Abstract
Polylactide (PLA) represents one of the most promising biomedical polymers due to its biodegradability, bioresorbability and good biocompatibility. This work highlights the synthesis and characterization of PLAs using novel diethylzinc/gallic acid (ZnEt2/GAc) and diethylzinc/propyl gallate (ZnEt2/PGAc) catalytic systems that are safe for human body. The results of the ring-opening polymerization (ROP) of rac-lactide (rac-LA) in the presence of zinc-based catalytic systems have shown that, depending on the reaction conditions, “predominantly isotactic”, disyndiotactic or atactic PLA can be obtained. Therefore, the controlled and stereoselective ROP of rac-LA is discussed in detail in this paper.
Highlights
Polymeric biomaterials signify one of the most interesting fields in current material chemistry
We reported that when ring-opening polymerization (ROP) of CL was carried out in the presence of ZnEt2/PGAc catalytic system at 40–60 ̋C within 48 h or at 80 ̋C within 6 h, macrocyclic products did not formed [40]
We described for the first time the synthesis and characterization of polylactides obtained in the presence of two zinc-based catalytic systems
Summary
Polymeric biomaterials (aliphatic polyesters, polyanhydrides, polyethers, polyamides, polyorthoesters or polyurethanes) signify one of the most interesting fields in current material chemistry. For a polyester obtained in the presence of ZnEt2/PGAc catalytic system (60 ̋C within 16 h, Table 3), the calculated coefficient of stereoselectivity p2 was 0.58 (PLA 25), whereas the average length of lactyl units Li = 3.38 (when no ss sequences were present in the polymer chain, this coefficient may be defined as p2 = 2/Li, where Li is the average length of the isotactic microblocks). In the 13C-NMR spectra of PLA obtained in the presence of ZnEt2/PGAc catalytic system (40 ̋C within 16–48 h or 60 ̋C within 16–24 h), no lines due to tetrads and hexads containing the ss sequences were present (Figures 2 and 3). Scheme 33..ThTehheyphoytphoetihceatlimcaelcmhaencihsmanoisfmROoPf oRfOraPc-LoAf rinact-hLeApriensetnhcee pofreZsneEntc2e/GoAf cZannEdtZ2/nGEtA2/cPGanAdc ZcantEalty2/tiPc GsyAsctecmatsa.lytic systems
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