A new polyester poly(glycerol butenedioate) (PGB) was obtained in the bulk polycondensation of glycerin and maleic anhydride. Glycerol polyesters are new biomaterials commonly used in tissue engineering. PGB, containing the α,β-unsaturated moiety, could be very interesting due to potential modifications such as additions or oxidation. Such modifications are not possible on the heretofore known glycerol polyesters due to their structure without α,β-unsaturated moieties. In this work, the developed process was optimized by applying the design of experiments. The optimization criterium was the minimization of the E/Z isomer ratio. Applying the two-stage process, the E / Z isomer ratio was reduced from 5.5 to 0.5 compared to the one-stage process. The degree of branching was also reduced from 17 to 9%, as well as the degree of esterification from 0.89 to 0.72. The obtained structure can be used in modifying or cross-linking via Michael additions.
Recently intensive development of tissue engineering has been noticeable. It has caused a considerable rise in scientists' interest in biomaterials, which build scaffolds. Beneficial are biocompatible and biodegradable polymers. Due to its structure, poly(glycerol maleate) (PGMal) can be such a material. The structure of this polymer has a reactive double bond group on which precious modification reactions can occur. This article aimed to optimize the process of cross‐linking PGMal using triethylenetetramine. The reaction was investigated without and with a solvent. Due to the high viscosity of the polymer, it was decided to carry out the optimisation in the solvent variant (in tetrahydrofuran). A central, compositional, two‐component plan was used to optimize the process. The optimizing value was the degree of conversion, calculated based on the proton nuclear resonance spectrum. Its maximization was sought. High‐conversion rates were obtained during the tests. The aza‐Michael addition turns out to be a priceless reaction to modify unsaturated polyesters. Selectivity is noticeable in solvent‐free variants. Complete substitution to maleic fragments and partial substitution to fumaric fragments was observed. No selectivity was observed in the presence of THF.
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.
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