Investigation on the organocatalyzed ROP of δ-tetradecalactone: From polymerization to biodegradation

Abstract

Searching for biobased and biodegradable polymers, we explored the organocatalytic ring-opening polymerization (ROP) of a renewable n-alkyl δ-lactone, namely δ-tetradecalactone (δ-TDL) that can be extracted from coconut oil, and we studied the ready biodegradability of the corresponding polyester. As reported for other n-alkyl δ-lactones, 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) was used to perform the bulk and room temperature ROP of δ-TDL. A study of the purification of the monomer prior to its ROP showed the importance of the combination of a distillation process and an elution through basic alumina to remove most of the impurities and obtain the higher molar masses. Despite this careful purification, capped molar masses were obtained (<40 kg/mol) and attributed by NMR and MALDI-ToF spectroscopy to TBD initiation and other side-initiators contained in the monomer, which were not possible to be identified. Other catalysts such as diphenyl phosphate (DPP) and the phosphazene superbase t-BuP4 combined with a thiourea were also tried. The assessment of poly(δ-tetradecalactone) (pTDL) ready biodegradability was finally performed using the OECD test guideline 301F and showed the obtention of up to 41 % biodegradation rate in 28 days using a bioavailability improvement method.