Effect of a phase-transfer catalyst on the chemical modification of poly(vinyl chloride) by substitution with thiocyanate as a nucleophile

This study examined the effect of the phase-transfer catalysts tetrabutylammonium bromide (TBAB) and tetrabutylammonium hydrogen sulfate (TBAHS) on the chemical modification of poly(vinyl chloride) (PVC) by substitution with thiocyanate as a nucleophile. TBAB accelerated the dechlorination of PVC in SCN/ethylene glycol (EG) solution. Furthermore, the addition of TBAB to SCN/EG solution improved the substitution of the Cl in PVC with SCN in solution. The addition of TBAB or TBAHS to SCN/H₂O solution promoted the dechlorination of PVC, whereas dechlorination did not occur without the catalyst. The catalysts preferred substitution to the elimination of HCl in SCN/H₂O solution, and TBAB was slightly superior to TBAHS in terms of the degree and selectivity of the substitution. The addition of nitrobenzene to SCN/H₂O solution with TBAB increased the degree of substitution. Consequently, phase-transfer catalysts, particularly TBAB, were very effective at promoting the substitution of Cl in PVC with SCN in solution.