Monomers, polymerized renewable resources

There are certain similarities in the structures of synthetic and natural polymers such as nylon and protein, synthetic and natural rubbers, but sometimes the breadth of function is far greater in natural polymers. For example spider silk has the strength of Kevlar combined with greater stretch [17]. Several polymers may also be produced by modification of natural polymers or polymerization of monomers from renewable resources. 

In various areas of step-growth polymerization, the past 20 years have seen increasing interest in monomers from renewable resources. An early example, namely a patent of 1962 [17] describes syntheses of UPs from maleic anhydride and mixtures of isosorbide and other diols. Isosorbide is synthesized from glucose and can technically be produced at relatively low costs, when quantities of 50,000 tons or more are needed. 

Carbon dioxide is a widely available, inexpensive, and renewable resource. Hence, its utilization as a source of chemical carbon or as a solvent in chemical synthesis can lead to less of an impact on the environment than alternative processes. The preparation of aliphatic polycarbonates via the coupling of epoxides or oxetanes with CO2 illustrates processes where carbon dioxide can serve in both capacities, i.e., as a monomer and as a solvent. The reactions represented in (1) and (2) are two of the most well-studied instances of using carbon dioxide in chemical synthesis of polymeric materials, and represent environmentally benign routes to these biodegradable polymers. We and others have comprehensively reviewed this important area of chemistry fairly recently. Nevertheless, because of the intense interest and activity in this discipline, regular updates are warranted. 

The results reported demonstrate the feasibility of using monomers derived from renewable resources to build up new polymeric structures endowed with a variety of physical and mechanical properties which make them appealing for practical applications. 

Fossil based raw materials, mainly oil, gas and occasionally coal, are used almost exclusively for the manufacture of monomers. Plant materials, the so-called renewable resources, have been used earlier and could become more significant once again in the future. Although the plastics in these cases are obtained by direct polymerization of their monomers, the synthesis of the monomers themselves often requires several intermediate steps. The multi-functional multiple intermediate compounds in the plastic synthesis steps cannot be clearly defined as monomers in every case. The poly-con-... 

The purpose of this chapter is to provide a concise assessment of the state of the art related to the realm of monomers and macromonomers from renewable resources and their polymerization, and to offer some considerations about the prospective medium-term development of its various topics, which are also the section headings. Natural polymers are not covered here, nor are monomers like lactide, which are discussed elsewhere in the book. The reader interested in more comprehensive information on any of these topics, will find it in a recent comprehensive monograph [3],... 

Polymers derived from renewable resources (biopolymers) are broadly classified according to the method of production (1) Polymers directly extracted/ removed from natural materials (mainly plants) (e.g. polysaccharides such as starch and cellulose and proteins such as casein and wheat gluten), (2) polymers produced by "classical" chemical synthesis from renewable bio-derived monomers [e.g. poly(lactic acid), poly(glycolic acid) and their biopolyesters polymerized from lactic/glycolic acid monomers, which are produced by fermentation of carbohydrate feedstock] and (3) polymers produced by microorganisms or genetically transformed bacteria [e.g. the polyhydroxyalkanoates, mainly poly(hydroxybutyrates) and copolymers of hydroxybutyrate (HB) and hydroxyvalerate (HV)] [4]. 

As two non-petroleum chemicals readily accessible from renewable resources, both furfural and HMF are suitable starting materials for the preparation of versatile fine chemicals [14, 102-106] and can also serve as renewable monomers for preparation of sustainable polymer products [107]. Schemes 3, 4, and 5 depict the stmctures of the selected furan-based monomers [107-113]. As a typical precursor, furfural can be converted to a vast array of furan-based monomers bearing a moiety which can normally be polymerized by chain-growth polymerization mechanisms [108-113]. As shown in Scheme 3, these monomers are all readily polymerizable by chain-growth reactions. However, depending on their specific structure, the nature of the polymerization mechanism is different, ranging from free radical, cationic, anionic, to stereospecific initiation [108-113]. On the other hand, furfuryl... 

The progress of chemistry, associated with the industrial revolution, created a new scope for the preparation of novel polymeric materials based on renewable resources, first through the chemical modification of natural polymers from the mid-nineteenth century, which gave rise to the first commercial thermoplastic materials, like cellulose acetate and nitrate and the first elastomers, through the vulcanization of natural rubber. Later, these processes were complemented by approaches based on the controlled polymerization of a variety of natural monomers and oligomers, including terpenes, polyphenols and rosins. A further development called upon chemical technologies which transformed renewable resources to produce novel monomeric species like furfuryl alcohol. 

Sustained efforts have been extensively devoted to prepare new polymers based on renewable resources and with higher degradability. Of the different natural sources, carbohydrates stand out as highly convenient raw materials because they are inexpensive, readily available, and provide great stereochemical diversity. This chapter describes the potential of sugar-based monomers as precursors to a wide variety of macromolecular materials, with particular emphasis on both the mechanisms of polymerization and the properties of the ensuing products. 

The purpose of this chapter is to deal exclusively with the use of furan conqtounds and the exploitation of specific features related to furan chemistry with the aim of synthesizing polymeric materials. Imphcit in this treatment is the fact that vegetable renewable resources, in the form of mono, oligo and polysaccharides, are excellent sources of two first generation furans which, in turn, represent sources of a variety of monomers and other derivatives relevant to polymer synthesis. Although this topic has been reviewed on previous occasions [4], important advances have enriched it in recent years. An attempt will therefore be made to provide here a balanced treatment covering both the most salient achievements reported in the past several decades and novel promising contributions and perspectives. 

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). 

Although PLA is synthesized from renewable resources, the production of the polymeric form requires much processing, energy, and fuel. If a highly selective depolymerization of PLA to the cyclic monomer, lactide, can be achieved effectively, it will then become possible to renew PLA by the shortest, most energy-efficient route. 

Conventional processes for the production of 1,4-butanediol use fossil fuel feedstocks such as acetylene and formaldehyde. The biobased process involves the use of glucose from renewable resources to produce succinic acid followed by a chemical reduction to produce butanediol. PBS is produced by transesterification, direct polymerization, and condensation polymerization reactions. PBS copolymers can be produced by adding a third monomer such as sebacic acid, adipic acid and succinic acid, which is also produced by renewable resources [34]. 

The organochemical structures of annually renewable resources range from simple chemical structures to complex structures that are not easily duplicated in the test tube. The natural polymers useful for industrial applications include cellulose, starch, and protein. Cellulose is a polysaccharide with glucose linked as in cellobiose. Cellulose usually occurs in a fibrous form. Starch is also a carbohydrate polymeric compound that consists of both linear polymer and branched polymer end occurs in granules in plants. Proteins are found both in plants and animals. Fats and oils and sugars are usually monomers and have a range of compositions and properties. 

Due to abundantly available feedstock and low cost, poly lactic acid (PLA) is one of the most promising bio-based polymers. PLA is obtained by the controlled polymerization of lactic acid monomers which in turn are obtained from renewable resources such as sugar feedstock, wheat, maize, com, and waste products from food or agriculture industry by fermentation (Siracusa et al., 2008). Properties of PLA vary according to the Z - to - D lactylenantiomeric ratio. Table 8 lists some important properties of PLA. 

Andrzej Duda is head of the Department of Polymer Chemistry at the Center of Molecular and Macromolecular Studies of the Polish Academy of Sciences in Lodz, Poland and currently chairman of the Polymer Section of the Polish Chemical Society as well as a member of the Polish National Science Center. He received his MSc degree from Lodz Univereity of Technology (1975), his PhD (1984, under the supervision of Stanislaw Penczek), and his DSc (1997) from the Polish Academy of Sciences. Since 2004, he has been a full professor in chemistry with the title conferred by the President of Republic of Poland. His research interests focus on thermodynamics, kinetics, and mechanisms of the ring-opening and ionic polymerizations, reactivity-selectivity relationships in polymerization, methods of controlled/living polymerization, macromolecular engineering, and polymers and monomers available from renewable resources. He is the author and coauthor of more than 100 scientific papers (including 5 book chapters). 

The fact that similar monomers are available from renewable and fossil resources permits the polymers currently in vogue to be continued. The monomers are identified as those predominantly used in condensation polymerization. Monomers from natural resources currently available by... 

Poly(lactic acid), produced by Nature Works LLC, is another example for a hybrid process, in which the monomer, lactic acid is produced by fermentation of com using lactobacilli. The subsequent polymerization is accomplished either by anionic ring-opening polymerization of the lactide dimer, or more recently by an azeotropic dehydration condensation, a chemical process. Cargill Dow now has shown that the polylactic acid produced by it s subsidiary NatureWorks LLC, is fully competitive with its synthetic counterparts, and fibers can also be melt-spun from this polymer. These Ingeo fibers are world s first man made fiber made from 100% atmually renewable resources. [12]. 

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