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Fig. 1. Graphic demonstration of a method developed by chemists from the University of Batsk to convert carbon dioxide and carbohydrates into biodegradable plastic. \u00a9 Georgina Gregory from bath.ac.uk<\/p>\n
Researchers at Bath University have developed a process that allows the conversion of carbohydrate to deoxyribose and carbon dioxide into a cyclic carbonate that can be used as a monomer to produce biodegradable biocompatible polycarbonate plastics. The developed approach opens a new way of effective use of one of the greenhouse gases – carbon dioxide, as well as the way of obtaining less environmentally hazardous polymer materials from renewable raw materials.<\/p>\n
Polymers have proven themselves as a convenient construction material – lightweight, durable and durable. Now they are used almost everywhere – from food packaging to car bodies. However, with the launch in 1909 of the industrial production of the first synthetic polymer – bakelite, pollution began. After all, in living nature, there are almost no mechanisms capable of destroying the waste of synthetic polymers. For example, it may take up to four hundred years to completely destroy the polymers that most often clog up environmental systems – polyethylene, which goes to make bags and polyethylene terephthalate, from which plastic bottles are made.<\/p>\n
Therefore, recently more attention is paid to the development of methods for the synthesis of biodegradable polymer materials, preferably from renewable sources. The most famous of these materials is polylactic acid (polylactide), it can be used instead of polyethylene for the production of food film or bags.<\/p>\n
The development of a method for producing polylactic acid has become an important step towards “green polymers” – macromolecules, which will have a much more sparing impact on the environment than synthetic polymers. But she did not decide the question completely. At present, there is a huge amount of synthetic polymeric materials with different properties and applied in different areas, therefore the search for biodegradable analogs of polymers that differ in properties from polyethylene does not lose relevance.<\/p>\n
The aim of the researchers at Bath University was to develop biodegradable polymers of another type – polycarbonates. Of these, you can make not only garden greenhouses and CDs, but also elements of tourist equipment (for example, straps of backpacks on the basis of thin fibers woven from polycarbonate yarns). The polycarbonates currently manufactured by industry are not biodegradable, as are polyethylene with polytetra phthalate. In addition, the raw material for their production is bisphenol A, unsafe for human health.<\/p>\n
In the beginning of 2010 there were the first reports on the synthesis of polycarbonates from sugars, and the polycarbonates obtained turned out to be biodegradable. However, the synthesis method did not become safer: carbohydrate carbonates were obtained by the interaction of carbohydrates and phosgene COCl2 (see W. Zhu et al., 2011. High-molecular-weight aliphatic polycarbonates by melt polycondensation of dimethyl carbonate and aliphatic diols: synthesis and characterization), and Phosgene, although used in various fields of chemical synthesis, is notoriously known as a warfare agent of suffocating action, used during the First World War; It is also toxic in small quantities.<\/p>\n
However, from the point of view of chemistry, carbonates (inorganic and organic, low-molecular and high-molecular), and phosgene, and carbon dioxide are derivatives of carbonic acid H2CO3. British chemists have found a way to produce carbohydrate polycarbonates, which allows to replace toxic phosgene (carbonic acid chloride) with less dangerous carbon dioxide (carbonic anhydride).<\/p>\n
The essence of the developed method is as follows (Fig. 2). In the first stage, the monosaccharide in solution reacts with carbon dioxide gas passed through this solution, forming a cyclic carbonate (monosaccharide and carbonic acid ester) at room temperature. The latter serves as a monomer for the synthesis of polycarbonate. In a second step, the carbonate monomer enters the polymerization reaction with the opening of the ring and the desired high molecular weight polycarbonate compound is obtained. The formation of the polymer also proceeds under mild conditions (room temperature, small concentrations of catalyst and initiator), and a sample of polycarbonate with a molecular weight of 25,000 daltons takes no more than an hour.<\/p>\n
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Fig. 2. Scheme for the preparation of a polycarbonate polymer from deoxyribose and carbon dioxide. Figure from the discussed article in Polymer Chemistry<\/p>\n
The physical properties of the polymer obtained from the monosaccharide (for the development of the synthesis conditions, the researchers used deoxyribose) and carbon dioxide, were almost the same as polycarbonates obtained from petroleum products. The new polymer is transparent, highly resistant, resistant to mechanical contact damage. Its main difference from polycarbonates obtained on the basis of bisphenol A is that the action of enzymes released by soil bacteria destroys it to the original compounds – monosaccharide and inorganic salts of carbonic acid – carbonates. Carbonates accumulate in the soil and then either form limestone, or with groundwater flow into the World Ocean. Monosaccharides are used by soil organisms.<\/p>\n
Carbohydrate polycarbonate in the future can be used in the manufacture of food containers or bottles for baby food. And the biocompatibility of this plastic can be used in surgery or regenerative medicine, where it will be possible to make suture material, implants or even templates for growing tissues or organs intended for transplantation. The possibility of application in medical technologies is also conditioned by the fact that the properties of the new polymer can be easily adjusted, making changes in its structure. For example, using a chemical modification that does not affect biocompatibility, it can be achieved that a positive charge is concentrated on the filament of the carbohydrate polycarbonate macromolecule, which facilitates the cells of the tissue grown interacting with the pattern that directs growth. On the membranes of cells, a negative charge is localized. Cells will be “glued” to such a pattern due to the attraction of different charges.<\/p>\n
Having worked out the protocol for the synthesis of carbohydrate polycarbonate on D-deoxyribose (thymine) carbohydrate, the remainder of which is part of the DNA, British specialists on high-molecular compounds plan to test it on other carbohydrates – ribose and mannose. They say that after a century, during which organic synthesis developed, starting from the idea of \u200b\u200bconverting refined products, it is time to return to the synthesis substances obtained from renewable sources, the same carbohydrates, extracted from natural raw materials. Polymers derived from such raw materials will be classified as synthetic, because natural polymers are only those macromolecules that are formed directly as a result of the activity of living organisms. However, their building blocks, taken from wildlife, will facilitate their biodegradability, and a package of such polymer, hitting the environment, will disintegrate in one to two years, not hundreds of years, like polyethylene.<\/p>\n
The discovery of chemists from Bath makes us a step closer to the world without landfills for the disposal of plastic waste and natural landscapes contaminated with plastic bags and bottles. Received polycarbonate polymers, the raw materials for which are renewable sources – carbohydrates and carbon dioxide, decompose orders of magnitude faster than synthetic polymers from petroleum feedstocks.<\/p>\n
Source: Georgina L. Gregory, Gabriele Kociok-K\u00f6hn, Antoine Buchard. Polymers from sugars and CO2: ring-opening polymerization and copolymerization of cyclic carbonates derived from 2-deoxy-d-ribose. Polymer Chemistry. 2017. V. 8 (13). P. 2093-2104. DOI: 10.1039 \/ C7PY00236J.<\/p>","protected":false},"excerpt":{"rendered":"
Fig. 1. Graphic demonstration of a method developed by chemists from the University of Batsk to convert carbon dioxide and carbohydrates into biodegradable plastic. \u00a9 Georgina Gregory from bath.ac.uk Researchers at Bath University have developed a process that allows the conversion of carbohydrate to deoxyribose and carbon dioxide into a cyclic carbonate that can be […]<\/p>\n