Biodegradable polymer common classes

Table 1 Common classes and examples of biodegradable polymers...

Poly(hydroxyalkanoates) (PHAs) are a very common class of bacterial reserve materials, that have attracted considerable industrial attention (Anderson and Dawes, 1990). These polyesters are biodegradable and biocompatible thermoplastics with physical and mechanical properties dependent on their monomeric composition. The production of PHAs is a typical biotechnological process whose development requires the involvement of several scientific disciplines, i.e. genetics, biochemistry, microbiology, bioprocess engineering, polymer chemistry, and polymer engineering. 

Polylactides are linear polymers obtained from lactic acid, CHjCHOHCOOH, commonly known as poly(lactic acid) or polylactide. Lactic acid occurs naturally in animals and microorganisms and is found in many natural foods especially in fermented foods such as yogurt, buttermilk, sourdough breads, and sauerkraut [90, 91]. Besides being biodegradable, bioresorbable, and biocompatible, PLAs can be easily conformed by conventional thermoplastic melt processing, which makes this class of biodegradable polymers very suitable for uses in bionanocomposites. 

The primary obstacle to the widespread use of PLA and other biodegradable polymers has been that of high cost, a common problem associated with the introduction of new materials. However, the development of more efficient and economical synthesis and processing techniques has resulted in a significant reduction in the cost of this class of materials, making them more competitive with conventional petroleum-based polymers. 

Apart from the all-carbon backbone, poly(vinyl ester)s also exhibit a unique 1,3-diol structure (see Fig. 1). This structure is a common motif in many natural materials, e.g. carbohydrates. A number of oxidative or reductive electron transfer processes catalysed by natural redox systems are imaginable for this motif. The 1,3-diol structure is unique for a synthetic polymer and cannot be found in any other synthetic polymer class of significance. This explains the unusual biodegradation properties discussed below. 

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