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Local chain configuration dependence of the mechanisms of analogous reactions of PVC, 7. Nucleophilic substitution with potassium 2‐ethylhexylthioglycolate and related effects on T g
Author(s) -
Martínez G.,
Millán J.
Publication year - 2000
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/1521-3935(20000901)201:14<1709::aid-macp1709>3.0.co;2-k
Subject(s) - chemistry , nucleophilic substitution , triad (sociology) , steric effects , tacticity , cyclohexanone , potassium , substitution reaction , sodium , polymer chemistry , nucleophile , medicinal chemistry , organic chemistry , polymerization , polymer , psychology , psychoanalysis , catalysis
The nucleophilic substitution reaction of poly(vinyl chloride) (PVC) with potassium 2‐ethylhexylthioglycolate (KEHTG) was performed in a cyclohexanone solution. The evolution of unreacted iso‐, hetero‐ and syndiotactic triad contents with the degree of substitution was observed by means of 13 C NMR spectroscopy. Due to steric hindrance the fraction of mmr tetrads which react occasionally by the central chlorine of the mr triad instead of the mm is smaller than that found previously for sodium benzenethiolate (NaBT) and sodium thiobenzoate (NaTB), but not nil as in the case of sodium 2‐mercaptobenzothiazolate (NaMBT). Correspondingly, the increase in stereoselective character of the reaction as the result of the nucleophile bulkiness is found to approximate to that observed for NaMBT. This conclusion was confirmed on the basis of FTIR results and takes the molecular microstructure‐based mechanisms of substitution of PVC, as discussed in previous work, an important step further. From the evolution of T g with the degree of conversion it follows that T g varies with the degree of substitution in a similar way to the ratio between the extent to which mmr and rrmr structures intervene in the substitution reaction, thereby providing valuable information regarding the T g /microstructure relationship as discussed in recent papers.