Carbon Materials and Technology
Debashis Chakraborty; Sourav Singha Roy; Sriparna Sarkar
Abstract
The production of aliphatic polyesters (via ROP of cyclic esters) and aliphatic polycarbonates (via ROCOP of CO2/epoxide) is an important synthetic pathway for the production of biodegradable and biocompatible polymers. The study focuses on the catalytic activity and selectivity of phenoxy-imine based ...
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The production of aliphatic polyesters (via ROP of cyclic esters) and aliphatic polycarbonates (via ROCOP of CO2/epoxide) is an important synthetic pathway for the production of biodegradable and biocompatible polymers. The study focuses on the catalytic activity and selectivity of phenoxy-imine based zinc compounds for the ROP of cyclic esters (rac-LA and -CL) and ROCOP of carbon dioxide and CHO/PO. The monoligated and bisligated zinc compounds have the same coordination number (four) but differed from each other in the binding mode of the ligand to the metal center (tridentate for monoligated and bidentate for bisligated compounds) and thus the compounds adopt different symmetry. For the ROP of rac-LA, the monoligated zinc compounds gave isotactic-enriched PLA while the bisligated zinc compounds gave heterotactic-enriched PLA. For the ROCOP of epoxide/CO2, isotactic-enriched polycarbonates were obtained with a notable difference in catalytic activity with the variation of the number of ligands attached to the zinc center. In addition, a correlation is established between the percentage of carbonate linkage in the polycarbonate chain and the substituent attached to the phenolate core.
Asutosh Kumar Pandey
Abstract
Zinc salts of L-proline, D-proline were used in homopolymerization of L, L-lactide and D, L-lactide. Linear PLA oligomer with Mn 2900-3400 Da, can be prepared with zinc (L-prolinate)2 catalyst. Less racemization were occurred in presence of Zn (L-prolinate)2 than Zn (D-prolinate)2. The catalyst structure ...
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Zinc salts of L-proline, D-proline were used in homopolymerization of L, L-lactide and D, L-lactide. Linear PLA oligomer with Mn 2900-3400 Da, can be prepared with zinc (L-prolinate)2 catalyst. Less racemization were occurred in presence of Zn (L-prolinate)2 than Zn (D-prolinate)2. The catalyst structure of Zn (L-prolinate)2 and Zn (D-prolinate)2 remains intact after polymerization. The zinc is bioactive molecule so these polymers prepared by using this catalyst are bioabsorbable. The resulting polymers were characterized by infrared spectroscopy (IR), size exclusion chromatography (SEC), differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA), 13 C NMR, 13 C Cross Polarization /Magic Angle Spinning ( 13 C CP/MAS) and MALDI ToF-MS.