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.
Material Processing
Sourav Singha Roy; Sriparna Sarkar; Debashis Chakraborty
Abstract
The limited availability of fossil fuels on the Earth has led researchers to develop new materials that are derived from renewable feedstocks. The polymers produced from the ROP of cyclic esters like (LA and ɛ-CL) are biodegradable, biocompatible, and bioassimilable and thus find major applications ...
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The limited availability of fossil fuels on the Earth has led researchers to develop new materials that are derived from renewable feedstocks. The polymers produced from the ROP of cyclic esters like (LA and ɛ-CL) are biodegradable, biocompatible, and bioassimilable and thus find major applications in various field. The ROP are catalyzed by the metal-based organometallic catalyst and metal-free organocatalyst. This review exemplifies the living and immortal ROP. The advantage of such polymerization is that they produce polymers with controlled molecular weight distribution. For the immortal ROP, more than one polymer chain grows from the single catalytic site in the presence of chain transfer agents (CTAs), and thus catalyst loading is low, which make the process economically more viable. The nature of CTAs and loading of CTAs with respect to the catalyst is crucial as the catalyst should be effective in the presence of CTAs. The review also discusses functionalized CTAs employed for the polymerization in some instances where functionalized polymers are generated.