Fast and solvent free polymerization of carbohydrates induced by non-thermal atmospheric plasma

Abstract

Non-thermal atmospheric plasma (NTAP) is a physical technology that has been previously employed for surface treatment (cleaning, coating, erosion, etc.) and water or air depollution. We show here that, beyond surface effects, NTAP is capable of enabling the complete and fast polymerization of various mono- and disaccharides in the solid state within only a few minutes and at low temperature (40-80 °C). NTAP-induced polymerization involves a radical mechanism and yields water soluble polysaccharides with a mean molar mass of up to 100000 g mol and a mean hydrodynamic radius of 3 nm. Although polymerization reactions promoted by NTAP occurs in a random manner, the α-1,6 and β-1,6 linkages are however dominant. Furthermore, we discovered that NTAP is highly selective, strongly favoring glycosylation over other chemical transformations in the bulk. Under our working conditions, glycosyl units are preserved that constitute the repeating units of the polysaccharide product. No chemical degradation (e.g. intramolecular dehydration reactions) was observed, allowing a white powder to be recovered with a yield higher than 93 wt%. From a practical point of view, NTAP has great potential for breakthrough in the production of polysaccharides, notably because it does not require the use of a solvent or catalyst, thus by-passing the traditional post-treatment of aqueous effluents and catalyst recycling characteristic of biotechnological polysaccharide production. Its efficiency at low temperature also prevents carbohydrates from degradation. Finally, NTAP proceeds on an on/off switch basis, allowing the polymerization reaction to be started and stopped quasi instantaneously.