Aliphatic Polyesters from Renewable Resources

Synthetic Strategies to Develop Aliphatic Polyesters Deriving from Renewable Resources... 

Lindblad M, Liu Y, Albertsson A-C, Ranucci E, Karlsson S (2002) Polymers from renewable resources. In Degradable aliphatic polyesters, vol. 157. Springer, Berlin, pp 139-161... 

It is an aliphatic polyester derived from renewable resources, such as com starch, tapioca roots, chips or starch, or sugarcane. Polylactic acid or polylactide (PLA) can withstand temperatures up to 110 °C [69]. PLA is soluble in chlorinated solvents, hot benzene, tetrahydrofuran, and dioxane [70]. It can be processed like other thermoplastics into fiber (for example, using conventional melt spinning processes) and film. Due to the chiral nature of lactic acid, several distinct forms of polylactide exist ... 

M.S. Lindblad, Y. Liu, A.-C. Albertsson, E. Ranucci, and S. Karlsson, "Polymers from renewable resources," in Degradable aliphatic polyesters, Advances in Polymer Science, pp. 139-161. Springer, Berlin, Heidelberg, 2001. 

PLA is an aliphatic polyester, derived from renewable resources, e. g. com starch or sugarcane sucrose. It is a pol)nner produced from lactic add (Figure 2), which is obtained from the fermentation of various carbohydrate spedes glucose, maltose and dextrose from corn or potato starch sucrose from beet or sugar cane and ladose from cheese whey [63]. 

Belonging to the family of aliphatic polyesters, poly(lactic acid) or polylactide (PLA) is composed of lactic acid repetitive units, which is the simplest ot-hydro)y acid with an asymmetric carbon atom. Interestingly, the L-lactic acid monomer, and more recently the D-lactic acid monomer, can be straightforwardly obtained by bacterial fermentation from renewable resources (namely starch), making both monomers and therefore the resulting polymers environmentally friendly. Polycondensation of lactic acid and ring-opening polymerization (ROP) of lactide (LA), i.e. cyclic diesters of lactic acid, are currently used to prepare PLA polymers (Scheme 4.1). 

Aliphatic thermoplastic polyesters represent a class of materials that is attracting a considerable amount of attention because they are i) biodegradable and biocompatible and ii) increasingly accessible from the exploitation of diols and dicarboxylic acids derived from renewable resources. If long methylene chains are present in the monomers, the ensuing products resemble polyethylene (PE) in strnctnre and, hence, in most properties, have the added advantage of biodegradability. 

Polylactic acid (PLA), the structure of which is shown in Figure 7.10, is a polyester fibre in which there has been recent interest because of its environmental credentials. PLA may be derived from renewable resources, such as cornstarch, and it is biodegradable. PLA may be coloured using certain disperse dyes, although the dyes do not exhaust as well as on PET, mainly because of its aliphatic character. Acrylic fibres are synthetic fibres based essentially on the addition polymer polyacrylonitrile, the essential structure of which is illustrated in Figure 7.11. However, most acrylic fibres are rather more complex and contain within their structure anionic groups, most commonly sulfonate (-SOs ), but also carboxylate (-CO2 ) groups either as a result of the incorporation of co-polymerised monomers in... 

Polylactic acid or polylactide (PLA) is a thermoplastic aliphatic polyester that can be derived from renewable resources, such as corn starch or sugarcanes. Although PLA has been known for more than a century, it has become of great commercial interest in recent years because of its renewability and degradability to natural metabolites. In addition, the properties of PLA can be varied over a wide range which makes it suitable to be used as a substitute to many petroleum based commodity plastics, such as polyolefins,... 

Another important class of natural biodegradable polymers is represented by the polyhydroxyalkanoates (PHA), a family of intracellular biopolymers synthesised by numerous bacteria as a reservoir of energy and carbon [19]. They are mainly produced via fermentation starting from renewable resources [20]. From a chemical point of view, PHA are aliphatic polyesters and represent some of the most easily biodegradable polymers found in nature. 

So far, wholly renewable biodegradable polyesters belong only to the aliphatic family, but efforts are being made to obtain aromatic dicarboxylic acids from renewable resources in order to fill this gap, as demonstrated by the research achievements involving aliphatic-aromatic copolyesters based on furandicarboxylic acid [59-61]. 

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