Polyesters Inspired by Glycerides: Enzymatic Polycondensation, Structure, Properties, and Nanoparticle Preparation

Abstract

The polycondensation of glycerol and aliphatic dicarboxylic acids catalyzed by Candida antarctica lipase B absorbed on a macroporous acrylic resin (CALB) results in polyesters composed of repetitive units structurally similar to mono-, di-, and triglycerides. Adipic, suberic, sebacic, and dodecanedioic acids were investigated for the CALB-catalyzed polycondensation with glycerol in solution and bulk. In both conditions, the CALB-catalyzed esterification of primary hydroxyl of glycerol and acyl migration occurs in parallel and results in branched polyesters. Higher molar mass polyesters were obtained in reactions performed in bulk and using longer diacids than in solution and using shorter diacids. These glyceride-like polyesters have different amphiphilicity and physical properties that change from more hydrophilic and amorphous for poly(glycerol adipate) to more hydrophobic and semicrystalline for poly(glycerol dodecanedioate). The amphiphilicity of these polyesters allowed the production of nanoparticles with a hydrodynamic radius in the range of 35–270 nm and a negative zeta potential.

Phosphorylated Polyesters Inspired by Phospholipids: Synthesis, Characterization, and Potential Applications

“…The amorphous polyesters PPGAd, PPGSu, and PPGSe present T g in the range from −43 to −36 °C, whereas T g of the semicrystalline PPGD is increased to −8 °C because of the presence of a crystalline phase . The values of T g for each phosphorylated polyester are higher than those reported for the hydroxylated PGAd, PGSu, PGSe, and PGD, equal to −64, −58, −21, and −15 °C, respectively . Two factors influence the T g of phosphorylated polyesters: intra- and intermolecular interactions and the presence of bulky phosphate groups along the polymer chains.…”

“…For the phosphorylated polyesters, the higher T g compared with the corresponding hydroxylated polyesters can be due to the higher density of intra- and intermolecular. The PPGD presents lower T c = 4 °C and T m = 22 °C and smaller Δ H c and Δ H m of around 22–23 J g –1 compared to the corresponding hydroxylated PGD, which presents T c = 24 °C, T m = 45 °C, and Δ H c and Δ H m of around 38–45 J g –1 . Also, PPGSe is amorphous, whereas the hydroxylated PGSe is semicrystalline .…”

“…In bulk, the occurrence of condensation between phosphates and/or hydroxyl groups in anhydrous conditions at T > 100 °C resulted in brittle materials. On the basis of these results, the phosphorylated polyesters were synthesized in a two-step chemoenzymatic route (Figure ) comprising the (i) synthesis of hydroxylated polyesters via CALB-catalyzed polycondensation of glycerol and dicarboxylic diacids in bulk at 80 °C for 24 h under nitrogen flow followed by the (ii) phosphorylation of the hydroxylated polyester using POCl 3 /Et 3 N in THF solution. , …”

“…Thereby, the 1 H and 13 C NMR spectra (Figure b; Figures S1c and S2b) are complex because of the presence of multiple overlapped peaks. For the signal assignment of the 1 H and 13 C NMR spectra and elucidation of the structure of the phosphorylated polyesters, we propose a methodology to calculate the chemical shift of the signals from the protons and carbons of the methine (CH) and methylene (CH 2 ) groups of the repetitive units in the 1 H and 13 C NMR spectra, respectively, based on the model reported by Zhang et al The model considers the changes in the chemical shift of protons and carbons of the CH and CH 2 groups of glycerol due to the substitution effect and their additivity. − It is assumed that the functionalization “j” of a given hydroxyl of glycerol with an ester, in the case of hydroxylated polyesters, and/or with a phosphate group for phosphorylated polyesters results in a constant change of the chemical shift (Δδ j , eq ) of the signals of protons and carbons of the CH and CH 2 groups relative to the respective signals of the glycerol due to the substitution effect. Successive functionalization of the hydroxyls of glycerol results in an overall change in the chemical shift that is equal to the sum of all substitution effect contributions on a given repetitive unit (ΣΔδ j , eq ).…”

“…The polycondensation was performed as reported elsewhere . In a typical procedure, 5.0 mmol of dicarboxylic acid (adipic, suberic, sebacic, or dodecanedioic acid), 5.0 mmol (0.46 g) of glycerol, and 200 mg of CALB for sebacic and dodecanedioic acids or 400 mg for adipic and suberic acids were added in a 30 mL capped glass flask . The reaction was maintained under gentle magnetic stirring (150 rpm) at 80 °C for 24 h under a nitrogen flow.…”