Green Polymeric Materials and Sustainable Valorization of Natural Resources

Dear Colleagues,

The application of Green Chemistry concept in industrial chemistry, and particularly in the production and use of polymeric materials aims at reducing the manipulation and formation of hazardous substances during their production and life cycle. The above goals are usually achieved with the use of renewable raw materials and eco-friendly solvents, along with “green” product design and impact including safety, sustainability, degradation and recyclability. Furthermore, benign synthesis and catalysis, solvent-free processes, process design and intensification, as well as energy use issues are of crucial importance in the manufacturing of green and sustainable polymeric materials.

Over the past few decades, the production and applications of synthetic polymers showed an exponential increase. Recently, concerns regarding depletion of fossil resources, disposal-related issues, as well as government policies, have led to a continuously growing interest in the development of green, sustainable and safe environmentally-friendly plastics from renewable resources.

In general, there are three key approaches towards green plastics. The first approach is associated with the biorefinery concept, applying sustainable processes and using biomass from feedstocks. Renewable polymers are isolated from natural biopolymers or synthesized from biobased monomers. Carbohydrates such as cellulose, lignin, starch, terpenes, proteins, chitosan, and biopolyesters can be chemically modified. In fact, efforts are being made to synthesize traditional monomers and platform chemicals from renewable resources. Thus, ethylene, propylene, as well as butadiene can be produced from bioethanol. Diols, such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, and also polyols, diacids, etc., are also available nowadays. In this way, traditional polymers, such as polyethylene, polypropylene, poly(ethylene terephthalate), or polystyrene, can be now considered biobased. In addition, novel biobased thermoplastic and thermoset polymers have gained increasing interest. Organic acid monomers from renewable resources include glycolic, 3-hydroxypropionic, lactic, succinic, itaconic, muconic, adipic, levulinic, vanillic and 2,5-furandicarboxylic acids, while important alcohol monomers such as isosorbide, xylitol, sorbitol, glycerol can be derived from sugars.

Poly(ethylene 2,5-furandicarboxylate) (PEF) is a typical example of a new recyclable and fully biobased thermoplastic polymer. The industrial production of PEF is associated with reduced non-renewable energy use, low carbon footprint and atom economy. Furthermore, biodegradable polymers, such as poly(hydroxybutyrate) (PHB), poly(lactic acid) (PLA), poly(butylene succinate) (PBS), chitosan and others, are of special importance among sustainable polymers from renewable resources, considering the end of their life cycle.

The biotechnology approach uses living cells to produce biopolymers by essentially converting them into solar power reactors. Recent research efforts have shown that it is possible to create synthetic polymers within living cells, thus opening up a new area of chemical biology.

Finally, green polymers can be produced by activating and polymerizing carbon dioxide. For example, carbon dioxide can react with oxiranes, to produce cyclic carbonates. Eco-friendly materials such as non-isocyanate polyurethanes and polypropylene carbonate can be obtained.

The aim of this Special Issue is to highlight the progress on monomers from biorefinery, synthesis, industrial processes and benign catalysts, characterization, properties, applications, degradation, life cycle assessment, reuse and recycling of green and sustainable polymers, copolymers, blends and composites.

Prof. Dr. George Z. Papageorgiou
Dr. Dimitrios G. Papageorgiou
Guest Editors