A family of poly­(glycerol sebacate) (PGS) analogues were synthesized by Candida antarctica lipase B (CALB) catalysis to tailor biomaterial properties. Different fractions of glycerol (G) units in PGS were replaced by 1,8-octanediol (O) units. Poly­(glycerol-1,8-octanediol-sebacate), PGOS, synthesized by CALB catalysis with a 1:3 molar ratio of G to O units has M n and M w values of 9500 and 92,000, respectively. PGS undergoes fiber fusion during electrospinning, and cross-linked PGS rapidly resorbs when implanted. By decreasing the molar ratio of glycerol-to-octanediol from 1:1 to 1:4, the peak melting temperature (T m) increased from 27 to 47 °C. PGOS with 1:3 G to O units was electrospun into nanofibers without the need for a second component. The copolymer is semicrystalline and, when cross-linked, undergoes slow in vitro mass loss (3.5 ± 1.0% in 31 days) at pH 7.4 and 37 °C. Furthermore, PGOS cross-linked films have an elastic modulus of 106.1 ± 18.6 MPa, which is more than 100 times that of cross-linked PGS. New PGOS polymers showed tunable molecular weights, better thermal properties, and excellent electrospinnability. This work expanded PGS analogues’ function, making these suitable biodegradable polymers for various biomedical applications.

In order to provide thermodynamic data for mixed dibasic acid separation technology, the solubilities of adipic acid (AA) and succinic acid (SA) in glutaric acid (GA) + acetone mixture and GA + n-butanol mixture were measured by dynamic method at atmospheric pressure. The mass fraction of GA (w GA ) ranged from (0 to 30.11) %. The results show that solubilities of AA and SA in acetone or n-butanol increased with increasing mass fraction of GA in the mixed solvent GA and acetone (or n-butanol) at the same temperature. The ideal solution equation, Apelblat equation, and λh equation were applied to correlation of the experimental solubility data, which were all in good agreement with the three equations. The Apelblat equation is regarded as the best one of the three equations for describing the dissolving of two acids in solvent at the same time.

This study demonstrated that immobilized Candida antarctica lipase B (N435) catalysis in bulk leads to higher molecular weight poly(glycerol sebacate), PGS, than self-catalyzed condensation polymerization. Since the glass-transition temperature, fragility, modulus, and strength for rubbery networks are inversely dependent on the concentration of chain ends, higher molecular weight PGS prepolymers will enable the preparation of cross-linked PGS matrices with unique mechanical properties. The evolution of molecular species during the prepolymerization step conducted at 120 °C for 24 h, prior to enzyme addition, revealed regular decreases in sebacic acid and glycerol-sebacate dimer with corresponding increases in oligomers with chain lengths from 3 to 7 units such that a homogeneous liquid substrate has resulted. At 67 h, for N435catalyzed PGS synthesis, the carboxylic acid conversion reached 82% without formation of a gel fraction, and number-average molecular weight (M n ) and weight-average molecular weight (M w ) values reached 6000 and 59 400 g/mol, respectively. In contrast, self-catalyzed PGS condensation polymerizations required termination at 55 h to avoid gelation, reached 72% conversion, and M n and M w values of 2600 and 13 800 g/mol, respectively. We also report the extent that solvent fractionation can enrich PGS in higher molecular weight chains. The use of methanol as a nonsolvent increased M n and M w by 131.7 and 18.3%, respectively, and narrower dispersity (Đ) decreased by 47.7% relative to the nonfractionated product.

To provide fundamental thermodynamic data for the crystallization separation of succinic acid and adipic acid from mixed dibasic acid, the solubilities of succinic acid in various mass fractions of the adipic acid + glutaric acid + acetone mixture and adipic acid in various mass fractions of the succinic acid + glutaric acid + acetone mixture were measured by the dynamic method at a temperature range of 277.85− 327.95 K under atmospheric pressure. The results showed that the solubility of succinic acid in acetone increased with increasing mass fraction of adipic acid and glutaric acid in the mixed solvent at the same temperature. Similarly, the solubility of adipic acid in acetone increased with increasing mass fraction of succinic acid and glutaric acid in the mixed solvent at the same temperature. The ideal solution equation, Apelblat equation, λh equation, and nonrandom two-liquid (NRTL) equation were applied to correlate the experimental solubility data, which were all in good agreement with the four equations.