Synthesis of Unsaturated Polyesters Using Itaconic Acid and Biobased Diols and Their Use to Fabricate Fully Biobased Polyester Microcapsules Encapsulating Fragrance Oil

Biobased polyester microcapsules encapsulating fragrance oil were synthesized. Polycondensation of itaconic acid (IA) with ethylene glycol (EG) and isosorbide (ISB) generated EG- and ISB-based unsaturated polyesters, UPE-EG and UPE-ISB, respectively, which contained polymerizable vinylidene groups (IA units) on the backbone. UPE-EG and UPE-ISB were used as polymerizable components in oil-in-water emulsions to form microcapsules. The polymerizable components located at the oil-water interface were polymerized via interfacial radical polymerization to generate microcapsules. IA, EG, and ISB are renewable, and hence the resultant microcapsules are fully biobased. The key to synthesizing microcapsules with robust (dense) polymer shells was to efficiently deposit UPEs at the oil-water interface for interfacial polymerization (crosslinking). UPE-EG was initially dispersed in the aqueous phase in the emulsion. UPE-EG was relatively hydrophobic and effectively diffused from the aqueous phase to the oil-water interface during the polymerization, resulting in efficient deposition at the interface. In contrast, UPE-ISB was initially dispersed in the oil phase in the emulsion. UPE-ISB was relatively hydrophilic and effectively diffused from the oil phase to the oil-water interface, resulting in efficient deposition at the interface. Thus, by controlling the initial location of UPE-EG and UPE-ISB in the aqueous and oil phases, the microcapsules were successfully obtained.