidothiophenolate

Abstract

The nucleophilic substitution reaction of poly(vinyl chloride) (PVC) with potassium 4‐acetamidothiophenolate was performed in a cyclohexanone solution. The quantitative microstructural analysis, as a function of the conversion, was followed by 13C NMR spectroscopy. Through a comparison of the microstructural changes with the degree of substitution, a small fraction of mmr tetrads was found to react occasionally with the central chlorine of the mr triad instead of the mm, such as for sodium benzenethiolate (NaBT). This conclusion was confirmed by Fourier transform infrared results. However, unlike NaBT, the evolution of the glass‐transition temperature (Tg) with the degree of conversion changed with the degree of substitution similarly to the ratio of the extents to which mmr and rrmr structures intervened in the substitution reaction. From these studies, it followed that the specific interactions due to the polar nature of the nucleophile enhanced the molecular‐microstructure‐based mechanisms, which were responsible for Tg. Such a novel quantitative correlation, compared with more tentative ones obtained previously, presents valuable insight into the role of the stereochemical microstructure in the glass‐transition process in PVC. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1857–1867, 2004

New results on the influence of the nature of the nucleophile in the stereospecific modification of poly(vinyl chloride)

“…The exploration of the nucleophilic substitution reaction of PVC with KAT and NaMBT in CH solution from a kinetic point of view was reported in detail in preceding works 19, 21. Basically, the conversion curve for KAT21 was shown to consist of a quick period followed by a plateau, in accordance with that observed previously with other nucleophiles, e.g., sodium benzenethiolate (NaBT) 18, 20. Conversely, the reaction with NaMBT19 shows an almost linear reactivity from the onset of the reaction.…”

“…Equimolar amounts of NT and potassium carbonate (K 2 CO 3 ) to form 2‐naphthalenethiolate anion in situ in CH were used. KAT and NaMBT were synthesized from the corresponding thiol, as described elsewhere 19, 21…”

“…Substitution reactions with KAT and NaMBT in purified CH were performed according to previously described experimental conditions 19, 21. Substitution reactions of PVC with KNT were performed with the following protocol: 2.0 g (32.0 mmol, based on a monomeric unit) of PVC was dissolved in 83 mL of CH and 4.30 g (31.0 mmol) of K 2 CO 3 , and 5.12 g (32.0 mmol) of NT were added to the polymer solution.…”

“…An extensive research program has been performed in our laboratory to verify the prominent role of the tacticity‐governed microstructure in the mechanisms of analogous reactions of PVC. The conclusions on the dependence of substitution mechanisms on the tacticity‐depending molecular microstructure have been published recently in detail 17–21…”

“…More recently, we studied the substitution reaction of PVC with potassium 4‐acetamidothiophenolate (KAT),21 a nucleophile with the capability of interacting with hydrogen atoms. We found that despite mechanism C, the evolution of the T g with substitution completely agrees with the ratio of mmr to rrmr structures, that is, the specific interactions of the nucleophile–polar nature provides an enhancement of the molecular microstructure‐based mechanisms, which are responsible for the T g .…”