Carbon dioxide offers an accessible, cheap and renewable carbon feedstock for synthesis. Current interest in the area of carbon dioxide valorisation aims at new, emerging technologies that are able to provide new opportunities to turn a waste into value. Polymers are among the most widely produced chemicals in the world greatly affecting the quality of life. However, there are growing concerns about the lack of reuse of the majority of the consumer plastics and their after-life disposal resulting in an increasing demand for sustainable alternatives. New monomers and polymers that can address these issues are therefore warranted, and merging polymer synthesis with the recycling of carbon dioxide offers a tangible route to transition towards a circular economy. Here, an overview of the most relevant and recent approaches to CO2-based monomers and polymers are highlighted with particular emphasis on the transformation routes used and their involved manifolds.

Advances in the use of CO2 as a renewable feedstock for the synthesis of polymers

A synthetic strategy was developed for the condensation polymerization of aliphatic diols with dimethyl carbonate to produce high-molecular-weight aliphatic polycarbonates. In the first step, oligomers were formed bearing almost equal numbers of hydroxyl and methyl carbonate end-groups. In the second step, the condensation reaction was conducted at a high temperature (>180 °C) to connect the −OH and −OC(O)OCH3 chain-ends while removing the generated methanol under reduced pressure. Small amounts of sodium alkoxide (0.02–0.5 mol %) were used as a catalyst. Using an anhydrous diol was crucial for increasing the reaction rate and also for obtaining reproducible results. In the second step, the pressure was gradually reduced and the temperature was optimized, in order to minimize side products. Using this strategy, high-molecular-weight poly(1,4-butylene carbonate) (PBC) and its copolymers incorporating various other diols (2–10 mol %) were prepared, with weight-average molecular weight (Mw) of 100 000–200 00...

Preparation of High-Molecular-Weight Aliphatic Polycarbonates by Condensation Polymerization of Diols and Dimethyl Carbonate

Conventional production of aromatic polycarbonates (PCs) involves interfacial polycondensation between phosgene (COCl2) and bisphenol A (BPA). This COCl2 process has several drawbacks such as environmental and safety problems involved in using the highly toxic COCl2 as the reagent, which resulted in the formation of chlorine salts of a stoichiometric amount, and in using copious amounts of methylene chloride as the solvent. For these reasons, environmentally friendly processes for PC production without COCl2 have been developed such as melt transesterification of BPA and diphenyl carbonate (DPC). However, COCl2-free production of DPC is not easy yet because of its severe equilibrium constraint, and therefore obtaining DPC efficiently is the most important step to develop a successful COCl2-free PC process. DPC can be obtained via two methods without using COCl2:  two-step synthesis of DPC from dimethyl carbonate (DMC) and phenol and direct oxidative carbonylation of phenol. The DPC reacts with BPA to form...

Making Polycarbonates without Employing Phosgene: An Overview on Catalytic Chemistry of Intermediate and Precursor Syntheses for Polycarbonate

The effect of thermodynamic phase equilibrium on the kinetics of semibatch melt polycondensation of bisphenol-A and diphenyl carbonate was studied for the synthesis of polycarbonate. In the melt-polymerization process, a partial loss of diphenyl carbonate occurs as the reaction by-product phenol is removed from the reactor. To obtain a high molecular weight polymer under high temperature and low-pressure conditions, a stoichiometric mol ratio of the two reactive end groups needs to be maintained during the polymerization. In this work, vapor–liquid equilibrium data for a binary mixture of phenol and diphenyl carbonate are reported and they are used in conjunction with the Wilson equation to calculate the exact amounts of diphenyl carbonate and phenol returned from a reflux column to the reactor. A good agreement between the reactor model simulations and the experimental polymerization data was obtained. It was also observed that diphenyl carbonate is quickly consumed during the early stage of polymerization and the fraction of evaporated diphenyl carbonate refluxed to the reactor is essentially constant during this period. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1253–1266, 2001

Melt polymerization of bisphenol‐A and diphenyl carbonate in a semibatch reactor

Step-growth polymers are produced by the reactions of functional groups of monomers in a stepwise progression from dimers, trimers, etc. to eventually form high polymer. When this polymerization process is accompanied by the elimination of small molecules during the reaction step, the process is called polycondensation. This chapter reviews the basics of the chemistries that govern the build-up of molecular weight in step-growth polymerizations. This is followed by summary discussions on the major classes of step-growth polymers such as polyesters, polycarbonates, polyamides, polyurethanes, and polyimides. Other step-growth polymers such as poly (arylene ethers), polyketones, and polysulfones are also important commercially, but are not discussed in this chapter. Although high molecular weight is often required for the maximization of thermal and mechanical properties, the synthesis of difunctional oligomers (less than 10,000 g/mole) is accomplished in step-growth polymerization using mono functional reagents or a stoichiometric excess of a difunctional monomer.

Step-growth polymerization

The kinetics of batch melt transesterification of diphenyl carbonate with 2,2-bis(4-hydroxyphenyl)propane to polycarbonate have been studied in the presence and absence of LiOH.H 2 O catalyst in the temperature range of 180-250 o C. The effects of reaction temperature and catalyst concentration on conversion and oligomer formation are analyzed. For quantification of the reaction kinetics, a detailed molecular species model has been developed and solved. Quite satisfactory agreement between the model predictions and experimental data has been obtained

Kinetics of melt transesterification of diphenyl carbonate and bisphenol A to polycarbonate with lithium hydroxide monohydrate catalyst

A multistage melt polycondensation of bisphenol-A and carbonate has been studied experimentally using LiOH·H2O catalyst. The reaction process consists of batch and semi-batch periods with different temperature and pressure conditions. It was observed that a small amount of diphenyl carbonate lost from the reaction mixture by vaporization had little effect on the molecular weight in the batch reaction period but the efficiency of subsequent low-pressure semibatch polycondensation was affected by the change in the mol ratio of the phenyl carbonate group to the hydroxyl end group. A molecular species model developed for the multistage process was used to analyze the kinetics of the polycondensation process. The composition of the reaction mixture was analyzed of HPLC and compared with model simulations. In particular, the effect of evaporative loss of diphenyl carbonate on the progress of reaction is discussed in detail. © 1993 John Wiley & Sons, Inc.

Yangsoo Kim

Papers

Kinetics of melt transesterification of diphenyl carbonate and bisphenol A to polycarbonate with lithium hydroxide monohydrate catalyst

Multistage melt polymerization of bisphenol‐A and diphenyl carbonate to polycarbonate