Making Aliphatic Degradable Polycarbonates Using CO₂

Researchers have developed the first metal-free process for making aliphatic degradable polycarbonates using CO2. Professors Yves Gnanou and Nikolaos Hadjichristidis from KAUST along with their fellow researchers have developed the first metal-free process for making aliphatic degradable polycarbonates using CO₂.

Plastics are good in terms of elasticity, flexibility, tensile strength and recyclability. These qualities of plastics can also be manipulated in order to obtain a material that can be used in various applications. The overuse of plasticshas caused a harmful effect on the environment and most importantly damage to the oceans.With the ever increasing use of plastics as well as great amount of CO₂ emissions into the atmosphere, there is a lot of global warming taking place. There is an urgent need to reduce plastic consumption and encouraging reuse.

In 1969, some Japanese chemists from the University of Tokyo successfully synthesized a polycarbonate using CO₂. Over the years, researchers have been refining the catalytic process of combining CO₂ with epoxides making use of transition metals to give polymeric materials. There was not much success commercially.

China has taken the lead in making aliphatic degradable polycarbonates using CO₂ on a commercial scale. Making of aliphatic degradable polycarbonates using CO₂ and using them in food packaging, plastic shopping bags and as a protective covering in the case of agricultural applications is being done by China on a commercial scale. In order to reduce emissions, China has been using polycarbonates made from CO₂.

Novomer, a US company that is making aliphatic degradable polycarbonates using CO₂ was acquired by Saudi Aramco in 2016. November and the factories in China use metal-based catalysts for this process.

Making aliphatic degradable polycarbonates using CO₂ and non-metal as a catalyst

Gnanou and his research team have developed a process of doing away with toxic metals as catalysts. They have used two non-metallic reactants. One is an ammonium compound which helps the coupling reaction between CO₂ and epoxides and the other a boron-based compound which activates the latter monomer.

Advantage of making aliphatic degradable polycarbonates using CO₂ with non-metal catalyst

When using metals as catalysts, the problem that arises is the toxicity and the colour of the material. In case polycarbonates are made for food applications, then this could be harmful. It is necessary for the metal to be removed and this could be energy and resource intensive. In addition, if any metal is present in the polycarbonate, then it could result in the degradation in the material.

There was an Intergovernmental Panel set up to discuss climate change. They released a report stating that global warming should be kept to 1.5 degrees Celsius to prevent any further damage to the ecosystem. In addition, the carbon dioxide emission had to reduce by 45 percent from the 2010 level by the year 2030 and to zero by 2050.

According to Professor Yves Gnanou form KAUST, CO₂ should be used to make polymers. In this way CO₂ can be harnessed and used up instead of damaging the environment. He is keen that the rest of the world follow China in making aliphatic degradable polycarbonates using CO₂ and take action thereby harnessing CO₂.