Polymers from renewable sources. III. Hydroxy‐terminated myrcene polymers

Abstract

Abstract A range of hydroxy‐terminated polymyrcenes has been prepared using hydrogen peroxide initiated polymerization of pyroysate grade, β‐myrcene in n ‐butanol solution at 100°C. An oligomeric fraction, containing a large proportion of dimeric material formed via the Diels–Alder reaction, always accompanies the major polymeric fraction. Procedures are described for the removal of this oligomeric material. Polyols so prepared and purified had number average molecular weights ( M n ) between 4000 and 2000 g mol −1 at low and high initiator concentrations, respectively, with corresponding number average functionalities ( f n ) between 1.3 and 2.3 and polydispersities ( M w / M n ) of ∼1.3. The microstructure of the polyols was investigated using NMR spectroscopy from which the main mode of propagation during polymerization of myrcene was deduced to be 1,4 addition across the conjugated double bonds. Glass transition temperatures of the polymyrcenes measured by differential scanning calorimetry were in the range −50–60°C.