Insoluble and Thermostable Polyhydroxyesters From a Renewable Natural Occurring Polyhydroxylated Fatty Acid

To explore the potential of long chain polyhydroxyalkanoates as non-toxic food packaging materials, the characterization of polyesters prepared from a natural occurring polyhydroxylated C16 carboxylic acid (9,10,16-trihydroxyhexadecanoic or aleuritic acid) has been addressed. Such monomer has been selected to elucidate the reactivity of primary and secondary hydroxyl groups and their contribution to the structure and properties of the polyester. Resulting polyaleuritate films have been produced using an open mold in one-step, solvent-free self-polycondensation in melt state and directly in air to evaluate the effect of oxygen in their final physical and chemical properties. These polymers are amorphous, insoluble, and thermostable, being therefore suitable for solvent, and heat resistant barrier materials. Structurally, most of primary hydroxyls are involved in ester bonds, but there is some branching arising from the partial participation of secondary O-H groups. The oxidative cleavage of the vicinal diol moiety and a subsequent secondary esterification had a noticeable effect on the amorphization and stiffening of the polyester by branching and densification of the ester bond network. A derivation of such structural modification was the surface compaction and the reduction of permeability to water molecules. The addition of Ti(OiPr)₄ as a catalyst had a moderate effect, likely because of a poor diffusion within the melt, but noticeably accelerated both the secondary esterification and the oxidative processes. Primary esterification was a high conversion bulk reaction while oxidation and secondary esterification was restricted to nearby regions of the air exposed side of cast films. The reason was a progressive hindering of oxygen diffusion as the reaction progresses and a self-regulation of the altered layer growth. Despite such a reduced extent, the oxidized layer noticeably increased the UV-vis light blockage capacity. In general, characterized physical properties suggest a high potential of these polyaleuritate polyesters as food preserving materials.

Biocatalytic Route for the Synthesis of Oligoesters of Hydroxy-Fatty acids and ϵ-Caprolactone

Developments of past years placed the bio-based polyesters as competitive substitutes for fossil-based polymers. Moreover, enzymatic polymerization using lipase catalysts has become an important green alternative to chemical polymerization for the synthesis of polyesters with biomedical applications, as several drawbacks related to the presence of traces of metal catalysts, toxicity and higher temperatures could be avoided. Copolymerization of ϵ-caprolactone (CL) with four hydroxy-fatty acids (HFA) from renewable sources, 10-hydroxystearic acid, 12-hydroxystearic acid, ricinoleic acid, and 16-hydroxyhexadecanoic acid, was carried out using commercially available immobilized lipases from Candida antarctica B, Thermomyces lanuginosus, and Pseudomonas stutzeri, as well as a native lipase. MALDI-TOF-MS and 2D-NMR analysis confirmed the formation of linear/branched and cyclic oligomers with average molecular weight around 1200 and polymerization degree up to 15. The appropriate selection of the biocatalyst and reaction temperature allowed the tailoring of the non-cyclic/cyclic copolymer ratio and increase of the total copolymer content in the reaction product above 80%. The catalytic efficiency of the best performing biocatalyst (Lipozyme TL) is evaluated during four reaction cycles, showing excellent operational stability. The thermal stability of the reaction products is assessed based on TG and DSC analysis. This new synthetic route for biobased oligomers with novel functionalities and properties could have promising biomedical applications.

Highly efficient strategies toward sustainable monomers and polymers derived from fatty acids via tetramethylguanidine promoted esterification

Three efficient strategies were developed to transform fatty acids into mono-functional monomers and thermoplastic polymers by using 1,1,3,3-tetramethylguanidine promoted esterification.

Toughened aromatic poly-(decylene terephthalate) copolyesters with two renewable eugenol-based components via a random copolymerization method

We synthesized two series of poly-(decylene terephthalate) copolyesters toughened with two renewable eugenol-based components, and the best results belong to PDT80%M120% and PDT80%M220% copolyesters.

Self-assembly of well-defined fatty acid based amphiphilic thermoresponsive random copolymers

Side-chain stearic acid containing thermoresponsive and crystalline random copolymers are synthesized via RAFT technique, which self-assembled to spherical micellar structures in aqueous solution depending on stearate content in the copolymer.

Facile and Highly Efficient Strategy for Synthesis of Functional Polyesters via Tetramethyl Guanidine Promoted Polyesterification at Room Temperature

A facile and highly efficient strategy for the synthesis of functional polyesters from 10-undecenoic acid, which is abundantly available and derived from ricin oil, has been successfully achieved using 1,1,3,3-tetramethyl guanidine (TMG) as a promoter at room temperature. The experimental results indicate that high molecular weight polyesters have been obtained and a variety of functional groups, such as alkenyl, alkynyl, nitro, epoxy, hydroxyl, and bromoisobutyrate, can be incorporated as pendant groups. The structures of the obtained polymers were demonstrated by ¹H and ¹³C NMR spectroscopy and their thermal properties were studied by DSC and TGA.

Controlled RAFT synthesis of side-chain oleic acid containing polymers and their post-polymerization functionalization

We report the synthesis and characterization of well-defined polymers from oleic acid as the bio-renewable resource. Double bonds in oleate side-chains in the polymer are further modified by thiol-ene reaction, epoxidation, and cross-linking.