Cationic polymerization of α-pinene using Keggin silicotungstic acid as a homogeneous catalyst

Abstract

Cationic polymerization of α-pinene with silicotungstic acid (SiW12) as a catalyst was investigated. The structure of polymers and the catalysts were characterized by FT-IR, 1H-NMR and GPC. The experiments show that SiW12 is more active than both phosphotungstic acid and phosphomolybdic acid. The protons dissociating from the catalysts are the reactive species. SiW12 is found to be both the polymerization initiator and the counter-anion of the growing cationic center. The polymerization conditions are optimized by the single factor method as follows: monomer concentration is 50% (v/v), the dosage of catalysts is 7 wt% referred to α-pinene, reaction temperature is 50 °C, reaction time is 1 h. Under these conditions, the overall conversion of α-pinene is up to 90.87%, the polymer yield is 62.46% and its average number molecular weight is about 600. GC–MS analysis shows that there are six isomers of α-pinene after the reaction, but their content is very low. Most of α-pinene are changed to poly(α-pinene).