Terpene-Based Renewable Monomers and Polymers via Thiol-Ene Additions

Solvent and radical initiator-free addition of thiols to terpenes ((R)-(+)- and (S)-(-)-limonene and (-)-beta-pinene) are described as a simple approach to obtain a wide range of alcohol and/or ester functionalized renewable monomers. (R)-(+)-Limonene (1) and (S)-(-)-limonene (2), presenting different reactivity at the endocyclic and exocyclic double bonds, have yielded the mono-addition or diaddition product by simple variation of the thiol feed ratio. In the same manner, (-)-beta-pinene (3) derived alcohol and ester monomers have been prepared. The monomers thus obtained have been characterized, and their behavior in polycondensation has been studied. It has been found that long chain diesters or diols, which were synthesized from a castor oil derived platform chemical, are suitable comonomers and result in polycondensates with number-average molecular weights of up to 25 kDa. Thus, terpene/fatty acid-based polyesters were prepared, and their structure-thermal property relationships were studied.