Advances in Biodegradable Polymers

Dear Colleagues,

Biodegradable polymers are polymers that can be subjected to significant changes in their chemical structure under certain environmental conditions in a relatively short time via natural biological processes, like the action of micro-organisms (mainly bacteria and fungi) resulting in a progressive reduction of their molecular weight and alteration of their physical properties. The mechanisms of biodegradable polymers include enzymatic degradation, hydrolysis and the combination of them, and is a surface or bulk erosion procedure. Enzymes are acting as biocatalysts. The process of biodegradation can be divided into three stages: biodeterioration, biofragmentation, and assimilation, leading to harmless and simple products (mainly CO₂ and H₂O after completely biodegradation), thus reducing the need to create a disposal system that causes harm to thr environment. The biodegradation rate depends either on external factors like temperature, oxygen, water and light or on internal ones, such as the chemical structure of polymers, their molecular weight, degree of crystallinity and hydrophilicity.

Biodegradable polymers are divided into two main categories: (a) Natural polymers obtained from natural resources during the growth cycles of all organisms, that are generally non-toxic and abundant, such as polysaccharides (chitosan, starch, cellulose, dextran, etc.), and proteins (collagen, fibrin, albumin, etc.), and (b) synthetic biodegradable polymers prepared by ring opening polymerization of cyclic esters and/or by melt polycondensation procedure, including aliphatic polyesters like poly(lactic  acid), poly(glycolic acid), poly(ε-caprolactone), poly(butylene succinate) and others, such as polyanhydrides, polyphosphazenes, polyurethanes, poly(hydroxy alkanoates) produced by microogranisms etc. This class of polymers bears many advantages compared to non-degradable polymers. They are readily and abundantly available (especially natural polymers), comparatively inexpensive, they can be modified to obtain semi-synthetic forms with new properties, whereas synthetic biodegradable polymers can be shortly degraded into nontoxic products. 

In recent years, due to the major environmental problems caused by the use of non-degradable polymers, biodegradable polymers have been increasingly gaining great interest. Biodegradable polyesters can be prepared naturally or by monomers derived from renewable sources. Natural polymers are completely biodegradable within a very short time, which is their key advantage, and they have high molecular weight. Aliphatic polyesters have also many benefits, being completely compostable or biodegradable, with no additional CO₂ emissions after their complete biodegradation. The lattest are thermoplastic materials, completely recyclable and can be used in several applications like food packaging, single-use items, 3D printing, waste water treatment, cosmetics, drug delivery, biomedicine, tissue engineering, surgery, etc.

The aim of this Special Issue is to highlight the progress and fundamental aspects of the synthesis, characterization, properties, and applications of biodegrable polymers, as well as their copolymers, composites, and nanocomposites in several scientific fields. Scientific works and mostly short reviews are warmly welcome. 

Prof. Dr. Dimitrios Bikiaris
Guest Editor

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