Acyl Poly(Glycerol-Succinic Acid) Oligoesters: Synthesis, Physicochemical and Functional Properties, and Biodegradability

Optimisation of Glycerol and Itaconic Anhydride Polycondensation

Glycerol polyesters have recently become objects of interest in tissue engineering. Barely known so far is poly(glycerol itaconate) (PGItc), a biocompatible, biodegradable polyester. Due to the presence of a C=C electron-acceptor moiety, it is possible to post-modify the product by Michael additions to change the properties of PGItc. Thus, using PGItc as one of the elements of cellular scaffold crosslinked in situ for bone tissue regeneration seems to be a very attractive yet unexplored solution. This work aims to optimize the synthesis of PGItc to obtain derivatives with a double bond in the side chain with the highest conversion rates. The experiments were performed with itaconic anhydride and glycerol using mathematical planning of experiments according to the Box-Behnken plan without solvent and catalyst. The input variables of the process were the ratio of the OH/COOH, temperature, and reaction time. The optimised output variables were: the degree of esterification (EDtitr), the degree of esterification calculated from the analysis of 1H NMR spectra (EDNMR), and the degree of itaconic anhydride conversion-calculation based on 13C NMR spectra (%X13CNMR). In each of statistical models, the significance of the changed synthesis parameters was determined. Optimal conditions are when OH/COOH ratio is equal to 1.5, temperature is 140 °C and time of reaction is 5 h. The higher OH/COOH ratio, temperature and longer the experiment time, the higher the value of the degree of esterification and the degree of anhydride conversion.

Polyglycerol Hyperbranched Polyesters: Synthesis, Properties and Pharmaceutical and Biomedical Applications

In a century when environmental pollution is a major issue, polymers issued from bio-based monomers have gained important interest, as they are expected to be environment-friendly, and biocompatible, with non-toxic degradation products. In parallel, hyperbranched polymers have emerged as an easily accessible alternative to dendrimers with numerous potential applications. Glycerol (Gly) is a natural, low-cost, trifunctional monomer, with a production expected to grow significantly, and thus an excellent candidate for the synthesis of hyperbranched polyesters for pharmaceutical and biomedical applications. In the present article, we review the synthesis, properties, and applications of glycerol polyesters of aliphatic dicarboxylic acids (from succinic to sebacic acids) as well as the copolymers of glycerol or hyperbranched polyglycerol with poly(lactic acid) and poly(ε-caprolactone). Emphasis was given to summarize the synthetic procedures (monomer molar ratio, used catalysts, temperatures, etc.,) and their effect on the molecular weight, solubility, and thermal and mechanical properties of the prepared hyperbranched polymers. Their applications in pharmaceutical technology as drug carries and in biomedical applications focusing on regenerative medicine are highlighted.

Synthesis of Glycerol-Based Biopolyesters as Toughness Enhancers for Polylactic Acid Bioplastic through Reactive Extrusion

The synthesis of polyesters based on glycerol, succinic acid [poly(glycerol succinate), PGS] and/or maleic anhydride [poly(glycerol succinate-co-maleate), PGSMA] was investigated aiming to produce a green product suitable for toughening of polylactic acid (PLA) using melt blending technologies. The molar ratio of reactants and the synthesis temperature were screened to find optimum synthesis conditions leading to the highest toughness enhancement of PLA. It was found that a molar ratio of reactants of 1:1 glycerol/succinic acid increases the effectiveness of PGS as a toughening agent for PLA, which correlates with the achievement of a higher molecular weight on the synthesis of PGS. The introduction of maleic anhydride as a comonomer for the synthesis of the partial replacement of succinic acid was advantageous for making PGS suitable for reactive extrusion (REX) mediated by free radical initiators. The tensile toughness of the REX PLA/PGSMA blends was improved by 392% compared with that of neat PLA, which was caused by the simultaneous cross-linking of PGSMA within the PLA matrix, and the in situ formation of PLA-g-PGSMA graft copolymers acting as interfacial compatibilizers. Two-dimensional nuclear magnetic resonance and Fourier transform infrared analysis confirmed the formation of PLA-g-PGSMA species on REX experiments. This in turn caused a decrease in the diameter of the PGS particles dispersed within the PLA matrix from >10 μm to approximately 2 μm as observed using scanning electron microscopy. A further increase of 1600% in the toughness of the blends was achieved by lowering the synthesis temperature of PGSMA from 180 to 150 °C. The optimum synthesis conditions for PGSMA leading to the highest increase in the toughness of 80/20 PLA/PGSMA blends were found to be 1:0.5:0.5 mol glycerol/succinic acid/maleic anhydride synthesized at a temperature of 150 °C for 5 h.